[T106][ZXW-22]7520V3SCV2.01.01.02P42U09_VEC_V0.8_AP_VEC origin source commit
Change-Id: Ic6e05d89ecd62fc34f82b23dcf306c93764aec4b
diff --git a/ap/os/linux/linux-3.4.x/fs/dcache.c b/ap/os/linux/linux-3.4.x/fs/dcache.c
new file mode 100644
index 0000000..67a1377
--- /dev/null
+++ b/ap/os/linux/linux-3.4.x/fs/dcache.c
@@ -0,0 +1,3145 @@
+/*
+ * fs/dcache.c
+ *
+ * Complete reimplementation
+ * (C) 1997 Thomas Schoebel-Theuer,
+ * with heavy changes by Linus Torvalds
+ */
+
+/*
+ * Notes on the allocation strategy:
+ *
+ * The dcache is a master of the icache - whenever a dcache entry
+ * exists, the inode will always exist. "iput()" is done either when
+ * the dcache entry is deleted or garbage collected.
+ */
+
+#include <linux/syscalls.h>
+#include <linux/string.h>
+#include <linux/mm.h>
+#include <linux/fs.h>
+#include <linux/fsnotify.h>
+#include <linux/slab.h>
+#include <linux/init.h>
+#include <linux/hash.h>
+#include <linux/cache.h>
+#include <linux/export.h>
+#include <linux/mount.h>
+#include <linux/file.h>
+#include <asm/uaccess.h>
+#include <linux/security.h>
+#include <linux/seqlock.h>
+#include <linux/swap.h>
+#include <linux/bootmem.h>
+#include <linux/fs_struct.h>
+#include <linux/hardirq.h>
+#include <linux/bit_spinlock.h>
+#include <linux/rculist_bl.h>
+#include <linux/prefetch.h>
+#include <linux/ratelimit.h>
+#include <linux/delay.h>
+#include "internal.h"
+#include "mount.h"
+
+/*
+ * Usage:
+ * dcache->d_inode->i_lock protects:
+ * - i_dentry, d_u.d_alias, d_inode of aliases
+ * dcache_hash_bucket lock protects:
+ * - the dcache hash table
+ * s_anon bl list spinlock protects:
+ * - the s_anon list (see __d_drop)
+ * dcache_lru_lock protects:
+ * - the dcache lru lists and counters
+ * d_lock protects:
+ * - d_flags
+ * - d_name
+ * - d_lru
+ * - d_count
+ * - d_unhashed()
+ * - d_parent and d_subdirs
+ * - childrens' d_child and d_parent
+ * - d_u.d_alias, d_inode
+ *
+ * Ordering:
+ * dentry->d_inode->i_lock
+ * dentry->d_lock
+ * dcache_lru_lock
+ * dcache_hash_bucket lock
+ * s_anon lock
+ *
+ * If there is an ancestor relationship:
+ * dentry->d_parent->...->d_parent->d_lock
+ * ...
+ * dentry->d_parent->d_lock
+ * dentry->d_lock
+ *
+ * If no ancestor relationship:
+ * if (dentry1 < dentry2)
+ * dentry1->d_lock
+ * dentry2->d_lock
+ */
+int sysctl_vfs_cache_pressure __read_mostly = 100;
+EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure);
+
+static __cacheline_aligned_in_smp DEFINE_SPINLOCK(dcache_lru_lock);
+__cacheline_aligned_in_smp DEFINE_SEQLOCK(rename_lock);
+
+EXPORT_SYMBOL(rename_lock);
+
+static struct kmem_cache *dentry_cache __read_mostly;
+
+/*
+ * This is the single most critical data structure when it comes
+ * to the dcache: the hashtable for lookups. Somebody should try
+ * to make this good - I've just made it work.
+ *
+ * This hash-function tries to avoid losing too many bits of hash
+ * information, yet avoid using a prime hash-size or similar.
