zte's code,first commit
Change-Id: I9a04da59e459a9bc0d67f101f700d9d7dc8d681b
diff --git a/ap/os/linux/linux-3.4.x/mm/vmscan.c b/ap/os/linux/linux-3.4.x/mm/vmscan.c
new file mode 100644
index 0000000..5888e29
--- /dev/null
+++ b/ap/os/linux/linux-3.4.x/mm/vmscan.c
@@ -0,0 +1,3745 @@
+/*
+ * linux/mm/vmscan.c
+ *
+ * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
+ *
+ * Swap reorganised 29.12.95, Stephen Tweedie.
+ * kswapd added: 7.1.96 sct
+ * Removed kswapd_ctl limits, and swap out as many pages as needed
+ * to bring the system back to freepages.high: 2.4.97, Rik van Riel.
+ * Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com).
+ * Multiqueue VM started 5.8.00, Rik van Riel.
+ */
+
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/gfp.h>
+#include <linux/kernel_stat.h>
+#include <linux/swap.h>
+#include <linux/pagemap.h>
+#include <linux/init.h>
+#include <linux/highmem.h>
+#include <linux/vmstat.h>
+#include <linux/file.h>
+#include <linux/writeback.h>
+#include <linux/blkdev.h>
+#include <linux/buffer_head.h> /* for try_to_release_page(),
+ buffer_heads_over_limit */
+#include <linux/mm_inline.h>
+#include <linux/backing-dev.h>
+#include <linux/rmap.h>
+#include <linux/topology.h>
+#include <linux/cpu.h>
+#include <linux/cpuset.h>
+#include <linux/compaction.h>
+#include <linux/notifier.h>
+#include <linux/rwsem.h>
+#include <linux/delay.h>
+#include <linux/kthread.h>
+#include <linux/freezer.h>
+#include <linux/memcontrol.h>
+#include <linux/delayacct.h>
+#include <linux/sysctl.h>
+#include <linux/oom.h>
+#include <linux/prefetch.h>
+#include <linux/debugfs.h>
+
+#include <asm/tlbflush.h>
+#include <asm/div64.h>
+
+#include <linux/swapops.h>
+
+#include "internal.h"
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/vmscan.h>
+
+/*
+ * reclaim_mode determines how the inactive list is shrunk
+ * RECLAIM_MODE_SINGLE: Reclaim only order-0 pages
+ * RECLAIM_MODE_ASYNC: Do not block
+ * RECLAIM_MODE_SYNC: Allow blocking e.g. call wait_on_page_writeback
+ * RECLAIM_MODE_LUMPYRECLAIM: For high-order allocations, take a reference
+ * page from the LRU and reclaim all pages within a
+ * naturally aligned range
+ * RECLAIM_MODE_COMPACTION: For high-order allocations, reclaim a number of
+ * order-0 pages and then compact the zone
+ */
+typedef unsigned __bitwise__ reclaim_mode_t;
+#define RECLAIM_MODE_SINGLE ((__force reclaim_mode_t)0x01u)
+#define RECLAIM_MODE_ASYNC ((__force reclaim_mode_t)0x02u)
+#define RECLAIM_MODE_SYNC ((__force reclaim_mode_t)0x04u)
+#define RECLAIM_MODE_LUMPYRECLAIM ((__force reclaim_mode_t)0x08u)
+#define RECLAIM_MODE_COMPACTION ((__force reclaim_mode_t)0x10u)
+
+struct scan_control {
+ /* Incremented by the number of inactive pages that were scanned */
+ unsigned long nr_scanned;
+
+ /* Number of pages freed so far during a call to shrink_zones() */
+ unsigned long nr_reclaimed;
+
+ /* How many pages shrink_list() should reclaim */
+ unsigned long nr_to_reclaim;
+
+ unsigned long hibernation_mode;
+
+ /* This context's GFP mask */
+ gfp_t gfp_mask;
+
+ int may_writepage;
+
+ /* Can mapped pages be reclaimed? */
+ int may_unmap;
+
+ /* Can pages be swapped as part of reclaim? */
+ int may_swap;
+
+ int order;
+
+ /*
+ * Intend to reclaim enough continuous memory rather than reclaim
+ * enough amount of memory. i.e, mode for high order allocation.
+ */
+ reclaim_mode_t reclaim_mode;
+
+ /*
+ * The memory cgroup that hit its limit and as a result is the
+ * primary target of this reclaim invocation.
+ */
+ struct mem_cgroup *target_mem_cgroup;
+
+ /*
+ * Nodemask of nodes allowed by the caller. If NULL, all nodes
+ * are scanned.
+ */
+ nodemask_t *nodemask;
+};
+
+struct mem_cgroup_zone {
+ struct mem_cgroup *mem_cgroup;
+ struct zone *zone;
+};
+
+#define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
+
+#ifdef ARCH_HAS_PREFETCH
+#define prefetch_prev_lru_page(_page, _base, _field) \
+ do { \
+ if ((_page)->lru.prev != _base) { \
+ struct page *prev; \
+ \
+ prev = lru_to_page(&(_page->lru)); \
+ prefetch(&prev->_field); \
+ } \
+ } while (0)
+#else
+#define prefetch_prev_lru_page(_page, _base, _field) do { } while (0)
+#endif
+
+#ifdef ARCH_HAS_PREFETCHW
+#define prefetchw_prev_lru_page(_page, _base, _field) \
+ do { \
+ if ((_page)->lru.prev != _base) { \
+ struct page *prev; \
+ \
+ prev = lru_to_page(&(_page->lru)); \
+ prefetchw(&prev->_field); \
+ } \
+ } while (0)
+#else
+#define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0)
+#endif
+
+/*
+ * From 0 .. 100. Higher means more swappy.
+ */
+int vm_swappiness = 60;
+long vm_total_pages; /* The total number of pages which the VM controls */
+
+static LIST_HEAD(shrinker_list);
+static DECLARE_RWSEM(shrinker_rwsem);
+
+#ifdef CONFIG_CGROUP_MEM_RES_CTLR
+static bool global_reclaim(struct scan_control *sc)
+{
+ return !sc->target_mem_cgroup;
+}
+
+static bool scanning_global_lru(struct mem_cgroup_zone *mz)
+{
+ return !mz->mem_cgroup;
+}
+#else
+static bool global_reclaim(struct scan_control *sc)
+{
+ return true;
+}
+
+static bool scanning_global_lru(struct mem_cgroup_zone *mz)
+{
+ return true;
+}
+#endif
+
+static struct zone_reclaim_stat *get_reclaim_stat(struct mem_cgroup_zone *mz)
+{
+ if (!scanning_global_lru(mz))
+ return mem_cgroup_get_reclaim_stat(mz->mem_cgroup, mz->zone);
+
+ return &mz->zone->reclaim_stat;
+}
+
+static unsigned long zone_nr_lru_pages(struct mem_cgroup_zone *mz,
+ enum lru_list lru)
+{
+ if (!scanning_global_lru(mz))
+ return mem_cgroup_zone_nr_lru_pages(mz->mem_cgroup,
+ zone_to_nid(mz->zone),
+ zone_idx(mz->zone),
+ BIT(lru));
+
+ return zone_page_state(mz->zone, NR_LRU_BASE + lru);
+}
+
+struct dentry *debug_file;
+
+static int debug_shrinker_show(struct seq_file *s, void *unused)
+{
+ struct shrinker *shrinker;
+ struct shrink_control sc;
+
+ sc.gfp_mask = -1;
+ sc.nr_to_scan = 0;
+
+ down_read(&shrinker_rwsem);
+ list_for_each_entry(shrinker, &shrinker_list, list) {
+ char name[64];
+ int num_objs;
+
+ num_objs = shrinker->shrink(shrinker, &sc);
+ seq_printf(s, "%pf %d\n", shrinker->shrink, num_objs);
+ }
+ up_read(&shrinker_rwsem);
+ return 0;
+}
+
+static int debug_shrinker_open(struct inode *inode, struct file *file)
+{
+ return single_open(file, debug_shrinker_show, inode->i_private);
+}
+
+static const struct file_operations debug_shrinker_fops = {
+ .open = debug_shrinker_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = single_release,
+};
+
+/*
+ * Add a shrinker callback to be called from the vm
+ */
+void register_shrinker(struct shrinker *shrinker)
+{
+ atomic_long_set(&shrinker->nr_in_batch, 0);
+ down_write(&shrinker_rwsem);
+ list_add_tail(&shrinker->list, &shrinker_list);
+ up_write(&shrinker_rwsem);
+}
+EXPORT_SYMBOL(register_shrinker);
+
+static int __init add_shrinker_debug(void)
+{
+ debugfs_create_file("shrinker", 0644, NULL, NULL,
+ &debug_shrinker_fops);
+ return 0;
+}
+
+late_initcall(add_shrinker_debug);
+
+/*
+ * Remove one
+ */
+void unregister_shrinker(struct shrinker *shrinker)
+{
+ down_write(&shrinker_rwsem);
+ list_del(&shrinker->list);
+ up_write(&shrinker_rwsem);
+}
+EXPORT_SYMBOL(unregister_shrinker);
+
+static inline int do_shrinker_shrink(struct shrinker *shrinker,
+ struct shrink_control *sc,
+ unsigned long nr_to_scan)
+{
+ sc->nr_to_scan = nr_to_scan;
+ return (*shrinker->shrink)(shrinker, sc);
+}
+
+#define SHRINK_BATCH 128
+/*
+ * Call the shrink functions to age shrinkable caches
+ *
+ * Here we assume it costs one seek to replace a lru page and that it also
+ * takes a seek to recreate a cache object. With this in mind we age equal
+ * percentages of the lru and ageable caches. This should balance the seeks
+ * generated by these structures.
+ *
+ * If the vm encountered mapped pages on the LRU it increase the pressure on
+ * slab to avoid swapping.
+ *
+ * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits.
+ *
+ * `lru_pages' represents the number of on-LRU pages in all the zones which
+ * are eligible for the caller's allocation attempt. It is used for balancing
+ * slab reclaim versus page reclaim.
+ *
+ * Returns the number of slab objects which we shrunk.
+ */
+unsigned long shrink_slab(struct shrink_control *shrink,
+ unsigned long nr_pages_scanned,
+ unsigned long lru_pages)
+{
+ struct shrinker *shrinker;
+ unsigned long ret = 0;
+
+ if (nr_pages_scanned == 0)
+ nr_pages_scanned = SWAP_CLUSTER_MAX;
+
+ if (!down_read_trylock(&shrinker_rwsem)) {
+ /* Assume we'll be able to shrink next time */
+ ret = 1;
+ goto out;
+ }
+
+ list_for_each_entry(shrinker, &shrinker_list, list) {
+ unsigned long long delta;
+ long total_scan;
+ long max_pass;
+ int shrink_ret = 0;
+ long nr;
+ long new_nr;
+ long batch_size = shrinker->batch ? shrinker->batch
+ : SHRINK_BATCH;
+
+ max_pass = do_shrinker_shrink(shrinker, shrink, 0);
+ if (max_pass <= 0)
+ continue;
+
+ /*
+ * copy the current shrinker scan count into a local variable
+ * and zero it so that other concurrent shrinker invocations
+ * don't also do this scanning work.
+ */
+ nr = atomic_long_xchg(&shrinker->nr_in_batch, 0);
+
+ total_scan = nr;
+ delta = (4 * nr_pages_scanned) / shrinker->seeks;
+ delta *= max_pass;
+ do_div(delta, lru_pages + 1);
+ total_scan += delta;
+ if (total_scan < 0) {
+ printk(KERN_ERR "shrink_slab: %pF negative objects to "
+ "delete nr=%ld\n",
+ shrinker->shrink, total_scan);
+ total_scan = max_pass;
+ }
+
+ /*
+ * We need to avoid excessive windup on filesystem shrinkers
+ * due to large numbers of GFP_NOFS allocations causing the
+ * shrinkers to return -1 all the time. This results in a large
+ * nr being built up so when a shrink that can do some work
+ * comes along it empties the entire cache due to nr >>>
+ * max_pass. This is bad for sustaining a working set in
+ * memory.
+ *
+ * Hence only allow the shrinker to scan the entire cache when
+ * a large delta change is calculated directly.
+ */
+ if (delta < max_pass / 4)
+ total_scan = min(total_scan, max_pass / 2);
+
+ /*
+ * Avoid risking looping forever due to too large nr value:
+ * never try to free more than twice the estimate number of
+ * freeable entries.
+ */
+ if (total_scan > max_pass * 2)
+ total_scan = max_pass * 2;
+
+ trace_mm_shrink_slab_start(shrinker, shrink, nr,
+ nr_pages_scanned, lru_pages,
+ max_pass, delta, total_scan);
+
+ while (total_scan >= batch_size) {
+ int nr_before;
+
+ nr_before = do_shrinker_shrink(shrinker, shrink, 0);
+ shrink_ret = do_shrinker_shrink(shrinker, shrink,
+ batch_size);
+ if (shrink_ret == -1)
+ break;
+ if (shrink_ret < nr_before)
+ ret += nr_before - shrink_ret;
+ count_vm_events(SLABS_SCANNED, batch_size);
+ total_scan -= batch_size;
+
+ cond_resched();
+ }
+
+ /*
+ * move the unused scan count back into the shrinker in a
+ * manner that handles concurrent updates. If we exhausted the
+ * scan, there is no need to do an update.
+ */
+ if (total_scan > 0)
+ new_nr = atomic_long_add_return(total_scan,
+ &shrinker->nr_in_batch);
+ else
+ new_nr = atomic_long_read(&shrinker->nr_in_batch);
+
+ trace_mm_shrink_slab_end(shrinker, shrink_ret, nr, new_nr);
+ }
+ up_read(&shrinker_rwsem);
+out:
+ cond_resched();
+ return ret;
+}
+
+static void set_reclaim_mode(int priority, struct scan_control *sc,
+ bool sync)
+{
+ reclaim_mode_t syncmode = sync ? RECLAIM_MODE_SYNC : RECLAIM_MODE_ASYNC;
+
+ /*
+ * Initially assume we are entering either lumpy reclaim or
+ * reclaim/compaction.Depending on the order, we will either set the
+ * sync mode or just reclaim order-0 pages later.
+ */
+ if (COMPACTION_BUILD)
+ sc->reclaim_mode = RECLAIM_MODE_COMPACTION;
+ else
+ sc->reclaim_mode = RECLAIM_MODE_LUMPYRECLAIM;
+
+ /*
+ * Avoid using lumpy reclaim or reclaim/compaction if possible by
+ * restricting when its set to either costly allocations or when
+ * under memory pressure
+ */
+ if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
+ sc->reclaim_mode |= syncmode;
+ else if (sc->order && priority < DEF_PRIORITY - 2)
+ sc->reclaim_mode |= syncmode;
+ else
+ sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC;
+}
+
+static void reset_reclaim_mode(struct scan_control *sc)
+{
+ sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC;
+}
+
+static inline int is_page_cache_freeable(struct page *page)
+{
+ /*
+ * A freeable page cache page is referenced only by the caller
+ * that isolated the page, the page cache radix tree and
+ * optional buffer heads at page->private.
+ */
+ return page_count(page) - page_has_private(page) == 2;
+}
+
+static int may_write_to_queue(struct backing_dev_info *bdi,
+ struct scan_control *sc)
+{
+ if (current->flags & PF_SWAPWRITE)
+ return 1;
+ if (!bdi_write_congested(bdi))
+ return 1;
+ if (bdi == current->backing_dev_info)
+ return 1;
+
+ /* lumpy reclaim for hugepage often need a lot of write */
+ if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
+ return 1;
+ return 0;
+}
+
+/*
+ * We detected a synchronous write error writing a page out. Probably
+ * -ENOSPC. We need to propagate that into the address_space for a subsequent
+ * fsync(), msync() or close().