+ */
+#define D_HASHBITS d_hash_shift
+#define D_HASHMASK d_hash_mask
+
+static unsigned int d_hash_mask __read_mostly;
+static unsigned int d_hash_shift __read_mostly;
+
+static struct hlist_bl_head *dentry_hashtable __read_mostly;
+
+static inline struct hlist_bl_head *d_hash(const struct dentry *parent,
+ unsigned int hash)
+{
+ hash += (unsigned long) parent / L1_CACHE_BYTES;
+ hash = hash + (hash >> D_HASHBITS);
+ return dentry_hashtable + (hash & D_HASHMASK);
+}
+
+/* Statistics gathering. */
+struct dentry_stat_t dentry_stat = {
+ .age_limit = 45,
+};
+
+static DEFINE_PER_CPU(unsigned int, nr_dentry);
+
+#if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
+static int get_nr_dentry(void)
+{
+ int i;
+ int sum = 0;
+ for_each_possible_cpu(i)
+ sum += per_cpu(nr_dentry, i);
+ return sum < 0 ? 0 : sum;
+}
+
+int proc_nr_dentry(ctl_table *table, int write, void __user *buffer,
+ size_t *lenp, loff_t *ppos)
+{
+ dentry_stat.nr_dentry = get_nr_dentry();
+ return proc_dointvec(table, write, buffer, lenp, ppos);
+}
+#endif
+
+/*
+ * Compare 2 name strings, return 0 if they match, otherwise non-zero.
+ * The strings are both count bytes long, and count is non-zero.
+ */
+#ifdef CONFIG_DCACHE_WORD_ACCESS
+
+#include <asm/word-at-a-time.h>
+/*
+ * NOTE! 'cs' and 'scount' come from a dentry, so it has a
+ * aligned allocation for this particular component. We don't
+ * strictly need the load_unaligned_zeropad() safety, but it
+ * doesn't hurt either.
+ *
+ * In contrast, 'ct' and 'tcount' can be from a pathname, and do
+ * need the careful unaligned handling.
+ */
+static inline int dentry_cmp(const unsigned char *cs, size_t scount,
+ const unsigned char *ct, size_t tcount)
+{
+ unsigned long a,b,mask;
+
+ if (unlikely(scount != tcount))
+ return 1;
+
+ for (;;) {
+ a = load_unaligned_zeropad(cs);
+ b = load_unaligned_zeropad(ct);
+ if (tcount < sizeof(unsigned long))
+ break;
+ if (unlikely(a != b))
+ return 1;
+ cs += sizeof(unsigned long);
+ ct += sizeof(unsigned long);
+ tcount -= sizeof(unsigned long);
+ if (!tcount)
+ return 0;
+ }
+ mask = ~(~0ul << tcount*8);
+ return unlikely(!!((a ^ b) & mask));
+}
+
+#else
+
+static inline int dentry_cmp(const unsigned char *cs, size_t scount,
+ const unsigned char *ct, size_t tcount)
+{
+ if (scount != tcount)
+ return 1;
+
+ do {
+ if (*cs != *ct)
+ return 1;
+ cs++;
+ ct++;
+ tcount--;
+ } while (tcount);
+ return 0;
+}
+
+#endif
+
+static void __d_free(struct rcu_head *head)
+{
+ struct dentry *dentry = container_of(head, struct dentry, d_u.d_rcu);
+
+ if (dname_external(dentry))
+ kfree(dentry->d_name.name);
+ kmem_cache_free(dentry_cache, dentry);
+}
+
+/*
+ * no locks, please.
+ */
+static void d_free(struct dentry *dentry)
+{
+ WARN_ON(!list_empty(&dentry->d_u.d_alias));
+ BUG_ON(dentry->d_count);
+ this_cpu_dec(nr_dentry);
+ if (dentry->d_op && dentry->d_op->d_release)
+ dentry->d_op->d_release(dentry);
+
+ /* if dentry was never visible to RCU, immediate free is OK */
+ if (!(dentry->d_flags & DCACHE_RCUACCESS))
+ __d_free(&dentry->d_u.d_rcu);
+ else
+ call_rcu(&dentry->d_u.d_rcu, __d_free);
+}
+
+/**
+ * dentry_rcuwalk_barrier - invalidate in-progress rcu-walk lookups
+ * @dentry: the target dentry
+ * After this call, in-progress rcu-walk path lookup will fail. This
+ * should be called after unhashing, and after changing d_inode (if
+ * the dentry has not already been unhashed).