+ *
+ * The tricky part is that after writepage we cannot touch the mapping: nothing
+ * prevents it from being freed up. But we have a ref on the page and once
+ * that page is locked, the mapping is pinned.
+ *
+ * We're allowed to run sleeping lock_page() here because we know the caller has
+ * __GFP_FS.
+ */
+static void handle_write_error(struct address_space *mapping,
+ struct page *page, int error)
+{
+ lock_page(page);
+ if (page_mapping(page) == mapping)
+ mapping_set_error(mapping, error);
+ unlock_page(page);
+}
+
+/* possible outcome of pageout() */
+typedef enum {
+ /* failed to write page out, page is locked */
+ PAGE_KEEP,
+ /* move page to the active list, page is locked */
+ PAGE_ACTIVATE,
+ /* page has been sent to the disk successfully, page is unlocked */
+ PAGE_SUCCESS,
+ /* page is clean and locked */
+ PAGE_CLEAN,
+} pageout_t;
+
+/*
+ * pageout is called by shrink_page_list() for each dirty page.
+ * Calls ->writepage().
+ */
+static pageout_t pageout(struct page *page, struct address_space *mapping,
+ struct scan_control *sc)
+{
+ /*
+ * If the page is dirty, only perform writeback if that write
+ * will be non-blocking. To prevent this allocation from being
+ * stalled by pagecache activity. But note that there may be
+ * stalls if we need to run get_block(). We could test
+ * PagePrivate for that.
+ *
+ * If this process is currently in __generic_file_aio_write() against
+ * this page's queue, we can perform writeback even if that
+ * will block.
+ *
+ * If the page is swapcache, write it back even if that would
+ * block, for some throttling. This happens by accident, because
+ * swap_backing_dev_info is bust: it doesn't reflect the
+ * congestion state of the swapdevs. Easy to fix, if needed.
+ */
+ if (!is_page_cache_freeable(page))
+ return PAGE_KEEP;
+ if (!mapping) {
+ /*
+ * Some data journaling orphaned pages can have
+ * page->mapping == NULL while being dirty with clean buffers.
+ */
+ if (page_has_private(page)) {
+ if (try_to_free_buffers(page)) {
+ ClearPageDirty(page);
+ printk("%s: orphaned page\n", __func__);
+ return PAGE_CLEAN;
+ }
+ }
+ return PAGE_KEEP;
+ }
+ if (mapping->a_ops->writepage == NULL)
+ return PAGE_ACTIVATE;
+ if (!may_write_to_queue(mapping->backing_dev_info, sc))
+ return PAGE_KEEP;
+
+ if (clear_page_dirty_for_io(page)) {
+ int res;
+ struct writeback_control wbc = {
+ .sync_mode = WB_SYNC_NONE,
+ .nr_to_write = SWAP_CLUSTER_MAX,
+ .range_start = 0,
+ .range_end = LLONG_MAX,
+ .for_reclaim = 1,
+ };
+
+ SetPageReclaim(page);
+ res = mapping->a_ops->writepage(page, &wbc);
+ if (res < 0)
+ handle_write_error(mapping, page, res);
+ if (res == AOP_WRITEPAGE_ACTIVATE) {
+ ClearPageReclaim(page);
+ return PAGE_ACTIVATE;
+ }
+
+ if (!PageWriteback(page)) {
+ /* synchronous write or broken a_ops? */
+ ClearPageReclaim(page);
+ }
+ trace_mm_vmscan_writepage(page,
+ trace_reclaim_flags(page, sc->reclaim_mode));
+ inc_zone_page_state(page, NR_VMSCAN_WRITE);
+ return PAGE_SUCCESS;
+ }
+
+ return PAGE_CLEAN;
+}
+
+/*
+ * Same as remove_mapping, but if the page is removed from the mapping, it
+ * gets returned with a refcount of 0.
+ */
+static int __remove_mapping(struct address_space *mapping, struct page *page)
+{
+ BUG_ON(!PageLocked(page));
+ BUG_ON(mapping != page_mapping(page));
+
+ unsigned long flags;
+
+ spin_lock_irq(&mapping->tree_lock);
+ local_irq_save(flags);
+ /*
+ * The non racy check for a busy page.
+ *
+ * Must be careful with the order of the tests. When someone has
+ * a ref to the page, it may be possible that they dirty it then
+ * drop the reference. So if PageDirty is tested before page_count
+ * here, then the following race may occur:
+ *
+ * get_user_pages(&page);
+ * [user mapping goes away]
+ * write_to(page);
+ * !PageDirty(page) [good]
+ * SetPageDirty(page);
+ * put_page(page);
+ * !page_count(page) [good, discard it]
+ *
+ * [oops, our write_to data is lost]
+ *
+ * Reversing the order of the tests ensures such a situation cannot
+ * escape unnoticed. The smp_rmb is needed to ensure the page->flags
+ * load is not satisfied before that of page->_count.
+ *
+ * Note that if SetPageDirty is always performed via set_page_dirty,
+ * and thus under tree_lock, then this ordering is not required.
+ */
+ if (!page_freeze_refs(page, 2))
+ goto cannot_free;
+ /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */
+ if (unlikely(PageDirty(page))) {
+ page_unfreeze_refs(page, 2);
+ goto cannot_free;
+ }
+
+ if (PageSwapCache(page)) {
+ swp_entry_t swap = { .val = page_private(page) };
+ __delete_from_swap_cache(page);
+ local_irq_restore(flags);
+ spin_unlock_irq(&mapping->tree_lock);
+ swapcache_free(swap, page);
+ } else {
+ void (*freepage)(struct page *);
+
+ freepage = mapping->a_ops->freepage;
+
+ __delete_from_page_cache(page);
+ local_irq_restore(flags);
+ spin_unlock_irq(&mapping->tree_lock);
+ mem_cgroup_uncharge_cache_page(page);
+
+ if (freepage != NULL)
+ freepage(page);
+ }
+
+ return 1;
+
+cannot_free:
+ local_irq_restore(flags);
+ spin_unlock_irq(&mapping->tree_lock);
+ return 0;
+}
+
+/*
+ * Attempt to detach a locked page from its ->mapping. If it is dirty or if
+ * someone else has a ref on the page, abort and return 0. If it was
+ * successfully detached, return 1. Assumes the caller has a single ref on
+ * this page.
+ */
+int remove_mapping(struct address_space *mapping, struct page *page)
+{
+ if (__remove_mapping(mapping, page)) {
+ /*
+ * Unfreezing the refcount with 1 rather than 2 effectively
+ * drops the pagecache ref for us without requiring another
+ * atomic operation.
+ */
+ page_unfreeze_refs(page, 1);
+ return 1;
+ }
+ return 0;
+}
+
+/**
+ * putback_lru_page - put previously isolated page onto appropriate LRU list
+ * @page: page to be put back to appropriate lru list
+ *
+ * Add previously isolated @page to appropriate LRU list.
+ * Page may still be unevictable for other reasons.
+ *
+ * lru_lock must not be held, interrupts must be enabled.
+ */
+void putback_lru_page(struct page *page)
+{
+ int lru;
+ int active = !!TestClearPageActive(page);
+ int was_unevictable = PageUnevictable(page);
+
+ VM_BUG_ON(PageLRU(page));
+
+redo:
+ ClearPageUnevictable(page);
+
+ if (page_evictable(page, NULL)) {
+ /*
+ * For evictable pages, we can use the cache.
+ * In event of a race, worst case is we end up with an
+ * unevictable page on [in]active list.
+ * We know how to handle that.
+ */
+ lru = active + page_lru_base_type(page);
+ lru_cache_add_lru(page, lru);
+ } else {
+ /*
+ * Put unevictable pages directly on zone's unevictable
+ * list.
+ */
+ lru = LRU_UNEVICTABLE;
+ add_page_to_unevictable_list(page);
+ /*
+ * When racing with an mlock or AS_UNEVICTABLE clearing
+ * (page is unlocked) make sure that if the other thread
+ * does not observe our setting of PG_lru and fails
+ * isolation/check_move_unevictable_pages,
+ * we see PG_mlocked/AS_UNEVICTABLE cleared below and move
+ * the page back to the evictable list.
+ *
+ * The other side is TestClearPageMlocked() or shmem_lock().
+ */
+ smp_mb();
+ }
+
+ /*
+ * page's status can change while we move it among lru. If an evictable
+ * page is on unevictable list, it never be freed. To avoid that,
+ * check after we added it to the list, again.
+ */
+ if (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) {
+ if (!isolate_lru_page(page)) {
+ put_page(page);
+ goto redo;
+ }
+ /* This means someone else dropped this page from LRU
+ * So, it will be freed or putback to LRU again. There is
+ * nothing to do here.
+ */
+ }
+
+ if (was_unevictable && lru != LRU_UNEVICTABLE)
+ count_vm_event(UNEVICTABLE_PGRESCUED);
+ else if (!was_unevictable && lru == LRU_UNEVICTABLE)
+ count_vm_event(UNEVICTABLE_PGCULLED);
+
+ put_page(page); /* drop ref from isolate */
+}
+
+enum page_references {
+ PAGEREF_RECLAIM,
+ PAGEREF_RECLAIM_CLEAN,
+ PAGEREF_KEEP,
+ PAGEREF_ACTIVATE,
+};
+
+static enum page_references page_check_references(struct page *page,
+ struct mem_cgroup_zone *mz,
+ struct scan_control *sc)
+{
+ int referenced_ptes, referenced_page;
+ unsigned long vm_flags;
+
+ referenced_ptes = page_referenced(page, 1, mz->mem_cgroup, &vm_flags);
+ referenced_page = TestClearPageReferenced(page);
+
+ /* Lumpy reclaim - ignore references */
+ if (sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM)
+ return PAGEREF_RECLAIM;
+
+ /*
+ * Mlock lost the isolation race with us. Let try_to_unmap()
+ * move the page to the unevictable list.
+ */
+ if (vm_flags & VM_LOCKED)
+ return PAGEREF_RECLAIM;
+
+ if (referenced_ptes) {
+ if (PageSwapBacked(page))
+ return PAGEREF_ACTIVATE;
+ /*
+ * All mapped pages start out with page table
+ * references from the instantiating fault, so we need
+ * to look twice if a mapped file page is used more
+ * than once.
+ *
+ * Mark it and spare it for another trip around the
+ * inactive list. Another page table reference will
+ * lead to its activation.
+ *
+ * Note: the mark is set for activated pages as well
+ * so that recently deactivated but used pages are
+ * quickly recovered.
+ */
+ SetPageReferenced(page);
+
+ if (referenced_page || referenced_ptes > 1)
+ return PAGEREF_ACTIVATE;
+
+ /*
+ * Activate file-backed executable pages after first usage.
+ */
+ if (vm_flags & VM_EXEC)
+ return PAGEREF_ACTIVATE;
+
+ return PAGEREF_KEEP;
+ }
+
+ /* Reclaim if clean, defer dirty pages to writeback */
+ if (referenced_page && !PageSwapBacked(page))
+ return PAGEREF_RECLAIM_CLEAN;
+
+ return PAGEREF_RECLAIM;
+}
+
+/*
+ * shrink_page_list() returns the number of reclaimed pages
+ */
+static unsigned long shrink_page_list(struct list_head *page_list,
+ struct mem_cgroup_zone *mz,
+ struct scan_control *sc,
+ int priority,
+ unsigned long *ret_nr_dirty,
+ unsigned long *ret_nr_writeback)
+{
+ LIST_HEAD(ret_pages);
+ LIST_HEAD(free_pages);
+ int pgactivate = 0;
+ unsigned long nr_dirty = 0;
+ unsigned long nr_congested = 0;
+ unsigned long nr_reclaimed = 0;
+ unsigned long nr_writeback = 0;
+
+ cond_resched();
+
+ while (!list_empty(page_list)) {
+ enum page_references references;
+ struct address_space *mapping;
+ struct page *page;
+ int may_enter_fs;
+
+ cond_resched();
+
+ page = lru_to_page(page_list);
+ list_del(&page->lru);
+
+ if (!trylock_page(page))
+ goto keep;
+
+ VM_BUG_ON(PageActive(page));
+ VM_BUG_ON(page_zone(page) != mz->zone);
+
+ sc->nr_scanned++;
+
+ if (unlikely(!page_evictable(page, NULL)))
+ goto cull_mlocked;
+
+ if (!sc->may_unmap && page_mapped(page))
+ goto keep_locked;
+
+ /* Double the slab pressure for mapped and swapcache pages */
+ if (page_mapped(page) || PageSwapCache(page))
+ sc->nr_scanned++;
+
+ may_enter_fs = (sc->gfp_mask & __GFP_FS) ||
+ (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO));
+
+ if (PageWriteback(page)) {
+ nr_writeback++;
+ /*
+ * Synchronous reclaim cannot queue pages for
+ * writeback due to the possibility of stack overflow
+ * but if it encounters a page under writeback, wait
+ * for the IO to complete.
+ */
+ if ((sc->reclaim_mode & RECLAIM_MODE_SYNC) &&
+ may_enter_fs)
+ wait_on_page_writeback(page);
+ else {
+ unlock_page(page);
+ goto keep_lumpy;
+ }
+ }
+
+ references = page_check_references(page, mz, sc);
+ switch (references) {
+ case PAGEREF_ACTIVATE:
+ goto activate_locked;
+ case PAGEREF_KEEP:
+ goto keep_locked;
+ case PAGEREF_RECLAIM:
+ case PAGEREF_RECLAIM_CLEAN:
+ ; /* try to reclaim the page below */
+ }
+
+ /*
+ * Anonymous process memory has backing store?
+ * Try to allocate it some swap space here.
+ */
+ if (PageAnon(page) && !PageSwapCache(page)) {
+ if (!(sc->gfp_mask & __GFP_IO))
+ goto keep_locked;
+ if (!add_to_swap(page))
+ goto activate_locked;
+ may_enter_fs = 1;
+ }
+
+ mapping = page_mapping(page);
+
+ /*
+ * The page is mapped into the page tables of one or more
+ * processes. Try to unmap it here.
+ */
+ if (page_mapped(page) && mapping) {
+ switch (try_to_unmap(page, TTU_UNMAP)) {
+ case SWAP_FAIL:
+ goto activate_locked;
+ case SWAP_AGAIN:
+ goto keep_locked;
+ case SWAP_MLOCK:
+ goto cull_mlocked;
+ case SWAP_SUCCESS:
+ ; /* try to free the page below */
+ }
+ }
+
+ if (PageDirty(page)) {
+ nr_dirty++;
+
+ /*
+ * Only kswapd can writeback filesystem pages to
+ * avoid risk of stack overflow but do not writeback
+ * unless under significant pressure.
+ */
+ if (page_is_file_cache(page) &&
+ (!current_is_kswapd() || priority >= DEF_PRIORITY - 2)) {
+ /*
+ * Immediately reclaim when written back.
+ * Similar in principal to deactivate_page()
+ * except we already have the page isolated
+ * and know it's dirty
+ */
+ inc_zone_page_state(page, NR_VMSCAN_IMMEDIATE);
+ SetPageReclaim(page);
+
+ goto keep_locked;
+ }
+
+ if (references == PAGEREF_RECLAIM_CLEAN)
+ goto keep_locked;
+ if (!may_enter_fs)
+ goto keep_locked;
+ if (!sc->may_writepage)
+ goto keep_locked;
+
+ /* Page is dirty, try to write it out here */
+ switch (pageout(page, mapping, sc)) {
+ case PAGE_KEEP:
+ nr_congested++;
+ goto keep_locked;
+ case PAGE_ACTIVATE:
+ goto activate_locked;
+ case PAGE_SUCCESS:
+ if (PageWriteback(page))
+ goto keep_lumpy;
+ if (PageDirty(page))
+ goto keep;
+
+ /*
+ * A synchronous write - probably a ramdisk. Go
+ * ahead and try to reclaim the page.