+ */
+static inline void dentry_rcuwalk_barrier(struct dentry *dentry)
+{
+ assert_spin_locked(&dentry->d_lock);
+ /* Go through a barrier */
+ write_seqcount_barrier(&dentry->d_seq);
+}
+
+/*
+ * Release the dentry's inode, using the filesystem
+ * d_iput() operation if defined. Dentry has no refcount
+ * and is unhashed.
+ */
+static void dentry_iput(struct dentry * dentry)
+ __releases(dentry->d_lock)
+ __releases(dentry->d_inode->i_lock)
+{
+ struct inode *inode = dentry->d_inode;
+ if (inode) {
+ dentry->d_inode = NULL;
+ list_del_init(&dentry->d_u.d_alias);
+ spin_unlock(&dentry->d_lock);
+ spin_unlock(&inode->i_lock);
+ if (!inode->i_nlink)
+ fsnotify_inoderemove(inode);
+ if (dentry->d_op && dentry->d_op->d_iput)
+ dentry->d_op->d_iput(dentry, inode);
+ else
+ iput(inode);
+ } else {
+ spin_unlock(&dentry->d_lock);
+ }
+}
+
+/*
+ * Release the dentry's inode, using the filesystem
+ * d_iput() operation if defined. dentry remains in-use.
+ */
+static void dentry_unlink_inode(struct dentry * dentry)
+ __releases(dentry->d_lock)
+ __releases(dentry->d_inode->i_lock)
+{
+ struct inode *inode = dentry->d_inode;
+ dentry->d_inode = NULL;
+ list_del_init(&dentry->d_u.d_alias);
+ dentry_rcuwalk_barrier(dentry);
+ spin_unlock(&dentry->d_lock);
+ spin_unlock(&inode->i_lock);
+ if (!inode->i_nlink)
+ fsnotify_inoderemove(inode);
+ if (dentry->d_op && dentry->d_op->d_iput)
+ dentry->d_op->d_iput(dentry, inode);
+ else
+ iput(inode);
+}
+
+/*
+ * dentry_lru_(add|del|prune|move_tail) must be called with d_lock held.
+ */
+static void dentry_lru_add(struct dentry *dentry)
+{
+ if (list_empty(&dentry->d_lru)) {
+ spin_lock(&dcache_lru_lock);
+ list_add(&dentry->d_lru, &dentry->d_sb->s_dentry_lru);
+ dentry->d_sb->s_nr_dentry_unused++;
+ dentry_stat.nr_unused++;
+ spin_unlock(&dcache_lru_lock);
+ }
+}
+
+static void __dentry_lru_del(struct dentry *dentry)
+{
+ list_del_init(&dentry->d_lru);
+ dentry->d_flags &= ~DCACHE_SHRINK_LIST;
+ dentry->d_sb->s_nr_dentry_unused--;
+ dentry_stat.nr_unused--;
+}
+
+/*
+ * Remove a dentry with references from the LRU.
+ */
+static void dentry_lru_del(struct dentry *dentry)
+{
+ if (!list_empty(&dentry->d_lru)) {
+ spin_lock(&dcache_lru_lock);
+ __dentry_lru_del(dentry);
+ spin_unlock(&dcache_lru_lock);
+ }
+}
+
+/*
+ * Remove a dentry that is unreferenced and about to be pruned
+ * (unhashed and destroyed) from the LRU, and inform the file system.
+ * This wrapper should be called _prior_ to unhashing a victim dentry.