+ */
+ if (!trylock_page(page))
+ goto keep;
+ if (PageDirty(page) || PageWriteback(page))
+ goto keep_locked;
+ mapping = page_mapping(page);
+ case PAGE_CLEAN:
+ ; /* try to free the page below */
+ }
+ }
+
+ /*
+ * If the page has buffers, try to free the buffer mappings
+ * associated with this page. If we succeed we try to free
+ * the page as well.
+ *
+ * We do this even if the page is PageDirty().
+ * try_to_release_page() does not perform I/O, but it is
+ * possible for a page to have PageDirty set, but it is actually
+ * clean (all its buffers are clean). This happens if the
+ * buffers were written out directly, with submit_bh(). ext3
+ * will do this, as well as the blockdev mapping.
+ * try_to_release_page() will discover that cleanness and will
+ * drop the buffers and mark the page clean - it can be freed.
+ *
+ * Rarely, pages can have buffers and no ->mapping. These are
+ * the pages which were not successfully invalidated in
+ * truncate_complete_page(). We try to drop those buffers here
+ * and if that worked, and the page is no longer mapped into
+ * process address space (page_count == 1) it can be freed.
+ * Otherwise, leave the page on the LRU so it is swappable.
+ */
+ if (page_has_private(page)) {
+ if (!try_to_release_page(page, sc->gfp_mask))
+ goto activate_locked;
+ if (!mapping && page_count(page) == 1) {
+ unlock_page(page);
+ if (put_page_testzero(page))
+ goto free_it;
+ else {
+ /*
+ * rare race with speculative reference.
+ * the speculative reference will free
+ * this page shortly, so we may
+ * increment nr_reclaimed here (and
+ * leave it off the LRU).
+ */
+ nr_reclaimed++;
+ continue;
+ }
+ }
+ }
+
+ if (!mapping || !__remove_mapping(mapping, page))
+ goto keep_locked;
+
+ /*
+ * At this point, we have no other references and there is
+ * no way to pick any more up (removed from LRU, removed
+ * from pagecache). Can use non-atomic bitops now (and
+ * we obviously don't have to worry about waking up a process
+ * waiting on the page lock, because there are no references.
+ */
+ __clear_page_locked(page);
+free_it:
+ nr_reclaimed++;
+
+ /*
+ * Is there need to periodically free_page_list? It would
+ * appear not as the counts should be low
+ */
+ list_add(&page->lru, &free_pages);
+ continue;
+
+cull_mlocked:
+ if (PageSwapCache(page))
+ try_to_free_swap(page);
+ unlock_page(page);
+ putback_lru_page(page);
+ reset_reclaim_mode(sc);
+ continue;
+
+activate_locked:
+ /* Not a candidate for swapping, so reclaim swap space. */
+ if (PageSwapCache(page) && vm_swap_full())
+ try_to_free_swap(page);
+ VM_BUG_ON(PageActive(page));
+ SetPageActive(page);
+ pgactivate++;
+keep_locked:
+ unlock_page(page);
+keep:
+ reset_reclaim_mode(sc);
+keep_lumpy:
+ list_add(&page->lru, &ret_pages);
+ VM_BUG_ON(PageLRU(page) || PageUnevictable(page));
+ }
+
+ /*
+ * Tag a zone as congested if all the dirty pages encountered were
+ * backed by a congested BDI. In this case, reclaimers should just
+ * back off and wait for congestion to clear because further reclaim
+ * will encounter the same problem
+ */
+ if (nr_dirty && nr_dirty == nr_congested && global_reclaim(sc))
+ zone_set_flag(mz->zone, ZONE_CONGESTED);
+
+ free_hot_cold_page_list(&free_pages, 1);
+
+ list_splice(&ret_pages, page_list);
+ count_vm_events(PGACTIVATE, pgactivate);
+ *ret_nr_dirty += nr_dirty;
+ *ret_nr_writeback += nr_writeback;
+ return nr_reclaimed;
+}
+
+/*
+ * Attempt to remove the specified page from its LRU. Only take this page
+ * if it is of the appropriate PageActive status. Pages which are being
+ * freed elsewhere are also ignored.
+ *
+ * page: page to consider
+ * mode: one of the LRU isolation modes defined above
+ *
+ * returns 0 on success, -ve errno on failure.
+ */
+int __isolate_lru_page(struct page *page, isolate_mode_t mode, int file)
+{
+ bool all_lru_mode;
+ int ret = -EINVAL;
+
+ /* Only take pages on the LRU. */
+ if (!PageLRU(page))
+ return ret;
+
+ all_lru_mode = (mode & (ISOLATE_ACTIVE|ISOLATE_INACTIVE)) ==
+ (ISOLATE_ACTIVE|ISOLATE_INACTIVE);
+
+ /*
+ * When checking the active state, we need to be sure we are
+ * dealing with comparible boolean values. Take the logical not
+ * of each.
+ */
+ if (!all_lru_mode && !PageActive(page) != !(mode & ISOLATE_ACTIVE))
+ return ret;
+
+ if (!all_lru_mode && !!page_is_file_cache(page) != file)
+ return ret;
+
+ /*
+ * When this function is being called for lumpy reclaim, we
+ * initially look into all LRU pages, active, inactive and
+ * unevictable; only give shrink_page_list evictable pages.
+ */
+ if (PageUnevictable(page))
+ return ret;
+
+ ret = -EBUSY;
+
+ /*
+ * To minimise LRU disruption, the caller can indicate that it only
+ * wants to isolate pages it will be able to operate on without
+ * blocking - clean pages for the most part.
+ *
+ * ISOLATE_CLEAN means that only clean pages should be isolated. This
+ * is used by reclaim when it is cannot write to backing storage
+ *
+ * ISOLATE_ASYNC_MIGRATE is used to indicate that it only wants to pages
+ * that it is possible to migrate without blocking
+ */
+ if (mode & (ISOLATE_CLEAN|ISOLATE_ASYNC_MIGRATE)) {
+ /* All the caller can do on PageWriteback is block */
+ if (PageWriteback(page))
+ return ret;
+
+ if (PageDirty(page)) {
+ struct address_space *mapping;
+
+ /* ISOLATE_CLEAN means only clean pages */
+ if (mode & ISOLATE_CLEAN)
+ return ret;
+
+ /*
+ * Only pages without mappings or that have a
+ * ->migratepage callback are possible to migrate
+ * without blocking
+ */
+ mapping = page_mapping(page);
+ if (mapping && !mapping->a_ops->migratepage)
+ return ret;
+ }
+ }
+
+ if ((mode & ISOLATE_UNMAPPED) && page_mapped(page))
+ return ret;
+
+ if (likely(get_page_unless_zero(page))) {
+ /*
+ * Be careful not to clear PageLRU until after we're
+ * sure the page is not being freed elsewhere -- the
+ * page release code relies on it.
+ */
+ ClearPageLRU(page);
+ ret = 0;
+ }
+
+ return ret;
+}
+
+/*
+ * zone->lru_lock is heavily contended. Some of the functions that
+ * shrink the lists perform better by taking out a batch of pages
+ * and working on them outside the LRU lock.
+ *
+ * For pagecache intensive workloads, this function is the hottest
+ * spot in the kernel (apart from copy_*_user functions).
+ *
+ * Appropriate locks must be held before calling this function.
+ *
+ * @nr_to_scan: The number of pages to look through on the list.
+ * @mz: The mem_cgroup_zone to pull pages from.
+ * @dst: The temp list to put pages on to.
+ * @nr_scanned: The number of pages that were scanned.
+ * @sc: The scan_control struct for this reclaim session
+ * @mode: One of the LRU isolation modes
+ * @active: True [1] if isolating active pages
+ * @file: True [1] if isolating file [!anon] pages
+ *
+ * returns how many pages were moved onto *@dst.
+ */
+static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
+ struct mem_cgroup_zone *mz, struct list_head *dst,
+ unsigned long *nr_scanned, struct scan_control *sc,
+ isolate_mode_t mode, int active, int file)
+{
+ struct lruvec *lruvec;
+ struct list_head *src;
+ unsigned long nr_taken = 0;
+ unsigned long nr_lumpy_taken = 0;
+ unsigned long nr_lumpy_dirty = 0;
+ unsigned long nr_lumpy_failed = 0;
+ unsigned long scan;
+ int lru = LRU_BASE;
+
+ lruvec = mem_cgroup_zone_lruvec(mz->zone, mz->mem_cgroup);
+ if (active)
+ lru += LRU_ACTIVE;
+ if (file)
+ lru += LRU_FILE;
+ src = &lruvec->lists[lru];
+
+ for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
+ struct page *page;
+ unsigned long pfn;
+ unsigned long end_pfn;
+ unsigned long page_pfn;
+ int zone_id;
+
+ page = lru_to_page(src);
+ prefetchw_prev_lru_page(page, src, flags);
+
+ VM_BUG_ON(!PageLRU(page));
+
+ switch (__isolate_lru_page(page, mode, file)) {
+ case 0:
+ mem_cgroup_lru_del(page);
+ list_move(&page->lru, dst);
+ nr_taken += hpage_nr_pages(page);
+ break;
+
+ case -EBUSY:
+ /* else it is being freed elsewhere */
+ list_move(&page->lru, src);
+ continue;
+
+ default:
+ BUG();
+ }
+
+ if (!sc->order || !(sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM))
+ continue;
+
+ /*
+ * Attempt to take all pages in the order aligned region
+ * surrounding the tag page. Only take those pages of
+ * the same active state as that tag page. We may safely
+ * round the target page pfn down to the requested order
+ * as the mem_map is guaranteed valid out to MAX_ORDER,
+ * where that page is in a different zone we will detect
+ * it from its zone id and abort this block scan.
+ */
+ zone_id = page_zone_id(page);
+ page_pfn = page_to_pfn(page);
+ pfn = page_pfn & ~((1 << sc->order) - 1);
+ end_pfn = pfn + (1 << sc->order);
+ for (; pfn < end_pfn; pfn++) {
+ struct page *cursor_page;
+
+ /* The target page is in the block, ignore it. */
+ if (unlikely(pfn == page_pfn))
+ continue;
+
+ /* Avoid holes within the zone. */
+ if (unlikely(!pfn_valid_within(pfn)))
+ break;
+
+ cursor_page = pfn_to_page(pfn);
+
+ /* Check that we have not crossed a zone boundary. */
+ if (unlikely(page_zone_id(cursor_page) != zone_id))
+ break;
+
+ /*
+ * If we don't have enough swap space, reclaiming of
+ * anon page which don't already have a swap slot is
+ * pointless.
+ */
+ if (nr_swap_pages <= 0 && PageSwapBacked(cursor_page) &&
+ !PageSwapCache(cursor_page))
+ break;
+
+ if (__isolate_lru_page(cursor_page, mode, file) == 0) {
+ unsigned int isolated_pages;
+
+ mem_cgroup_lru_del(cursor_page);
+ list_move(&cursor_page->lru, dst);
+ isolated_pages = hpage_nr_pages(cursor_page);
+ nr_taken += isolated_pages;
+ nr_lumpy_taken += isolated_pages;
+ if (PageDirty(cursor_page))
+ nr_lumpy_dirty += isolated_pages;
+ scan++;
+ pfn += isolated_pages - 1;
+ } else {
+ /*
+ * Check if the page is freed already.
+ *
+ * We can't use page_count() as that
+ * requires compound_head and we don't
+ * have a pin on the page here. If a
+ * page is tail, we may or may not
+ * have isolated the head, so assume
+ * it's not free, it'd be tricky to
+ * track the head status without a
+ * page pin.
+ */
+ if (!PageTail(cursor_page) &&
+ !atomic_read(&cursor_page->_count))
+ continue;
+ break;
+ }
+ }
+
+ /* If we break out of the loop above, lumpy reclaim failed */
+ if (pfn < end_pfn)
+ nr_lumpy_failed++;
+ }
+
+ *nr_scanned = scan;
+
+ trace_mm_vmscan_lru_isolate(sc->order,
+ nr_to_scan, scan,
+ nr_taken,
+ nr_lumpy_taken, nr_lumpy_dirty, nr_lumpy_failed,
+ mode, file);
+ return nr_taken;
+}
+
+/**
+ * isolate_lru_page - tries to isolate a page from its LRU list
+ * @page: page to isolate from its LRU list
+ *
+ * Isolates a @page from an LRU list, clears PageLRU and adjusts the
+ * vmstat statistic corresponding to whatever LRU list the page was on.
+ *
+ * Returns 0 if the page was removed from an LRU list.
+ * Returns -EBUSY if the page was not on an LRU list.
+ *
+ * The returned page will have PageLRU() cleared. If it was found on
+ * the active list, it will have PageActive set. If it was found on
+ * the unevictable list, it will have the PageUnevictable bit set. That flag
+ * may need to be cleared by the caller before letting the page go.
+ *
+ * The vmstat statistic corresponding to the list on which the page was
+ * found will be decremented.
+ *
+ * Restrictions:
+ * (1) Must be called with an elevated refcount on the page. This is a
+ * fundamentnal difference from isolate_lru_pages (which is called
+ * without a stable reference).
+ * (2) the lru_lock must not be held.
+ * (3) interrupts must be enabled.
+ */
+int isolate_lru_page(struct page *page)
+{
+ int ret = -EBUSY;
+
+ VM_BUG_ON(!page_count(page));
+
+ if (PageLRU(page)) {
+ struct zone *zone = page_zone(page);
+
+ spin_lock_irq(&zone->lru_lock);
+ if (PageLRU(page)) {
+ int lru = page_lru(page);
+ ret = 0;
+ get_page(page);
+ ClearPageLRU(page);
+
+ del_page_from_lru_list(zone, page, lru);
+ }
+ spin_unlock_irq(&zone->lru_lock);
+ }
+ return ret;
+}
+
+/*
+ * Are there way too many processes in the direct reclaim path already?
+ */
+static int too_many_isolated(struct zone *zone, int file,
+ struct scan_control *sc)
+{
+ unsigned long inactive, isolated;
+
+ if (current_is_kswapd())
+ return 0;
+
+ if (!global_reclaim(sc))
+ return 0;
+
+ if (file) {
+ inactive = zone_page_state(zone, NR_INACTIVE_FILE);
+ isolated = zone_page_state(zone, NR_ISOLATED_FILE);
+ } else {
+ inactive = zone_page_state(zone, NR_INACTIVE_ANON);
+ isolated = zone_page_state(zone, NR_ISOLATED_ANON);
+ }
+
+ return isolated > inactive;
+}
+
+static noinline_for_stack void
+putback_inactive_pages(struct mem_cgroup_zone *mz,
+ struct list_head *page_list)
+{
+ struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(mz);
+ struct zone *zone = mz->zone;
+ LIST_HEAD(pages_to_free);
+
+ /*
+ * Put back any unfreeable pages.
+ */
+ while (!list_empty(page_list)) {
+ struct page *page = lru_to_page(page_list);
+ int lru;
+
+ VM_BUG_ON(PageLRU(page));
+ list_del(&page->lru);
+ if (unlikely(!page_evictable(page, NULL))) {
+ spin_unlock_irq(&zone->lru_lock);
+ putback_lru_page(page);
+ spin_lock_irq(&zone->lru_lock);
+ continue;
+ }
+ SetPageLRU(page);
+ lru = page_lru(page);
+ add_page_to_lru_list(zone, page, lru);
+ if (is_active_lru(lru)) {
+ int file = is_file_lru(lru);
+ int numpages = hpage_nr_pages(page);
+ reclaim_stat->recent_rotated[file] += numpages;
+ }
+ if (put_page_testzero(page)) {
+ __ClearPageLRU(page);
+ __ClearPageActive(page);
+ del_page_from_lru_list(zone, page, lru);
+
+ if (unlikely(PageCompound(page))) {
+ spin_unlock_irq(&zone->lru_lock);
+ (*get_compound_page_dtor(page))(page);
+ spin_lock_irq(&zone->lru_lock);
+ } else
+ list_add(&page->lru, &pages_to_free);
+ }
+ }
+
+ /*
+ * To save our caller's stack, now use input list for pages to free.
+ */
+ list_splice(&pages_to_free, page_list);
+}
+
+static noinline_for_stack void
+update_isolated_counts(struct mem_cgroup_zone *mz,
+ struct list_head *page_list,
+ unsigned long *nr_anon,
+ unsigned long *nr_file)
+{
+ struct zone *zone = mz->zone;
+ unsigned int count[NR_LRU_LISTS] = { 0, };
+ unsigned long nr_active = 0;
+ struct page *page;
+ int lru;
+
+ /*
+ * Count pages and clear active flags
+ */
+ list_for_each_entry(page, page_list, lru) {
+ int numpages = hpage_nr_pages(page);
+ lru = page_lru_base_type(page);
+ if (PageActive(page)) {
+ lru += LRU_ACTIVE;
+ ClearPageActive(page);
+ nr_active += numpages;
+ }
+ count[lru] += numpages;
+ }
+
+ preempt_disable();
+ __count_vm_events(PGDEACTIVATE, nr_active);
+
+ __mod_zone_page_state(zone, NR_ACTIVE_FILE,
+ -count[LRU_ACTIVE_FILE]);
+ __mod_zone_page_state(zone, NR_INACTIVE_FILE,
+ -count[LRU_INACTIVE_FILE]);
+ __mod_zone_page_state(zone, NR_ACTIVE_ANON,
+ -count[LRU_ACTIVE_ANON]);
+ __mod_zone_page_state(zone, NR_INACTIVE_ANON,
+ -count[LRU_INACTIVE_ANON]);
+
+ *nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON];
+ *nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE];
+
+ __mod_zone_page_state(zone, NR_ISOLATED_ANON, *nr_anon);
+ __mod_zone_page_state(zone, NR_ISOLATED_FILE, *nr_file);
+ preempt_enable();
+}
+
+/*
+ * Returns true if a direct reclaim should wait on pages under writeback.
+ *
+ * If we are direct reclaiming for contiguous pages and we do not reclaim
+ * everything in the list, try again and wait for writeback IO to complete.
+ * This will stall high-order allocations noticeably. Only do that when really
+ * need to free the pages under high memory pressure.
+ */
+static inline bool should_reclaim_stall(unsigned long nr_taken,
+ unsigned long nr_freed,
+ int priority,
+ struct scan_control *sc)
+{
+ int lumpy_stall_priority;
+
+ /* kswapd should not stall on sync IO */
+ if (current_is_kswapd())
+ return false;
+
+ /* Only stall on lumpy reclaim */
+ if (sc->reclaim_mode & RECLAIM_MODE_SINGLE)
+ return false;
+
+ /* If we have reclaimed everything on the isolated list, no stall */
+ if (nr_freed == nr_taken)
+ return false;
+
+ /*
+ * For high-order allocations, there are two stall thresholds.
+ * High-cost allocations stall immediately where as lower
+ * order allocations such as stacks require the scanning
+ * priority to be much higher before stalling.
+ */
+ if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
+ lumpy_stall_priority = DEF_PRIORITY;
+ else
+ lumpy_stall_priority = DEF_PRIORITY / 3;
+
+ return priority <= lumpy_stall_priority;
+}
+
+/*
+ * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
+ * of reclaimed pages
+ */
+static noinline_for_stack unsigned long
+shrink_inactive_list(unsigned long nr_to_scan, struct mem_cgroup_zone *mz,
+ struct scan_control *sc, int priority, int file)
+{
+ LIST_HEAD(page_list);
+ unsigned long nr_scanned;
+ unsigned long nr_reclaimed = 0;
+ unsigned long nr_taken;
+ unsigned long nr_anon;
+ unsigned long nr_file;
+ unsigned long nr_dirty = 0;
+ unsigned long nr_writeback = 0;
+ isolate_mode_t isolate_mode = ISOLATE_INACTIVE;
+ struct zone *zone = mz->zone;
+ struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(mz);
+
+ while (unlikely(too_many_isolated(zone, file, sc))) {
+ congestion_wait(BLK_RW_ASYNC, HZ/10);
+
+ /* We are about to die and free our memory. Return now. */
+ if (fatal_signal_pending(current))
+ return SWAP_CLUSTER_MAX;
+ }
+
+ set_reclaim_mode(priority, sc, false);
+ if (sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM)
+ isolate_mode |= ISOLATE_ACTIVE;
+
+ lru_add_drain();
+
+ if (!sc->may_unmap)
+ isolate_mode |= ISOLATE_UNMAPPED;
+ if (!sc->may_writepage)
+ isolate_mode |= ISOLATE_CLEAN;
+
+ spin_lock_irq(&zone->lru_lock);
+
+ nr_taken = isolate_lru_pages(nr_to_scan, mz, &page_list, &nr_scanned,
+ sc, isolate_mode, 0, file);
+ if (global_reclaim(sc)) {
+ zone->pages_scanned += nr_scanned;
+ if (current_is_kswapd())
+ __count_zone_vm_events(PGSCAN_KSWAPD, zone,
+ nr_scanned);
+ else
+ __count_zone_vm_events(PGSCAN_DIRECT, zone,
+ nr_scanned);
+ }
+ spin_unlock_irq(&zone->lru_lock);
+
+ if (nr_taken == 0)
+ return 0;
+
+ update_isolated_counts(mz, &page_list, &nr_anon, &nr_file);
+
+ nr_reclaimed = shrink_page_list(&page_list, mz, sc, priority,
+ &nr_dirty, &nr_writeback);
+
+ /* Check if we should syncronously wait for writeback */
+ if (should_reclaim_stall(nr_taken, nr_reclaimed, priority, sc)) {
+ set_reclaim_mode(priority, sc, true);
+ nr_reclaimed += shrink_page_list(&page_list, mz, sc,
+ priority, &nr_dirty, &nr_writeback);
+ }
+
+ spin_lock_irq(&zone->lru_lock);
+
+ reclaim_stat->recent_scanned[0] += nr_anon;
+ reclaim_stat->recent_scanned[1] += nr_file;
+
+ if (global_reclaim(sc)) {
+ if (current_is_kswapd())
+ __count_zone_vm_events(PGSTEAL_KSWAPD, zone,
+ nr_reclaimed);
+ else
+ __count_zone_vm_events(PGSTEAL_DIRECT, zone,
+ nr_reclaimed);
+ }
+
+ putback_inactive_pages(mz, &page_list);
+
+ __mod_zone_page_state(zone, NR_ISOLATED_ANON, -nr_anon);
+ __mod_zone_page_state(zone, NR_ISOLATED_FILE, -nr_file);
+
+ spin_unlock_irq(&zone->lru_lock);
+
+ free_hot_cold_page_list(&page_list, 1);
+
+ /*
+ * If reclaim is isolating dirty pages under writeback, it implies
+ * that the long-lived page allocation rate is exceeding the page
+ * laundering rate. Either the global limits are not being effective
+ * at throttling processes due to the page distribution throughout
+ * zones or there is heavy usage of a slow backing device. The
+ * only option is to throttle from reclaim context which is not ideal
+ * as there is no guarantee the dirtying process is throttled in the
+ * same way balance_dirty_pages() manages.
+ *
+ * This scales the number of dirty pages that must be under writeback
+ * before throttling depending on priority. It is a simple backoff
+ * function that has the most effect in the range DEF_PRIORITY to
+ * DEF_PRIORITY-2 which is the priority reclaim is considered to be
+ * in trouble and reclaim is considered to be in trouble.
+ *
+ * DEF_PRIORITY 100% isolated pages must be PageWriteback to throttle
+ * DEF_PRIORITY-1 50% must be PageWriteback
+ * DEF_PRIORITY-2 25% must be PageWriteback, kswapd in trouble
+ * ...
+ * DEF_PRIORITY-6 For SWAP_CLUSTER_MAX isolated pages, throttle if any
+ * isolated page is PageWriteback
+ */
+ if (nr_writeback && nr_writeback >= (nr_taken >> (DEF_PRIORITY-priority)))
+ wait_iff_congested(zone, BLK_RW_ASYNC, HZ/10);
+
+ trace_mm_vmscan_lru_shrink_inactive(zone->zone_pgdat->node_id,
+ zone_idx(zone),
+ nr_scanned, nr_reclaimed,
+ priority,
+ trace_shrink_flags(file, sc->reclaim_mode));
+ return nr_reclaimed;
+}
+
+/*
+ * This moves pages from the active list to the inactive list.
+ *
+ * We move them the other way if the page is referenced by one or more
+ * processes, from rmap.
+ *
+ * If the pages are mostly unmapped, the processing is fast and it is
+ * appropriate to hold zone->lru_lock across the whole operation. But if
+ * the pages are mapped, the processing is slow (page_referenced()) so we
+ * should drop zone->lru_lock around each page. It's impossible to balance
+ * this, so instead we remove the pages from the LRU while processing them.
+ * It is safe to rely on PG_active against the non-LRU pages in here because
+ * nobody will play with that bit on a non-LRU page.
+ *
+ * The downside is that we have to touch page->_count against each page.
+ * But we had to alter page->flags anyway.
+ */
+
+static void move_active_pages_to_lru(struct zone *zone,
+ struct list_head *list,
+ struct list_head *pages_to_free,
+ enum lru_list lru)
+{
+ unsigned long pgmoved = 0;
+ struct page *page;
+
+ while (!list_empty(list)) {
+ struct lruvec *lruvec;
+
+ page = lru_to_page(list);
+
+ VM_BUG_ON(PageLRU(page));
+ SetPageLRU(page);
+
+ lruvec = mem_cgroup_lru_add_list(zone, page, lru);
+ list_move(&page->lru, &lruvec->lists[lru]);
+ pgmoved += hpage_nr_pages(page);
+
+ if (put_page_testzero(page)) {
+ __ClearPageLRU(page);
+ __ClearPageActive(page);
+ del_page_from_lru_list(zone, page, lru);
+
+ if (unlikely(PageCompound(page))) {
+ spin_unlock_irq(&zone->lru_lock);
+ (*get_compound_page_dtor(page))(page);
+ spin_lock_irq(&zone->lru_lock);
+ } else
+ list_add(&page->lru, pages_to_free);
+ }
+ }
+ __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved);
+ if (!is_active_lru(lru))
+ __count_vm_events(PGDEACTIVATE, pgmoved);
+}
+
+static void shrink_active_list(unsigned long nr_to_scan,
+ struct mem_cgroup_zone *mz,
+ struct scan_control *sc,
+ int priority, int file)
+{
+ unsigned long nr_taken;
+ unsigned long nr_scanned;
+ unsigned long vm_flags;
+ LIST_HEAD(l_hold); /* The pages which were snipped off */
+ LIST_HEAD(l_active);
+ LIST_HEAD(l_inactive);
+ struct page *page;
+ struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(mz);
+ unsigned long nr_rotated = 0;
+ isolate_mode_t isolate_mode = ISOLATE_ACTIVE;
+ struct zone *zone = mz->zone;
+
+ lru_add_drain();
+
+ reset_reclaim_mode(sc);
+
+ if (!sc->may_unmap)
+ isolate_mode |= ISOLATE_UNMAPPED;
+ if (!sc->may_writepage)
+ isolate_mode |= ISOLATE_CLEAN;
+
+ spin_lock_irq(&zone->lru_lock);
+
+ nr_taken = isolate_lru_pages(nr_to_scan, mz, &l_hold, &nr_scanned, sc,
+ isolate_mode, 1, file);
+ if (global_reclaim(sc))
+ zone->pages_scanned += nr_scanned;
+
+ reclaim_stat->recent_scanned[file] += nr_taken;
+
+ __count_zone_vm_events(PGREFILL, zone, nr_scanned);
+ if (file)
+ __mod_zone_page_state(zone, NR_ACTIVE_FILE, -nr_taken);
+ else
+ __mod_zone_page_state(zone, NR_ACTIVE_ANON, -nr_taken);
+ __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken);
+ spin_unlock_irq(&zone->lru_lock);
+
+ while (!list_empty(&l_hold)) {
+ cond_resched();
+ page = lru_to_page(&l_hold);
+ list_del(&page->lru);
+
+ if (unlikely(!page_evictable(page, NULL))) {
+ putback_lru_page(page);
+ continue;
+ }
+
+ if (unlikely(buffer_heads_over_limit)) {
+ if (page_has_private(page) && trylock_page(page)) {
+ if (page_has_private(page))
+ try_to_release_page(page, 0);
+ unlock_page(page);
+ }
+ }
+
+ if (page_referenced(page, 0, mz->mem_cgroup, &vm_flags)) {
+ nr_rotated += hpage_nr_pages(page);
+ /*
+ * Identify referenced, file-backed active pages and
+ * give them one more trip around the active list. So
+ * that executable code get better chances to stay in
+ * memory under moderate memory pressure. Anon pages
+ * are not likely to be evicted by use-once streaming
+ * IO, plus JVM can create lots of anon VM_EXEC pages,
+ * so we ignore them here.
+ */
+ if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) {
+ list_add(&page->lru, &l_active);
+ continue;
+ }
+ }
+
+ ClearPageActive(page); /* we are de-activating */
+ list_add(&page->lru, &l_inactive);
+ }
+
+ /*
+ * Move pages back to the lru list.
+ */
+ spin_lock_irq(&zone->lru_lock);
+ /*
+ * Count referenced pages from currently used mappings as rotated,
+ * even though only some of them are actually re-activated. This
+ * helps balance scan pressure between file and anonymous pages in
+ * get_scan_ratio.
+ */
+ reclaim_stat->recent_rotated[file] += nr_rotated;
+
+ move_active_pages_to_lru(zone, &l_active, &l_hold,
+ LRU_ACTIVE + file * LRU_FILE);
+ move_active_pages_to_lru(zone, &l_inactive, &l_hold,
+ LRU_BASE + file * LRU_FILE);
+ __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken);
+ spin_unlock_irq(&zone->lru_lock);
+
+ free_hot_cold_page_list(&l_hold, 1);
+}
+
+#ifdef CONFIG_SWAP
+static int inactive_anon_is_low_global(struct zone *zone)
+{
+ unsigned long active, inactive;
+
+ active = zone_page_state(zone, NR_ACTIVE_ANON);
+ inactive = zone_page_state(zone, NR_INACTIVE_ANON);
+
+ if (inactive * zone->inactive_ratio < active)
+ return 1;
+
+ return 0;
+}
+
+/**
+ * inactive_anon_is_low - check if anonymous pages need to be deactivated
+ * @zone: zone to check
+ * @sc: scan control of this context
+ *
+ * Returns true if the zone does not have enough inactive anon pages,
+ * meaning some active anon pages need to be deactivated.
+ */
+static int inactive_anon_is_low(struct mem_cgroup_zone *mz)
+{
+ /*
+ * If we don't have swap space, anonymous page deactivation
+ * is pointless.