+ */
+static void dentry_lru_prune(struct dentry *dentry)
+{
+ if (!list_empty(&dentry->d_lru)) {
+ if (dentry->d_flags & DCACHE_OP_PRUNE)
+ dentry->d_op->d_prune(dentry);
+
+ spin_lock(&dcache_lru_lock);
+ __dentry_lru_del(dentry);
+ spin_unlock(&dcache_lru_lock);
+ }
+}
+
+static void dentry_lru_move_list(struct dentry *dentry, struct list_head *list)
+{
+ spin_lock(&dcache_lru_lock);
+ if (list_empty(&dentry->d_lru)) {
+ list_add_tail(&dentry->d_lru, list);
+ dentry->d_sb->s_nr_dentry_unused++;
+ dentry_stat.nr_unused++;
+ } else {
+ list_move_tail(&dentry->d_lru, list);
+ }
+ spin_unlock(&dcache_lru_lock);
+}
+
+/**
+ * d_kill - kill dentry and return parent
+ * @dentry: dentry to kill
+ * @parent: parent dentry
+ *
+ * The dentry must already be unhashed and removed from the LRU.
+ *
+ * If this is the root of the dentry tree, return NULL.
+ *
+ * dentry->d_lock and parent->d_lock must be held by caller, and are dropped by
+ * d_kill.
+ */
+static struct dentry *d_kill(struct dentry *dentry, struct dentry *parent)
+ __releases(dentry->d_lock)
+ __releases(parent->d_lock)
+ __releases(dentry->d_inode->i_lock)
+{
+ __list_del_entry(&dentry->d_child);
+ /*
+ * Inform ascending readers that we are no longer attached to the
+ * dentry tree
+ */
+ dentry->d_flags |= DCACHE_DENTRY_KILLED;
+ if (parent)
+ spin_unlock(&parent->d_lock);
+ dentry_iput(dentry);
+ /*
+ * dentry_iput drops the locks, at which point nobody (except
+ * transient RCU lookups) can reach this dentry.
+ */
+ d_free(dentry);
+ return parent;
+}
+
+/*
+ * Unhash a dentry without inserting an RCU walk barrier or checking that
+ * dentry->d_lock is locked. The caller must take care of that, if
+ * appropriate.
+ */
+static void __d_shrink(struct dentry *dentry)
+{
+ if (!d_unhashed(dentry)) {
+ struct hlist_bl_head *b;
+ if (unlikely(dentry->d_flags & DCACHE_DISCONNECTED))
+ b = &dentry->d_sb->s_anon;
+ else
+ b = d_hash(dentry->d_parent, dentry->d_name.hash);
+
+ hlist_bl_lock(b);
+ __hlist_bl_del(&dentry->d_hash);
+ dentry->d_hash.pprev = NULL;
+ hlist_bl_unlock(b);
+ }
+}
+
+/**
+ * d_drop - drop a dentry
+ * @dentry: dentry to drop
+ *
+ * d_drop() unhashes the entry from the parent dentry hashes, so that it won't
+ * be found through a VFS lookup any more. Note that this is different from
+ * deleting the dentry - d_delete will try to mark the dentry negative if
+ * possible, giving a successful _negative_ lookup, while d_drop will
+ * just make the cache lookup fail.
+ *
+ * d_drop() is used mainly for stuff that wants to invalidate a dentry for some
+ * reason (NFS timeouts or autofs deletes).
+ *
+ * __d_drop requires dentry->d_lock.
+ */
+void __d_drop(struct dentry *dentry)
+{
+ if (!d_unhashed(dentry)) {
+ __d_shrink(dentry);
+ dentry_rcuwalk_barrier(dentry);
+ }
+}
+EXPORT_SYMBOL(__d_drop);
+
+void d_drop(struct dentry *dentry)
+{
+ spin_lock(&dentry->d_lock);
+ __d_drop(dentry);
+ spin_unlock(&dentry->d_lock);
+}
+EXPORT_SYMBOL(d_drop);
+
+/*
+ * d_clear_need_lookup - drop a dentry from cache and clear the need lookup flag
+ * @dentry: dentry to drop
+ *
+ * This is called when we do a lookup on a placeholder dentry that needed to be
+ * looked up. The dentry should have been hashed in order for it to be found by
+ * the lookup code, but now needs to be unhashed while we do the actual lookup
+ * and clear the DCACHE_NEED_LOOKUP flag.