+ */
+ if (!total_swap_pages)
+ return 0;
+
+ if (!scanning_global_lru(mz))
+ return mem_cgroup_inactive_anon_is_low(mz->mem_cgroup,
+ mz->zone);
+
+ return inactive_anon_is_low_global(mz->zone);
+}
+#else
+static inline int inactive_anon_is_low(struct mem_cgroup_zone *mz)
+{
+ return 0;
+}
+#endif
+
+static int inactive_file_is_low_global(struct zone *zone)
+{
+ unsigned long active, inactive;
+
+ active = zone_page_state(zone, NR_ACTIVE_FILE);
+ inactive = zone_page_state(zone, NR_INACTIVE_FILE);
+
+ return (active > inactive);
+}
+
+/**
+ * inactive_file_is_low - check if file pages need to be deactivated
+ * @mz: memory cgroup and zone to check
+ *
+ * When the system is doing streaming IO, memory pressure here
+ * ensures that active file pages get deactivated, until more
+ * than half of the file pages are on the inactive list.
+ *
+ * Once we get to that situation, protect the system's working
+ * set from being evicted by disabling active file page aging.
+ *
+ * This uses a different ratio than the anonymous pages, because
+ * the page cache uses a use-once replacement algorithm.
+ */
+static int inactive_file_is_low(struct mem_cgroup_zone *mz)
+{
+ if (!scanning_global_lru(mz))
+ return mem_cgroup_inactive_file_is_low(mz->mem_cgroup,
+ mz->zone);
+
+ return inactive_file_is_low_global(mz->zone);
+}
+
+static int inactive_list_is_low(struct mem_cgroup_zone *mz, int file)
+{
+ if (file)
+ return inactive_file_is_low(mz);
+ else
+ return inactive_anon_is_low(mz);
+}
+
+static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
+ struct mem_cgroup_zone *mz,
+ struct scan_control *sc, int priority)
+{
+ int file = is_file_lru(lru);
+
+ if (is_active_lru(lru)) {
+ if (inactive_list_is_low(mz, file))
+ shrink_active_list(nr_to_scan, mz, sc, priority, file);
+ return 0;
+ }
+
+ return shrink_inactive_list(nr_to_scan, mz, sc, priority, file);
+}
+
+static int vmscan_swappiness(struct mem_cgroup_zone *mz,
+ struct scan_control *sc)
+{
+ if (global_reclaim(sc))
+ return vm_swappiness;
+ return mem_cgroup_swappiness(mz->mem_cgroup);
+}
+
+/*
+ * Determine how aggressively the anon and file LRU lists should be
+ * scanned. The relative value of each set of LRU lists is determined
+ * by looking at the fraction of the pages scanned we did rotate back
+ * onto the active list instead of evict.
+ *
+ * nr[0] = anon pages to scan; nr[1] = file pages to scan
+ */
+static void get_scan_count(struct mem_cgroup_zone *mz, struct scan_control *sc,
+ unsigned long *nr, int priority)
+{
+ unsigned long anon, file, free;
+ unsigned long anon_prio, file_prio;
+ unsigned long ap, fp;
+ struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(mz);
+ u64 fraction[2], denominator;
+ enum lru_list lru;
+ int noswap = 0;
+ bool force_scan = false;
+
+ /*
+ * If the zone or memcg is small, nr[l] can be 0. This
+ * results in no scanning on this priority and a potential
+ * priority drop. Global direct reclaim can go to the next
+ * zone and tends to have no problems. Global kswapd is for
+ * zone balancing and it needs to scan a minimum amount. When
+ * reclaiming for a memcg, a priority drop can cause high
+ * latencies, so it's better to scan a minimum amount there as
+ * well.
+ */
+ if (current_is_kswapd() && mz->zone->all_unreclaimable)
+ force_scan = true;
+ if (!global_reclaim(sc))
+ force_scan = true;
+
+ /* If we have no swap space, do not bother scanning anon pages. */
+ if (!sc->may_swap || (nr_swap_pages <= 0)) {
+ noswap = 1;
+ fraction[0] = 0;
+ fraction[1] = 1;
+ denominator = 1;
+ goto out;
+ }
+
+ anon = zone_nr_lru_pages(mz, LRU_ACTIVE_ANON) +
+ zone_nr_lru_pages(mz, LRU_INACTIVE_ANON);
+ file = zone_nr_lru_pages(mz, LRU_ACTIVE_FILE) +
+ zone_nr_lru_pages(mz, LRU_INACTIVE_FILE);
+
+ if (global_reclaim(sc)) {
+ free = zone_page_state(mz->zone, NR_FREE_PAGES);
+ /* If we have very few page cache pages,
+ force-scan anon pages. */
+ if (unlikely(file + free <= high_wmark_pages(mz->zone))) {
+ fraction[0] = 1;
+ fraction[1] = 0;
+ denominator = 1;
+ goto out;
+ }
+ }
+
+ /*
+ * With swappiness at 100, anonymous and file have the same priority.
+ * This scanning priority is essentially the inverse of IO cost.
+ */
+ anon_prio = vmscan_swappiness(mz, sc);
+ file_prio = 200 - vmscan_swappiness(mz, sc);
+
+ /*
+ * OK, so we have swap space and a fair amount of page cache
+ * pages. We use the recently rotated / recently scanned
+ * ratios to determine how valuable each cache is.
+ *
+ * Because workloads change over time (and to avoid overflow)
+ * we keep these statistics as a floating average, which ends
+ * up weighing recent references more than old ones.
+ *
+ * anon in [0], file in [1]
+ */
+ spin_lock_irq(&mz->zone->lru_lock);
+ if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) {
+ reclaim_stat->recent_scanned[0] /= 2;
+ reclaim_stat->recent_rotated[0] /= 2;
+ }
+
+ if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) {
+ reclaim_stat->recent_scanned[1] /= 2;
+ reclaim_stat->recent_rotated[1] /= 2;
+ }
+
+ /*
+ * The amount of pressure on anon vs file pages is inversely
+ * proportional to the fraction of recently scanned pages on
+ * each list that were recently referenced and in active use.
+ */
+ ap = anon_prio * (reclaim_stat->recent_scanned[0] + 1);
+ ap /= reclaim_stat->recent_rotated[0] + 1;
+
+ fp = file_prio * (reclaim_stat->recent_scanned[1] + 1);
+ fp /= reclaim_stat->recent_rotated[1] + 1;
+ spin_unlock_irq(&mz->zone->lru_lock);
+
+ fraction[0] = ap;
+ fraction[1] = fp;
+ denominator = ap + fp + 1;
+out:
+ for_each_evictable_lru(lru) {
+ int file = is_file_lru(lru);
+ unsigned long scan;
+
+ scan = zone_nr_lru_pages(mz, lru);
+ if (priority || noswap || !vmscan_swappiness(mz, sc)) {
+ scan >>= priority;
+ if (!scan && force_scan)
+ scan = SWAP_CLUSTER_MAX;
+ scan = div64_u64(scan * fraction[file], denominator);
+ }
+ nr[lru] = scan;
+ }
+}
+
+/*
+ * Reclaim/compaction depends on a number of pages being freed. To avoid
+ * disruption to the system, a small number of order-0 pages continue to be
+ * rotated and reclaimed in the normal fashion. However, by the time we get
+ * back to the allocator and call try_to_compact_zone(), we ensure that
+ * there are enough free pages for it to be likely successful
+ */
+static inline bool should_continue_reclaim(struct mem_cgroup_zone *mz,
+ unsigned long nr_reclaimed,
+ unsigned long nr_scanned,
+ struct scan_control *sc)
+{
+ unsigned long pages_for_compaction;
+ unsigned long inactive_lru_pages;
+
+ /* If not in reclaim/compaction mode, stop */
+ if (!(sc->reclaim_mode & RECLAIM_MODE_COMPACTION))
+ return false;
+
+ /* Consider stopping depending on scan and reclaim activity */
+ if (sc->gfp_mask & __GFP_REPEAT) {
+ /*
+ * For __GFP_REPEAT allocations, stop reclaiming if the
+ * full LRU list has been scanned and we are still failing
+ * to reclaim pages. This full LRU scan is potentially
+ * expensive but a __GFP_REPEAT caller really wants to succeed
+ */
+ if (!nr_reclaimed && !nr_scanned)
+ return false;
+ } else {
+ /*
+ * For non-__GFP_REPEAT allocations which can presumably
+ * fail without consequence, stop if we failed to reclaim
+ * any pages from the last SWAP_CLUSTER_MAX number of
+ * pages that were scanned. This will return to the
+ * caller faster at the risk reclaim/compaction and
+ * the resulting allocation attempt fails
+ */
+ if (!nr_reclaimed)
+ return false;
+ }
+
+ /*
+ * If we have not reclaimed enough pages for compaction and the
+ * inactive lists are large enough, continue reclaiming
+ */
+ pages_for_compaction = (2UL << sc->order);
+ inactive_lru_pages = zone_nr_lru_pages(mz, LRU_INACTIVE_FILE);
+ if (nr_swap_pages > 0)
+ inactive_lru_pages += zone_nr_lru_pages(mz, LRU_INACTIVE_ANON);
+ if (sc->nr_reclaimed < pages_for_compaction &&
+ inactive_lru_pages > pages_for_compaction)
+ return true;
+
+ /* If compaction would go ahead or the allocation would succeed, stop */
+ switch (compaction_suitable(mz->zone, sc->order)) {
+ case COMPACT_PARTIAL:
+ case COMPACT_CONTINUE:
+ return false;
+ default:
+ return true;
+ }
+}
+
+/*
+ * This is a basic per-zone page freer. Used by both kswapd and direct reclaim.
+ */
+static void shrink_mem_cgroup_zone(int priority, struct mem_cgroup_zone *mz,
+ struct scan_control *sc)
+{
+ unsigned long nr[NR_LRU_LISTS];
+ unsigned long nr_to_scan;
+ enum lru_list lru;
+ unsigned long nr_reclaimed, nr_scanned;
+ unsigned long nr_to_reclaim = sc->nr_to_reclaim;
+ struct blk_plug plug;
+
+restart:
+ nr_reclaimed = 0;
+ nr_scanned = sc->nr_scanned;
+ get_scan_count(mz, sc, nr, priority);
+
+ blk_start_plug(&plug);
+ while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
+ nr[LRU_INACTIVE_FILE]) {
+ for_each_evictable_lru(lru) {
+ if (nr[lru]) {
+ nr_to_scan = min_t(unsigned long,
+ nr[lru], SWAP_CLUSTER_MAX);
+ nr[lru] -= nr_to_scan;
+
+ nr_reclaimed += shrink_list(lru, nr_to_scan,
+ mz, sc, priority);
+ }
+ }
+ /*
+ * On large memory systems, scan >> priority can become
+ * really large. This is fine for the starting priority;
+ * we want to put equal scanning pressure on each zone.
+ * However, if the VM has a harder time of freeing pages,
+ * with multiple processes reclaiming pages, the total
+ * freeing target can get unreasonably large.
+ */
+ if (nr_reclaimed >= nr_to_reclaim && priority < DEF_PRIORITY)
+ break;
+ }
+ blk_finish_plug(&plug);
+ sc->nr_reclaimed += nr_reclaimed;
+
+ /*
+ * Even if we did not try to evict anon pages at all, we want to
+ * rebalance the anon lru active/inactive ratio.
+ */
+ if (inactive_anon_is_low(mz))
+ shrink_active_list(SWAP_CLUSTER_MAX, mz, sc, priority, 0);
+
+ /* reclaim/compaction might need reclaim to continue */
+ if (should_continue_reclaim(mz, nr_reclaimed,
+ sc->nr_scanned - nr_scanned, sc))
+ goto restart;
+
+ throttle_vm_writeout(sc->gfp_mask);
+}
+
+static void shrink_zone(int priority, struct zone *zone,
+ struct scan_control *sc)
+{
+ struct mem_cgroup *root = sc->target_mem_cgroup;
+ struct mem_cgroup_reclaim_cookie reclaim = {
+ .zone = zone,
+ .priority = priority,
+ };
+ struct mem_cgroup *memcg;
+
+#ifdef CONFIG_LIMIT_PAGE_CACHE
+ /*
+ * If the page cache is too big then focus on page cache
+ * and ignore anonymous pages
+ */
+ if (sc->may_swap && zone_page_state(zone, NR_FILE_PAGES)
+ > zone->max_pagecache_pages)
+ sc->may_swap = 0;
+#endif
+
+ memcg = mem_cgroup_iter(root, NULL, &reclaim);
+ do {
+ struct mem_cgroup_zone mz = {
+ .mem_cgroup = memcg,
+ .zone = zone,
+ };
+
+ shrink_mem_cgroup_zone(priority, &mz, sc);
+ /*
+ * Limit reclaim has historically picked one memcg and
+ * scanned it with decreasing priority levels until
+ * nr_to_reclaim had been reclaimed. This priority
+ * cycle is thus over after a single memcg.
+ *
+ * Direct reclaim and kswapd, on the other hand, have
+ * to scan all memory cgroups to fulfill the overall
+ * scan target for the zone.
+ */
+ if (!global_reclaim(sc)) {
+ mem_cgroup_iter_break(root, memcg);
+ break;
+ }
+ memcg = mem_cgroup_iter(root, memcg, &reclaim);
+ } while (memcg);
+}
+
+/* Returns true if compaction should go ahead for a high-order request */
+static inline bool compaction_ready(struct zone *zone, struct scan_control *sc)
+{
+ unsigned long balance_gap, watermark;
+ bool watermark_ok;
+
+ /* Do not consider compaction for orders reclaim is meant to satisfy */
+ if (sc->order <= PAGE_ALLOC_COSTLY_ORDER)
+ return false;
+
+ /*
+ * Compaction takes time to run and there are potentially other
+ * callers using the pages just freed. Continue reclaiming until
+ * there is a buffer of free pages available to give compaction
+ * a reasonable chance of completing and allocating the page
+ */
+ balance_gap = min(low_wmark_pages(zone),
+ (zone->present_pages + KSWAPD_ZONE_BALANCE_GAP_RATIO-1) /
+ KSWAPD_ZONE_BALANCE_GAP_RATIO);
+ watermark = high_wmark_pages(zone) + balance_gap + (2UL << sc->order);
+ watermark_ok = zone_watermark_ok_safe(zone, 0, watermark, 0, 0);
+
+ /*
+ * If compaction is deferred, reclaim up to a point where
+ * compaction will have a chance of success when re-enabled
+ */
+ if (compaction_deferred(zone, sc->order))
+ return watermark_ok;
+
+ /* If compaction is not ready to start, keep reclaiming */
+ if (!compaction_suitable(zone, sc->order))
+ return false;
+
+ return watermark_ok;
+}
+
+/*
+ * This is the direct reclaim path, for page-allocating processes. We only
+ * try to reclaim pages from zones which will satisfy the caller's allocation
+ * request.
+ *
+ * We reclaim from a zone even if that zone is over high_wmark_pages(zone).
+ * Because:
+ * a) The caller may be trying to free *extra* pages to satisfy a higher-order
+ * allocation or
+ * b) The target zone may be at high_wmark_pages(zone) but the lower zones
+ * must go *over* high_wmark_pages(zone) to satisfy the `incremental min'
+ * zone defense algorithm.
+ *
+ * If a zone is deemed to be full of pinned pages then just give it a light
+ * scan then give up on it.
+ *
+ * This function returns true if a zone is being reclaimed for a costly
+ * high-order allocation and compaction is ready to begin. This indicates to
+ * the caller that it should consider retrying the allocation instead of
+ * further reclaim.
+ */
+static bool shrink_zones(int priority, struct zonelist *zonelist,
+ struct scan_control *sc)
+{
+ struct zoneref *z;
+ struct zone *zone;
+ unsigned long nr_soft_reclaimed;
+ unsigned long nr_soft_scanned;
+ bool aborted_reclaim = false;
+
+ /*
+ * If the number of buffer_heads in the machine exceeds the maximum
+ * allowed level, force direct reclaim to scan the highmem zone as
+ * highmem pages could be pinning lowmem pages storing buffer_heads
+ */
+ if (buffer_heads_over_limit)
+ sc->gfp_mask |= __GFP_HIGHMEM;
+
+ for_each_zone_zonelist_nodemask(zone, z, zonelist,
+ gfp_zone(sc->gfp_mask), sc->nodemask) {
+ if (!populated_zone(zone))
+ continue;
+ /*
+ * Take care memory controller reclaiming has small influence
+ * to global LRU.
+ */
+ if (global_reclaim(sc)) {
+ if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
+ continue;
+ if (zone->all_unreclaimable && priority != DEF_PRIORITY)
+ continue; /* Let kswapd poll it */
+ if (COMPACTION_BUILD) {
+ /*
+ * If we already have plenty of memory free for
+ * compaction in this zone, don't free any more.
+ * Even though compaction is invoked for any
+ * non-zero order, only frequent costly order
+ * reclamation is disruptive enough to become a
+ * noticeable problem, like transparent huge
+ * page allocations.
+ */
+ if (compaction_ready(zone, sc)) {
+ aborted_reclaim = true;
+ continue;
+ }
+ }
+ /*
+ * This steals pages from memory cgroups over softlimit
+ * and returns the number of reclaimed pages and
+ * scanned pages. This works for global memory pressure
+ * and balancing, not for a memcg's limit.
+ */
+ nr_soft_scanned = 0;
+ nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone,
+ sc->order, sc->gfp_mask,
+ &nr_soft_scanned);
+ sc->nr_reclaimed += nr_soft_reclaimed;
+ sc->nr_scanned += nr_soft_scanned;
+ /* need some check for avoid more shrink_zone() */
+ }
+
+ shrink_zone(priority, zone, sc);
+ }
+
+ return aborted_reclaim;
+}
+
+static bool zone_reclaimable(struct zone *zone)
+{
+ return zone->pages_scanned < zone_reclaimable_pages(zone) * 6;
+}
+
+/* All zones in zonelist are unreclaimable? */
+static bool all_unreclaimable(struct zonelist *zonelist,
+ struct scan_control *sc)
+{
+ struct zoneref *z;
+ struct zone *zone;
+
+ for_each_zone_zonelist_nodemask(zone, z, zonelist,
+ gfp_zone(sc->gfp_mask), sc->nodemask) {
+ if (!populated_zone(zone))
+ continue;
+ if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
+ continue;
+ if (!zone->all_unreclaimable)
+ return false;
+ }
+
+ return true;
+}
+
+/*
+ * This is the main entry point to direct page reclaim.
+ *
+ * If a full scan of the inactive list fails to free enough memory then we
+ * are "out of memory" and something needs to be killed.
+ *
+ * If the caller is !__GFP_FS then the probability of a failure is reasonably
+ * high - the zone may be full of dirty or under-writeback pages, which this
+ * caller can't do much about. We kick the writeback threads and take explicit
+ * naps in the hope that some of these pages can be written. But if the
+ * allocating task holds filesystem locks which prevent writeout this might not
+ * work, and the allocation attempt will fail.
+ *
+ * returns: 0, if no pages reclaimed
+ * else, the number of pages reclaimed
+ */
+static unsigned long do_try_to_free_pages(struct zonelist *zonelist,
+ struct scan_control *sc,
+ struct shrink_control *shrink)
+{
+ int priority;
+ unsigned long total_scanned = 0;
+ struct reclaim_state *reclaim_state = current->reclaim_state;
+ struct zoneref *z;
+ struct zone *zone;
+ unsigned long writeback_threshold;
+ bool aborted_reclaim;
+
+ delayacct_freepages_start();
+
+ if (global_reclaim(sc))
+ count_vm_event(ALLOCSTALL);
+
+ for (priority = DEF_PRIORITY; priority >= 0; priority--) {
+#ifdef CONFIG_SPEED_OPT_DYNAMIC_POOL
+ extern void skb_sys_pool_delete(void);
+ skb_sys_pool_delete();
+#endif
+ sc->nr_scanned = 0;
+ if (!priority)
+ disable_swap_token(sc->target_mem_cgroup);
+ aborted_reclaim = shrink_zones(priority, zonelist, sc);
+
+ /*
+ * Don't shrink slabs when reclaiming memory from
+ * over limit cgroups
+ */
+ if (global_reclaim(sc)) {
+ unsigned long lru_pages = 0;
+ for_each_zone_zonelist(zone, z, zonelist,
+ gfp_zone(sc->gfp_mask)) {
+ if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
+ continue;
+
+ lru_pages += zone_reclaimable_pages(zone);
+ }
+
+ shrink_slab(shrink, sc->nr_scanned, lru_pages);
+ if (reclaim_state) {
+ sc->nr_reclaimed += reclaim_state->reclaimed_slab;
+ reclaim_state->reclaimed_slab = 0;
+ }
+ }
+ total_scanned += sc->nr_scanned;
+ if (sc->nr_reclaimed >= sc->nr_to_reclaim)
+ goto out;
+
+ /*
+ * Try to write back as many pages as we just scanned. This
+ * tends to cause slow streaming writers to write data to the
+ * disk smoothly, at the dirtying rate, which is nice. But
+ * that's undesirable in laptop mode, where we *want* lumpy
+ * writeout. So in laptop mode, write out the whole world.
+ */
+ writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2;
+ if (total_scanned > writeback_threshold) {
+ wakeup_flusher_threads(laptop_mode ? 0 : total_scanned,
+ WB_REASON_TRY_TO_FREE_PAGES);
+ sc->may_writepage = 1;
+ }
+
+ /* Take a nap, wait for some writeback to complete */
+ if (!sc->hibernation_mode && sc->nr_scanned &&
+ priority < DEF_PRIORITY - 2) {
+ struct zone *preferred_zone;
+
+ first_zones_zonelist(zonelist, gfp_zone(sc->gfp_mask),
+ &cpuset_current_mems_allowed,
+ &preferred_zone);
+ wait_iff_congested(preferred_zone, BLK_RW_ASYNC, HZ/10);
+ }
+ }
+
+out:
+ delayacct_freepages_end();
+
+ if (sc->nr_reclaimed)
+ return sc->nr_reclaimed;
+
+ /*
+ * As hibernation is going on, kswapd is freezed so that it can't mark
+ * the zone into all_unreclaimable. Thus bypassing all_unreclaimable
+ * check.
+ */
+ if (oom_killer_disabled)
+ return 0;
+
+ /* Aborted reclaim to try compaction? don't OOM, then */
+ if (aborted_reclaim)
+ return 1;
+
+ /* top priority shrink_zones still had more to do? don't OOM, then */
+ if (global_reclaim(sc) && !all_unreclaimable(zonelist, sc))
+ return 1;
+
+ return 0;
+}
+
+unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
+ gfp_t gfp_mask, nodemask_t *nodemask)
+{
+ unsigned long nr_reclaimed;
+ struct scan_control sc = {
+ .gfp_mask = gfp_mask,
+ .may_writepage = !laptop_mode,
+ .nr_to_reclaim = SWAP_CLUSTER_MAX,
+ .may_unmap = 1,
+ .may_swap = 1,
+ .order = order,
+ .target_mem_cgroup = NULL,
+ .nodemask = nodemask,
+ };
+ struct shrink_control shrink = {
+ .gfp_mask = sc.gfp_mask,
+ };
+
+ trace_mm_vmscan_direct_reclaim_begin(order,
+ sc.may_writepage,
+ gfp_mask);
+
+ nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
+
+ trace_mm_vmscan_direct_reclaim_end(nr_reclaimed);
+
+ return nr_reclaimed;
+}
+
+#ifdef CONFIG_CGROUP_MEM_RES_CTLR
+
+unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *memcg,
+ gfp_t gfp_mask, bool noswap,
+ struct zone *zone,
+ unsigned long *nr_scanned)
+{
+ struct scan_control sc = {
+ .nr_scanned = 0,
+ .nr_to_reclaim = SWAP_CLUSTER_MAX,
+ .may_writepage = !laptop_mode,
+ .may_unmap = 1,
+ .may_swap = !noswap,
+ .order = 0,
+ .target_mem_cgroup = memcg,
+ };
+ struct mem_cgroup_zone mz = {
+ .mem_cgroup = memcg,
+ .zone = zone,
+ };
+
+ sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
+ (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
+
+ trace_mm_vmscan_memcg_softlimit_reclaim_begin(0,
+ sc.may_writepage,
+ sc.gfp_mask);
+
+ /*
+ * NOTE: Although we can get the priority field, using it
+ * here is not a good idea, since it limits the pages we can scan.
+ * if we don't reclaim here, the shrink_zone from balance_pgdat
+ * will pick up pages from other mem cgroup's as well. We hack
+ * the priority and make it zero.
+ */
+ shrink_mem_cgroup_zone(0, &mz, &sc);
+
+ trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed);
+
+ *nr_scanned = sc.nr_scanned;
+ return sc.nr_reclaimed;
+}
+
+unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
+ gfp_t gfp_mask,
+ bool noswap)
+{
+ struct zonelist *zonelist;
+ unsigned long nr_reclaimed;
+ int nid;
+ struct scan_control sc = {
+ .may_writepage = !laptop_mode,
+ .may_unmap = 1,
+ .may_swap = !noswap,
+ .nr_to_reclaim = SWAP_CLUSTER_MAX,
+ .order = 0,
+ .target_mem_cgroup = memcg,
+ .nodemask = NULL, /* we don't care the placement */
+ .gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
+ (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK),
+ };
+ struct shrink_control shrink = {
+ .gfp_mask = sc.gfp_mask,
+ };
+
+ /*
+ * Unlike direct reclaim via alloc_pages(), memcg's reclaim doesn't
+ * take care of from where we get pages. So the node where we start the
+ * scan does not need to be the current node.
+ */
+ nid = mem_cgroup_select_victim_node(memcg);
+
+ zonelist = NODE_DATA(nid)->node_zonelists;
+
+ trace_mm_vmscan_memcg_reclaim_begin(0,
+ sc.may_writepage,
+ sc.gfp_mask);
+
+ nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
+
+ trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed);
+
+ return nr_reclaimed;
+}
+#endif
+
+static void age_active_anon(struct zone *zone, struct scan_control *sc,
+ int priority)
+{
+ struct mem_cgroup *memcg;
+
+ if (!total_swap_pages)
+ return;
+
+ memcg = mem_cgroup_iter(NULL, NULL, NULL);
+ do {
+ struct mem_cgroup_zone mz = {
+ .mem_cgroup = memcg,
+ .zone = zone,
+ };
+
+ if (inactive_anon_is_low(&mz))
+ shrink_active_list(SWAP_CLUSTER_MAX, &mz,
+ sc, priority, 0);
+
+ memcg = mem_cgroup_iter(NULL, memcg, NULL);
+ } while (memcg);
+}
+
+static bool zone_balanced(struct zone *zone, int order,
+ unsigned long balance_gap, int classzone_idx)
+{
+ if (!zone_watermark_ok_safe(zone, order, high_wmark_pages(zone) +
+ balance_gap, classzone_idx, 0))
+ return false;
+
+ if (COMPACTION_BUILD && order && !compaction_suitable(zone, order))
+ return false;
+
+ return true;
+}
+
+/*
+ * pgdat_balanced is used when checking if a node is balanced for high-order
+ * allocations. Only zones that meet watermarks and are in a zone allowed
+ * by the callers classzone_idx are added to balanced_pages. The total of
+ * balanced pages must be at least 25% of the zones allowed by classzone_idx
+ * for the node to be considered balanced. Forcing all zones to be balanced
+ * for high orders can cause excessive reclaim when there are imbalanced zones.
+ * The choice of 25% is due to
+ * o a 16M DMA zone that is balanced will not balance a zone on any
+ * reasonable sized machine
+ * o On all other machines, the top zone must be at least a reasonable
+ * percentage of the middle zones. For example, on 32-bit x86, highmem
+ * would need to be at least 256M for it to be balance a whole node.
+ * Similarly, on x86-64 the Normal zone would need to be at least 1G
+ * to balance a node on its own. These seemed like reasonable ratios.
+ */
+static bool pgdat_balanced(pg_data_t *pgdat, unsigned long balanced_pages,
+ int classzone_idx)
+{
+ unsigned long present_pages = 0;
+ int i;
+
+ for (i = 0; i <= classzone_idx; i++)
+ present_pages += pgdat->node_zones[i].present_pages;
+
+ /* A special case here: if zone has no page, we think it's balanced */
+ return balanced_pages >= (present_pages >> 2);
+}
+
+/* is kswapd sleeping prematurely? */
+static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remaining,
+ int classzone_idx)
+{
+ int i;
+ unsigned long balanced = 0;
+ bool all_zones_ok = true;
+
+ /* If a direct reclaimer woke kswapd within HZ/10, it's premature */
+ if (remaining)
+ return true;
+
+ /* Check the watermark levels */
+ for (i = 0; i <= classzone_idx; i++) {
+ struct zone *zone = pgdat->node_zones + i;
+
+ if (!populated_zone(zone))
+ continue;
+
+ /*
+ * balance_pgdat() skips over all_unreclaimable after
+ * DEF_PRIORITY. Effectively, it considers them balanced so
+ * they must be considered balanced here as well if kswapd
+ * is to sleep
+ */
+ if (zone->all_unreclaimable) {
+ balanced += zone->present_pages;
+ continue;
+ }
+
+ if (!zone_balanced(zone, order, 0, i))
+ all_zones_ok = false;
+ else
+ balanced += zone->present_pages;
+ }
+
+ /*
+ * For high-order requests, the balanced zones must contain at least
+ * 25% of the nodes pages for kswapd to sleep. For order-0, all zones
+ * must be balanced
+ */
+ if (order)
+ return !pgdat_balanced(pgdat, balanced, classzone_idx);
+ else
+ return !all_zones_ok;
+}
+
+/*
+ * For kswapd, balance_pgdat() will work across all this node's zones until
+ * they are all at high_wmark_pages(zone).
+ *
+ * Returns the final order kswapd was reclaiming at
+ *
+ * There is special handling here for zones which are full of pinned pages.
+ * This can happen if the pages are all mlocked, or if they are all used by
+ * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb.
+ * What we do is to detect the case where all pages in the zone have been
+ * scanned twice and there has been zero successful reclaim. Mark the zone as
+ * dead and from now on, only perform a short scan. Basically we're polling
+ * the zone for when the problem goes away.
+ *
+ * kswapd scans the zones in the highmem->normal->dma direction. It skips
+ * zones which have free_pages > high_wmark_pages(zone), but once a zone is
+ * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the
+ * lower zones regardless of the number of free pages in the lower zones. This
+ * interoperates with the page allocator fallback scheme to ensure that aging
+ * of pages is balanced across the zones.
+ */
+static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
+ int *classzone_idx)
+{
+ int all_zones_ok;
+ unsigned long balanced;
+ int priority;
+ int i;
+ int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
+ unsigned long total_scanned;
+ struct reclaim_state *reclaim_state = current->reclaim_state;
+ unsigned long nr_soft_reclaimed;
+ unsigned long nr_soft_scanned;
+ struct scan_control sc = {
+ .gfp_mask = GFP_KERNEL,
+ .may_unmap = 1,
+ .may_swap = 1,
+ /*
+ * kswapd doesn't want to be bailed out while reclaim. because
+ * we want to put equal scanning pressure on each zone.