+ */
+void d_clear_need_lookup(struct dentry *dentry)
+{
+ spin_lock(&dentry->d_lock);
+ __d_drop(dentry);
+ dentry->d_flags &= ~DCACHE_NEED_LOOKUP;
+ spin_unlock(&dentry->d_lock);
+}
+EXPORT_SYMBOL(d_clear_need_lookup);
+
+/*
+ * Finish off a dentry we've decided to kill.
+ * dentry->d_lock must be held, returns with it unlocked.
+ * If ref is non-zero, then decrement the refcount too.
+ * Returns dentry requiring refcount drop, or NULL if we're done.
+ */
+static inline struct dentry *dentry_kill(struct dentry *dentry, int ref)
+ __releases(dentry->d_lock)
+{
+ struct inode *inode;
+ struct dentry *parent;
+
+ inode = dentry->d_inode;
+ if (inode && !spin_trylock(&inode->i_lock)) {
+relock:
+ spin_unlock(&dentry->d_lock);
+ cpu_chill();
+ return dentry; /* try again with same dentry */
+ }
+ if (IS_ROOT(dentry))
+ parent = NULL;
+ else
+ parent = dentry->d_parent;
+ if (parent && !spin_trylock(&parent->d_lock)) {
+ if (inode)
+ spin_unlock(&inode->i_lock);
+ goto relock;
+ }
+
+ if (ref)
+ dentry->d_count--;
+ /*
+ * if dentry was on the d_lru list delete it from there.
+ * inform the fs via d_prune that this dentry is about to be
+ * unhashed and destroyed.
+ */
+ dentry_lru_prune(dentry);
+ /* if it was on the hash then remove it */
+ __d_drop(dentry);
+ return d_kill(dentry, parent);
+}
+
+/*
+ * This is dput
+ *
+ * This is complicated by the fact that we do not want to put
+ * dentries that are no longer on any hash chain on the unused
+ * list: we'd much rather just get rid of them immediately.
+ *
+ * However, that implies that we have to traverse the dentry
+ * tree upwards to the parents which might _also_ now be
+ * scheduled for deletion (it may have been only waiting for
+ * its last child to go away).
+ *
+ * This tail recursion is done by hand as we don't want to depend
+ * on the compiler to always get this right (gcc generally doesn't).
+ * Real recursion would eat up our stack space.
+ */
+
+/*
+ * dput - release a dentry
+ * @dentry: dentry to release
+ *
+ * Release a dentry. This will drop the usage count and if appropriate
+ * call the dentry unlink method as well as removing it from the queues and
+ * releasing its resources. If the parent dentries were scheduled for release
+ * they too may now get deleted.
+ */
+void dput(struct dentry *dentry)
+{
+ if (!dentry)
+ return;
+
+repeat:
+ if (dentry->d_count == 1)
+ might_sleep();
+ spin_lock(&dentry->d_lock);
+ BUG_ON(!dentry->d_count);
+ if (dentry->d_count > 1) {
+ dentry->d_count--;
+ spin_unlock(&dentry->d_lock);
+ return;
+ }
+
+ if (dentry->d_flags & DCACHE_OP_DELETE) {
+ if (dentry->d_op->d_delete(dentry))
+ goto kill_it;
+ }
+
+ /* Unreachable? Get rid of it */
+ if (d_unhashed(dentry))
+ goto kill_it;
+
+ /*
+ * If this dentry needs lookup, don't set the referenced flag so that it
+ * is more likely to be cleaned up by the dcache shrinker in case of
+ * memory pressure.
+ */
+ if (!d_need_lookup(dentry))
+ dentry->d_flags |= DCACHE_REFERENCED;
+ dentry_lru_add(dentry);
+
+ dentry->d_count--;
+ spin_unlock(&dentry->d_lock);
+ return;
+
+kill_it:
+ dentry = dentry_kill(dentry, 1);
+ if (dentry)
+ goto repeat;
+}
+EXPORT_SYMBOL(dput);
+
+/**
+ * d_invalidate - invalidate a dentry
+ * @dentry: dentry to invalidate
+ *
+ * Try to invalidate the dentry if it turns out to be
+ * possible. If there are other dentries that can be
+ * reached through this one we can't delete it and we
+ * return -EBUSY. On success we return 0.