+ */
+ .nr_to_reclaim = ULONG_MAX,
+ .order = order,
+ .target_mem_cgroup = NULL,
+ };
+ struct shrink_control shrink = {
+ .gfp_mask = sc.gfp_mask,
+ };
+loop_again:
+ total_scanned = 0;
+ sc.nr_reclaimed = 0;
+ sc.may_writepage = !laptop_mode;
+ count_vm_event(PAGEOUTRUN);
+
+ for (priority = DEF_PRIORITY; priority >= 0; priority--) {
+ unsigned long lru_pages = 0;
+ int has_under_min_watermark_zone = 0;
+
+ /* The swap token gets in the way of swapout... */
+ if (!priority)
+ disable_swap_token(NULL);
+
+ all_zones_ok = 1;
+ balanced = 0;
+
+ /*
+ * Scan in the highmem->dma direction for the highest
+ * zone which needs scanning
+ */
+ for (i = pgdat->nr_zones - 1; i >= 0; i--) {
+ struct zone *zone = pgdat->node_zones + i;
+
+ if (!populated_zone(zone))
+ continue;
+
+ if (zone->all_unreclaimable && priority != DEF_PRIORITY)
+ continue;
+
+ /*
+ * Do some background aging of the anon list, to give
+ * pages a chance to be referenced before reclaiming.
+ */
+ age_active_anon(zone, &sc, priority);
+
+ /*
+ * If the number of buffer_heads in the machine
+ * exceeds the maximum allowed level and this node
+ * has a highmem zone, force kswapd to reclaim from
+ * it to relieve lowmem pressure.
+ */
+ if (buffer_heads_over_limit && is_highmem_idx(i)) {
+ end_zone = i;
+ break;
+ }
+
+ if (!zone_balanced(zone, order, 0, 0)) {
+ end_zone = i;
+ break;
+ } else {
+ /* If balanced, clear the congested flag */
+ zone_clear_flag(zone, ZONE_CONGESTED);
+ }
+ }
+ if (i < 0)
+ goto out;
+
+ for (i = 0; i <= end_zone; i++) {
+ struct zone *zone = pgdat->node_zones + i;
+
+ lru_pages += zone_reclaimable_pages(zone);
+ }
+
+ /*
+ * Now scan the zone in the dma->highmem direction, stopping
+ * at the last zone which needs scanning.
+ *
+ * We do this because the page allocator works in the opposite
+ * direction. This prevents the page allocator from allocating
+ * pages behind kswapd's direction of progress, which would
+ * cause too much scanning of the lower zones.
+ */
+ for (i = 0; i <= end_zone; i++) {
+ struct zone *zone = pgdat->node_zones + i;
+ int nr_slab, testorder;
+ unsigned long balance_gap;
+
+ if (!populated_zone(zone))
+ continue;
+
+ if (zone->all_unreclaimable && priority != DEF_PRIORITY)
+ continue;
+
+ sc.nr_scanned = 0;
+
+ nr_soft_scanned = 0;
+ /*
+ * Call soft limit reclaim before calling shrink_zone.
+ */
+ nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone,
+ order, sc.gfp_mask,
+ &nr_soft_scanned);
+ sc.nr_reclaimed += nr_soft_reclaimed;
+ total_scanned += nr_soft_scanned;
+
+ /*
+ * We put equal pressure on every zone, unless
+ * one zone has way too many pages free
+ * already. The "too many pages" is defined
+ * as the high wmark plus a "gap" where the
+ * gap is either the low watermark or 1%
+ * of the zone, whichever is smaller.
+ */
+ balance_gap = min(low_wmark_pages(zone),
+ (zone->present_pages +
+ KSWAPD_ZONE_BALANCE_GAP_RATIO-1) /
+ KSWAPD_ZONE_BALANCE_GAP_RATIO);
+ /*
+ * Kswapd reclaims only single pages with compaction
+ * enabled. Trying too hard to reclaim until contiguous
+ * free pages have become available can hurt performance
+ * by evicting too much useful data from memory.
+ * Do not reclaim more than needed for compaction.
+ */
+ testorder = order;
+ if (COMPACTION_BUILD && order &&
+ compaction_suitable(zone, order) !=
+ COMPACT_SKIPPED)
+ testorder = 0;
+
+ if ((buffer_heads_over_limit && is_highmem_idx(i)) ||
+ !zone_balanced(zone, testorder,
+ balance_gap, end_zone)) {
+ shrink_zone(priority, zone, &sc);
+
+ reclaim_state->reclaimed_slab = 0;
+ nr_slab = shrink_slab(&shrink, sc.nr_scanned, lru_pages);
+ sc.nr_reclaimed += reclaim_state->reclaimed_slab;
+ total_scanned += sc.nr_scanned;
+
+ if (nr_slab == 0 && !zone_reclaimable(zone))
+ zone->all_unreclaimable = 1;
+ }
+
+ /*
+ * If we've done a decent amount of scanning and
+ * the reclaim ratio is low, start doing writepage
+ * even in laptop mode
+ */
+ if (total_scanned > SWAP_CLUSTER_MAX * 2 &&
+ total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2)
+ sc.may_writepage = 1;
+
+ if (zone->all_unreclaimable) {
+ if (end_zone && end_zone == i)
+ end_zone--;
+ continue;
+ }
+
+ if (!zone_balanced(zone, testorder, 0, end_zone)) {
+ all_zones_ok = 0;
+ /*
+ * We are still under min water mark. This
+ * means that we have a GFP_ATOMIC allocation
+ * failure risk. Hurry up!
+ */
+ if (!zone_watermark_ok_safe(zone, order,
+ min_wmark_pages(zone), end_zone, 0))
+ has_under_min_watermark_zone = 1;
+ } else {
+ /*
+ * If a zone reaches its high watermark,
+ * consider it to be no longer congested. It's
+ * possible there are dirty pages backed by
+ * congested BDIs but as pressure is relieved,
+ * spectulatively avoid congestion waits
+ */
+ zone_clear_flag(zone, ZONE_CONGESTED);
+ if (i <= *classzone_idx)
+ balanced += zone->present_pages;
+ }
+
+ }
+ if (all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))
+ break; /* kswapd: all done */
+ /*
+ * OK, kswapd is getting into trouble. Take a nap, then take
+ * another pass across the zones.
+ */
+ if (total_scanned && (priority < DEF_PRIORITY - 2)) {
+ if (has_under_min_watermark_zone)
+ count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT);
+ else
+ congestion_wait(BLK_RW_ASYNC, HZ/10);
+ }
+
+ /*
+ * We do this so kswapd doesn't build up large priorities for
+ * example when it is freeing in parallel with allocators. It
+ * matches the direct reclaim path behaviour in terms of impact
+ * on zone->*_priority.
+ */
+ if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX)
+ break;
+ }
+out:
+
+ /*
+ * order-0: All zones must meet high watermark for a balanced node
+ * high-order: Balanced zones must make up at least 25% of the node
+ * for the node to be balanced
+ */
+ if (!(all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))) {
+ cond_resched();
+
+ try_to_freeze();
+
+ /*
+ * Fragmentation may mean that the system cannot be
+ * rebalanced for high-order allocations in all zones.
+ * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX,
+ * it means the zones have been fully scanned and are still
+ * not balanced. For high-order allocations, there is
+ * little point trying all over again as kswapd may
+ * infinite loop.
+ *
+ * Instead, recheck all watermarks at order-0 as they
+ * are the most important. If watermarks are ok, kswapd will go
+ * back to sleep. High-order users can still perform direct
+ * reclaim if they wish.
+ */
+ if (sc.nr_reclaimed < SWAP_CLUSTER_MAX)
+ order = sc.order = 0;
+
+ goto loop_again;
+ }
+
+ /*
+ * If kswapd was reclaiming at a higher order, it has the option of
+ * sleeping without all zones being balanced. Before it does, it must
+ * ensure that the watermarks for order-0 on *all* zones are met and
+ * that the congestion flags are cleared. The congestion flag must
+ * be cleared as kswapd is the only mechanism that clears the flag
+ * and it is potentially going to sleep here.
+ */
+ if (order) {
+ int zones_need_compaction = 1;
+
+ for (i = 0; i <= end_zone; i++) {
+ struct zone *zone = pgdat->node_zones + i;
+
+ if (!populated_zone(zone))
+ continue;
+
+ if (zone->all_unreclaimable && priority != DEF_PRIORITY)
+ continue;
+
+ /* Would compaction fail due to lack of free memory? */
+ if (COMPACTION_BUILD &&
+ compaction_suitable(zone, order) == COMPACT_SKIPPED)
+ goto loop_again;
+
+ /* Confirm the zone is balanced for order-0 */
+ if (!zone_watermark_ok(zone, 0,
+ high_wmark_pages(zone), 0, 0)) {
+ order = sc.order = 0;
+ goto loop_again;
+ }
+
+ /* Check if the memory needs to be defragmented. */
+ if (zone_watermark_ok(zone, order,
+ low_wmark_pages(zone), *classzone_idx, 0))
+ zones_need_compaction = 0;
+
+ /* If balanced, clear the congested flag */
+ zone_clear_flag(zone, ZONE_CONGESTED);
+ }
+
+ if (zones_need_compaction)
+ compact_pgdat(pgdat, order);
+ }
+
+ /*
+ * Return the order we were reclaiming at so sleeping_prematurely()
+ * makes a decision on the order we were last reclaiming at. However,
+ * if another caller entered the allocator slow path while kswapd
+ * was awake, order will remain at the higher level
+ */
+ *classzone_idx = end_zone;
+ return order;
+}
+
+static void kswapd_try_to_sleep(pg_data_t *pgdat, int order, int classzone_idx)
+{
+ long remaining = 0;
+ DEFINE_WAIT(wait);
+
+ if (freezing(current) || kthread_should_stop())
+ return;
+
+ prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
+
+ /* Try to sleep for a short interval */
+ if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) {
+ remaining = schedule_timeout(HZ/10);
+ finish_wait(&pgdat->kswapd_wait, &wait);
+ prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE);
+ }
+
+ /*
+ * After a short sleep, check if it was a premature sleep. If not, then
+ * go fully to sleep until explicitly woken up.
+ */
+ if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) {
+ trace_mm_vmscan_kswapd_sleep(pgdat->node_id);
+
+ /*
+ * vmstat counters are not perfectly accurate and the estimated
+ * value for counters such as NR_FREE_PAGES can deviate from the
+ * true value by nr_online_cpus * threshold. To avoid the zone
+ * watermarks being breached while under pressure, we reduce the
+ * per-cpu vmstat threshold while kswapd is awake and restore
+ * them before going back to sleep.
+ */
+ set_pgdat_percpu_threshold(pgdat, calculate_normal_threshold);
+
+ if (!kthread_should_stop())
+ schedule();
+
+ set_pgdat_percpu_threshold(pgdat, calculate_pressure_threshold);
+ } else {
+ if (remaining)
+ count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY);
+ else
+ count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY);
+ }
+ finish_wait(&pgdat->kswapd_wait, &wait);
+}
+
+/*
+ * The background pageout daemon, started as a kernel thread
+ * from the init process.
+ *
+ * This basically trickles out pages so that we have _some_
+ * free memory available even if there is no other activity
+ * that frees anything up. This is needed for things like routing
+ * etc, where we otherwise might have all activity going on in
+ * asynchronous contexts that cannot page things out.
+ *
+ * If there are applications that are active memory-allocators
+ * (most normal use), this basically shouldn't matter.
+ */
+static int kswapd(void *p)
+{
+ unsigned long order, new_order;
+ unsigned balanced_order;
+ int classzone_idx, new_classzone_idx;
+ int balanced_classzone_idx;
+ pg_data_t *pgdat = (pg_data_t*)p;
+ struct task_struct *tsk = current;
+
+ struct reclaim_state reclaim_state = {
+ .reclaimed_slab = 0,
+ };
+ const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
+
+ lockdep_set_current_reclaim_state(GFP_KERNEL);
+
+ if (!cpumask_empty(cpumask))
+ set_cpus_allowed_ptr(tsk, cpumask);
+ current->reclaim_state = &reclaim_state;
+
+ /*
+ * Tell the memory management that we're a "memory allocator",
+ * and that if we need more memory we should get access to it
+ * regardless (see "__alloc_pages()"). "kswapd" should
+ * never get caught in the normal page freeing logic.
+ *
+ * (Kswapd normally doesn't need memory anyway, but sometimes
+ * you need a small amount of memory in order to be able to
+ * page out something else, and this flag essentially protects
+ * us from recursively trying to free more memory as we're
+ * trying to free the first piece of memory in the first place).
+ */
+ tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD;
+ set_freezable();
+
+ order = new_order = 0;
+ balanced_order = 0;
+ classzone_idx = new_classzone_idx = pgdat->nr_zones - 1;
+ balanced_classzone_idx = classzone_idx;
+ for ( ; ; ) {
+ int ret;
+
+ /*
+ * If the last balance_pgdat was unsuccessful it's unlikely a
+ * new request of a similar or harder type will succeed soon
+ * so consider going to sleep on the basis we reclaimed at
+ */
+ if (balanced_classzone_idx >= new_classzone_idx &&
+ balanced_order == new_order) {
+ new_order = pgdat->kswapd_max_order;
+ new_classzone_idx = pgdat->classzone_idx;
+ pgdat->kswapd_max_order = 0;
+ pgdat->classzone_idx = pgdat->nr_zones - 1;
+ }
+
+ if (order < new_order || classzone_idx > new_classzone_idx) {
+ /*
+ * Don't sleep if someone wants a larger 'order'
+ * allocation or has tigher zone constraints
+ */
+ order = new_order;
+ classzone_idx = new_classzone_idx;
+ } else {
+ kswapd_try_to_sleep(pgdat, balanced_order,
+ balanced_classzone_idx);
+ order = pgdat->kswapd_max_order;
+ classzone_idx = pgdat->classzone_idx;
+ new_order = order;
+ new_classzone_idx = classzone_idx;
+ pgdat->kswapd_max_order = 0;
+ pgdat->classzone_idx = pgdat->nr_zones - 1;
+ }
+
+ ret = try_to_freeze();
+ if (kthread_should_stop())
+ break;
+
+ /*
+ * We can speed up thawing tasks if we don't call balance_pgdat
+ * after returning from the refrigerator
+ */
+ if (!ret) {
+ trace_mm_vmscan_kswapd_wake(pgdat->node_id, order);
+ balanced_classzone_idx = classzone_idx;
+ balanced_order = balance_pgdat(pgdat, order,
+ &balanced_classzone_idx);
+ }
+ }
+
+ tsk->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD);
+ current->reclaim_state = NULL;
+ lockdep_clear_current_reclaim_state();
+
+ return 0;
+}
+
+/*
+ * A zone is low on free memory, so wake its kswapd task to service it.
+ */
+void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx)
+{
+ pg_data_t *pgdat;
+
+ if (!populated_zone(zone))
+ return;
+
+ if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
+ return;
+ pgdat = zone->zone_pgdat;
+ if (pgdat->kswapd_max_order < order) {
+ pgdat->kswapd_max_order = order;
+ pgdat->classzone_idx = min(pgdat->classzone_idx, classzone_idx);
+ }
+ if (!waitqueue_active(&pgdat->kswapd_wait))
+ return;
+ if (zone_watermark_ok_safe(zone, order, low_wmark_pages(zone), 0, 0))
+ return;
+
+ trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, zone_idx(zone), order);
+ wake_up_interruptible(&pgdat->kswapd_wait);
+}
+
+/*
+ * The reclaimable count would be mostly accurate.
+ * The less reclaimable pages may be
+ * - mlocked pages, which will be moved to unevictable list when encountered
+ * - mapped pages, which may require several travels to be reclaimed
+ * - dirty pages, which is not "instantly" reclaimable
+ */
+unsigned long global_reclaimable_pages(void)
+{
+ int nr;
+
+ nr = global_page_state(NR_ACTIVE_FILE) +
+ global_page_state(NR_INACTIVE_FILE);
+
+ if (nr_swap_pages > 0)
+ nr += global_page_state(NR_ACTIVE_ANON) +
+ global_page_state(NR_INACTIVE_ANON);
+
+ return nr;
+}
+
+unsigned long zone_reclaimable_pages(struct zone *zone)
+{
+ int nr;
+
+ nr = zone_page_state(zone, NR_ACTIVE_FILE) +
+ zone_page_state(zone, NR_INACTIVE_FILE);
+
+ if (nr_swap_pages > 0)
+ nr += zone_page_state(zone, NR_ACTIVE_ANON) +
+ zone_page_state(zone, NR_INACTIVE_ANON);
+
+ return nr;
+}
+
+#ifdef CONFIG_HIBERNATION
+/*
+ * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of
+ * freed pages.
+ *
+ * Rather than trying to age LRUs the aim is to preserve the overall
+ * LRU order by reclaiming preferentially
+ * inactive > active > active referenced > active mapped
+ */
+unsigned long shrink_all_memory(unsigned long nr_to_reclaim)
+{
+ struct reclaim_state reclaim_state;
+ struct scan_control sc = {
+ .gfp_mask = GFP_HIGHUSER_MOVABLE,
+ .may_swap = 1,
+ .may_unmap = 1,
+ .may_writepage = 1,
+ .nr_to_reclaim = nr_to_reclaim,
+ .hibernation_mode = 1,
+ .order = 0,
+ };
+ struct shrink_control shrink = {
+ .gfp_mask = sc.gfp_mask,
+ };
+ struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask);
+ struct task_struct *p = current;
+ unsigned long nr_reclaimed;
+
+ p->flags |= PF_MEMALLOC;
+ lockdep_set_current_reclaim_state(sc.gfp_mask);
+ reclaim_state.reclaimed_slab = 0;
+ p->reclaim_state = &reclaim_state;
+
+ nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
+
+ p->reclaim_state = NULL;
+ lockdep_clear_current_reclaim_state();
+ p->flags &= ~PF_MEMALLOC;
+
+ return nr_reclaimed;
+}
+#endif /* CONFIG_HIBERNATION */
+
+/* It's optimal to keep kswapds on the same CPUs as their memory, but
+ not required for correctness. So if the last cpu in a node goes
+ away, we get changed to run anywhere: as the first one comes back,
+ restore their cpu bindings. */
+static int __devinit cpu_callback(struct notifier_block *nfb,
+ unsigned long action, void *hcpu)
+{
+ int nid;
+
+ if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) {
+ for_each_node_state(nid, N_HIGH_MEMORY) {
+ pg_data_t *pgdat = NODE_DATA(nid);
+ const struct cpumask *mask;
+
+ mask = cpumask_of_node(pgdat->node_id);
+
+ if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
+ /* One of our CPUs online: restore mask */
+ set_cpus_allowed_ptr(pgdat->kswapd, mask);
+ }
+ }
+ return NOTIFY_OK;
+}
+
+/*
+ * This kswapd start function will be called by init and node-hot-add.
+ * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
+ */
+int kswapd_run(int nid)
+{
+ pg_data_t *pgdat = NODE_DATA(nid);
+ int ret = 0;
+
+ if (pgdat->kswapd)
+ return 0;
+
+ pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
+ if (IS_ERR(pgdat->kswapd)) {
+ /* failure at boot is fatal */
+ BUG_ON(system_state == SYSTEM_BOOTING);
+ printk("Failed to start kswapd on node %d\n",nid);
+ ret = -1;
+ }
+ return ret;
+}
+
+/*
+ * Called by memory hotplug when all memory in a node is offlined. Caller must
+ * hold lock_memory_hotplug().
+ */
+void kswapd_stop(int nid)
+{
+ struct task_struct *kswapd = NODE_DATA(nid)->kswapd;
+
+ if (kswapd) {
+ kthread_stop(kswapd);
+ NODE_DATA(nid)->kswapd = NULL;
+ }
+}
+
+static int __init kswapd_init(void)
+{
+ int nid;
+
+ swap_setup();
+ for_each_node_state(nid, N_HIGH_MEMORY)
+ kswapd_run(nid);
+ hotcpu_notifier(cpu_callback, 0);
+ return 0;
+}
+
+module_init(kswapd_init)
+
+#ifdef CONFIG_NUMA
+/*
+ * Zone reclaim mode
+ *
+ * If non-zero call zone_reclaim when the number of free pages falls below
+ * the watermarks.
+ */
+int zone_reclaim_mode __read_mostly;
+
+#define RECLAIM_OFF 0
+#define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */
+#define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */
+#define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */
+
+/*
+ * Priority for ZONE_RECLAIM. This determines the fraction of pages
+ * of a node considered for each zone_reclaim. 4 scans 1/16th of
+ * a zone.
+ */
+#define ZONE_RECLAIM_PRIORITY 4
+
+/*
+ * Percentage of pages in a zone that must be unmapped for zone_reclaim to
+ * occur.
+ */
+int sysctl_min_unmapped_ratio = 1;
+
+/*
+ * If the number of slab pages in a zone grows beyond this percentage then
+ * slab reclaim needs to occur.
+ */
+int sysctl_min_slab_ratio = 5;
+
+static inline unsigned long zone_unmapped_file_pages(struct zone *zone)
+{
+ unsigned long file_mapped = zone_page_state(zone, NR_FILE_MAPPED);
+ unsigned long file_lru = zone_page_state(zone, NR_INACTIVE_FILE) +
+ zone_page_state(zone, NR_ACTIVE_FILE);
+
+ /*
+ * It's possible for there to be more file mapped pages than
+ * accounted for by the pages on the file LRU lists because
+ * tmpfs pages accounted for as ANON can also be FILE_MAPPED
+ */
+ return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0;
+}
+
+/* Work out how many page cache pages we can reclaim in this reclaim_mode */
+static long zone_pagecache_reclaimable(struct zone *zone)
+{
+ long nr_pagecache_reclaimable;
+ long delta = 0;
+
+ /*
+ * If RECLAIM_SWAP is set, then all file pages are considered
+ * potentially reclaimable. Otherwise, we have to worry about
+ * pages like swapcache and zone_unmapped_file_pages() provides
+ * a better estimate
+ */
+ if (zone_reclaim_mode & RECLAIM_SWAP)
+ nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES);
+ else
+ nr_pagecache_reclaimable = zone_unmapped_file_pages(zone);
+
+ /* If we can't clean pages, remove dirty pages from consideration */
+ if (!(zone_reclaim_mode & RECLAIM_WRITE))
+ delta += zone_page_state(zone, NR_FILE_DIRTY);
+
+ /* Watch for any possible underflows due to delta */
+ if (unlikely(delta > nr_pagecache_reclaimable))
+ delta = nr_pagecache_reclaimable;
+
+ return nr_pagecache_reclaimable - delta;
+}
+
+/*
+ * Try to free up some pages from this zone through reclaim.
+ */
+static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
+{
+ /* Minimum pages needed in order to stay on node */
+ const unsigned long nr_pages = 1 << order;
+ struct task_struct *p = current;
+ struct reclaim_state reclaim_state;
+ int priority;
+ struct scan_control sc = {
+ .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE),
+ .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP),
+ .may_swap = 1,
+ .nr_to_reclaim = max_t(unsigned long, nr_pages,
+ SWAP_CLUSTER_MAX),
+ .gfp_mask = gfp_mask,
+ .order = order,
+ };
+ struct shrink_control shrink = {
+ .gfp_mask = sc.gfp_mask,
+ };
+ unsigned long nr_slab_pages0, nr_slab_pages1;
+
+ cond_resched();
+ /*
+ * We need to be able to allocate from the reserves for RECLAIM_SWAP
+ * and we also need to be able to write out pages for RECLAIM_WRITE
+ * and RECLAIM_SWAP.
+ */
+ p->flags |= PF_MEMALLOC | PF_SWAPWRITE;
+ lockdep_set_current_reclaim_state(gfp_mask);
+ reclaim_state.reclaimed_slab = 0;
+ p->reclaim_state = &reclaim_state;
+
+ if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) {
+ /*
+ * Free memory by calling shrink zone with increasing
+ * priorities until we have enough memory freed.
+ */
+ priority = ZONE_RECLAIM_PRIORITY;
+ do {
+ shrink_zone(priority, zone, &sc);
+ priority--;
+ } while (priority >= 0 && sc.nr_reclaimed < nr_pages);
+ }
+
+ nr_slab_pages0 = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
+ if (nr_slab_pages0 > zone->min_slab_pages) {
+ /*
+ * shrink_slab() does not currently allow us to determine how
+ * many pages were freed in this zone. So we take the current
+ * number of slab pages and shake the slab until it is reduced
+ * by the same nr_pages that we used for reclaiming unmapped
+ * pages.
+ *
+ * Note that shrink_slab will free memory on all zones and may
+ * take a long time.
+ */
+ for (;;) {
+ unsigned long lru_pages = zone_reclaimable_pages(zone);
+
+ /* No reclaimable slab or very low memory pressure */
+ if (!shrink_slab(&shrink, sc.nr_scanned, lru_pages))
+ break;
+
+ /* Freed enough memory */
+ nr_slab_pages1 = zone_page_state(zone,
+ NR_SLAB_RECLAIMABLE);
+ if (nr_slab_pages1 + nr_pages <= nr_slab_pages0)
+ break;
+ }
+
+ /*
+ * Update nr_reclaimed by the number of slab pages we
+ * reclaimed from this zone.
+ */
+ nr_slab_pages1 = zone_page_state(zone, NR_SLAB_RECLAIMABLE);
+ if (nr_slab_pages1 < nr_slab_pages0)
+ sc.nr_reclaimed += nr_slab_pages0 - nr_slab_pages1;
+ }
+
+ p->reclaim_state = NULL;
+ current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE);
+ lockdep_clear_current_reclaim_state();
+ return sc.nr_reclaimed >= nr_pages;
+}
+
+int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
+{
+ int node_id;
+ int ret;
+
+ /*
+ * Zone reclaim reclaims unmapped file backed pages and
+ * slab pages if we are over the defined limits.
+ *
+ * A small portion of unmapped file backed pages is needed for
+ * file I/O otherwise pages read by file I/O will be immediately
+ * thrown out if the zone is overallocated. So we do not reclaim
+ * if less than a specified percentage of the zone is used by
+ * unmapped file backed pages.
+ */
+ if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages &&
+ zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages)
+ return ZONE_RECLAIM_FULL;
+
+ if (zone->all_unreclaimable)
+ return ZONE_RECLAIM_FULL;
+
+ /*
+ * Do not scan if the allocation should not be delayed.
+ */
+ if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC))
+ return ZONE_RECLAIM_NOSCAN;
+
+ /*
+ * Only run zone reclaim on the local zone or on zones that do not
+ * have associated processors. This will favor the local processor
+ * over remote processors and spread off node memory allocations
+ * as wide as possible.
+ */
+ node_id = zone_to_nid(zone);
+ if (node_state(node_id, N_CPU) && node_id != numa_node_id())
+ return ZONE_RECLAIM_NOSCAN;
+
+ if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED))
+ return ZONE_RECLAIM_NOSCAN;
+
+ ret = __zone_reclaim(zone, gfp_mask, order);
+ zone_clear_flag(zone, ZONE_RECLAIM_LOCKED);
+
+ if (!ret)
+ count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED);
+
+ return ret;
+}
+#endif
+
+/*
+ * page_evictable - test whether a page is evictable
+ * @page: the page to test
+ * @vma: the VMA in which the page is or will be mapped, may be NULL
+ *
+ * Test whether page is evictable--i.e., should be placed on active/inactive
+ * lists vs unevictable list. The vma argument is !NULL when called from the
+ * fault path to determine how to instantate a new page.
+ *
+ * Reasons page might not be evictable:
+ * (1) page's mapping marked unevictable
+ * (2) page is part of an mlocked VMA
+ *
+ */
+int page_evictable(struct page *page, struct vm_area_struct *vma)
+{
+
+ if (mapping_unevictable(page_mapping(page)))
+ return 0;
+
+ if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page)))
+ return 0;
+
+ return 1;
+}
+
+#ifdef CONFIG_SHMEM
+/**
+ * check_move_unevictable_pages - check pages for evictability and move to appropriate zone lru list
+ * @pages: array of pages to check
+ * @nr_pages: number of pages to check
+ *
+ * Checks pages for evictability and moves them to the appropriate lru list.
+ *
+ * This function is only used for SysV IPC SHM_UNLOCK.
+ */
+void check_move_unevictable_pages(struct page **pages, int nr_pages)
+{
+ struct lruvec *lruvec;
+ struct zone *zone = NULL;
+ int pgscanned = 0;
+ int pgrescued = 0;
+ int i;
+
+ for (i = 0; i < nr_pages; i++) {
+ struct page *page = pages[i];
+ struct zone *pagezone;
+
+ pgscanned++;
+ pagezone = page_zone(page);
+ if (pagezone != zone) {
+ if (zone)
+ spin_unlock_irq(&zone->lru_lock);
+ zone = pagezone;
+ spin_lock_irq(&zone->lru_lock);
+ }
+
+ if (!PageLRU(page) || !PageUnevictable(page))
+ continue;
+
+ if (page_evictable(page, NULL)) {
+ enum lru_list lru = page_lru_base_type(page);
+
+ VM_BUG_ON(PageActive(page));
+ ClearPageUnevictable(page);
+ __dec_zone_state(zone, NR_UNEVICTABLE);
+ lruvec = mem_cgroup_lru_move_lists(zone, page,
+ LRU_UNEVICTABLE, lru);
+ list_move(&page->lru, &lruvec->lists[lru]);
+ __inc_zone_state(zone, NR_INACTIVE_ANON + lru);
+ pgrescued++;
+ }
+ }
+
+ if (zone) {
+ __count_vm_events(UNEVICTABLE_PGRESCUED, pgrescued);
+ __count_vm_events(UNEVICTABLE_PGSCANNED, pgscanned);
+ spin_unlock_irq(&zone->lru_lock);
+ }
+}
+#endif /* CONFIG_SHMEM */
+
+static void warn_scan_unevictable_pages(void)
+{
+ printk_once(KERN_WARNING
+ "%s: The scan_unevictable_pages sysctl/node-interface has been "
+ "disabled for lack of a legitimate use case. If you have "
+ "one, please send an email to linux-mm@kvack.org.\n",
+ current->comm);
+}
+
+/*
+ * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of
+ * all nodes' unevictable lists for evictable pages
+ */
+unsigned long scan_unevictable_pages;
+
+int scan_unevictable_handler(struct ctl_table *table, int write,
+ void __user *buffer,
+ size_t *length, loff_t *ppos)
+{
+ warn_scan_unevictable_pages();
+ proc_doulongvec_minmax(table, write, buffer, length, ppos);
+ scan_unevictable_pages = 0;
+ return 0;
+}
+
+#ifdef CONFIG_NUMA
+/*
+ * per node 'scan_unevictable_pages' attribute. On demand re-scan of
+ * a specified node's per zone unevictable lists for evictable pages.
+ */
+
+static ssize_t read_scan_unevictable_node(struct device *dev,
+ struct device_attribute *attr,
+ char *buf)
+{
+ warn_scan_unevictable_pages();
+ return sprintf(buf, "0\n"); /* always zero; should fit... */
+}
+
+static ssize_t write_scan_unevictable_node(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ warn_scan_unevictable_pages();
+ return 1;
+}
+
+
+static DEVICE_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR,
+ read_scan_unevictable_node,
+ write_scan_unevictable_node);
+
+int scan_unevictable_register_node(struct node *node)
+{
+ return device_create_file(&node->dev, &dev_attr_scan_unevictable_pages);
+}
+
+void scan_unevictable_unregister_node(struct node *node)
+{
+ device_remove_file(&node->dev, &dev_attr_scan_unevictable_pages);
+}
+#endif