+ *
+ * no dcache lock.
+ */
+
+int d_invalidate(struct dentry * dentry)
+{
+ /*
+ * If it's already been dropped, return OK.
+ */
+ spin_lock(&dentry->d_lock);
+ if (d_unhashed(dentry)) {
+ spin_unlock(&dentry->d_lock);
+ return 0;
+ }
+ /*
+ * Check whether to do a partial shrink_dcache
+ * to get rid of unused child entries.
+ */
+ if (!list_empty(&dentry->d_subdirs)) {
+ spin_unlock(&dentry->d_lock);
+ shrink_dcache_parent(dentry);
+ spin_lock(&dentry->d_lock);
+ }
+
+ /*
+ * Somebody else still using it?
+ *
+ * If it's a directory, we can't drop it
+ * for fear of somebody re-populating it
+ * with children (even though dropping it
+ * would make it unreachable from the root,
+ * we might still populate it if it was a
+ * working directory or similar).
+ * We also need to leave mountpoints alone,
+ * directory or not.
+ */
+ if (dentry->d_count > 1 && dentry->d_inode) {
+ if (S_ISDIR(dentry->d_inode->i_mode) || d_mountpoint(dentry)) {
+ spin_unlock(&dentry->d_lock);
+ return -EBUSY;
+ }
+ }
+
+ __d_drop(dentry);
+ spin_unlock(&dentry->d_lock);
+ return 0;
+}
+EXPORT_SYMBOL(d_invalidate);
+
+/* This must be called with d_lock held */
+static inline void __dget_dlock(struct dentry *dentry)
+{
+ dentry->d_count++;
+}
+
+static inline void __dget(struct dentry *dentry)
+{
+ spin_lock(&dentry->d_lock);
+ __dget_dlock(dentry);
+ spin_unlock(&dentry->d_lock);
+}
+
+struct dentry *dget_parent(struct dentry *dentry)
+{
+ struct dentry *ret;
+
+repeat:
+ /*
+ * Don't need rcu_dereference because we re-check it was correct under
+ * the lock.
+ */
+ rcu_read_lock();
+ ret = dentry->d_parent;
+ spin_lock(&ret->d_lock);
+ if (unlikely(ret != dentry->d_parent)) {
+ spin_unlock(&ret->d_lock);
+ rcu_read_unlock();
+ goto repeat;
+ }
+ rcu_read_unlock();
+ BUG_ON(!ret->d_count);
+ ret->d_count++;
+ spin_unlock(&ret->d_lock);
+ return ret;
+}
+EXPORT_SYMBOL(dget_parent);
+
+/**
+ * d_find_alias - grab a hashed alias of inode
+ * @inode: inode in question
+ * @want_discon: flag, used by d_splice_alias, to request
+ * that only a DISCONNECTED alias be returned.
+ *
+ * If inode has a hashed alias, or is a directory and has any alias,
+ * acquire the reference to alias and return it. Otherwise return NULL.
+ * Notice that if inode is a directory there can be only one alias and
+ * it can be unhashed only if it has no children, or if it is the root
+ * of a filesystem.
+ *
+ * If the inode has an IS_ROOT, DCACHE_DISCONNECTED alias, then prefer
+ * any other hashed alias over that one unless @want_discon is set,
+ * in which case only return an IS_ROOT, DCACHE_DISCONNECTED alias.
+ */
+static struct dentry *__d_find_alias(struct inode *inode, int want_discon)
+{
+ struct dentry *alias, *discon_alias;
+
+again:
+ discon_alias = NULL;
+ list_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) {
+ spin_lock(&alias->d_lock);
+ if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) {
+ if (IS_ROOT(alias) &&
+ (alias->d_flags & DCACHE_DISCONNECTED)) {
+ discon_alias = alias;
+ } else if (!want_discon) {
+ __dget_dlock(alias);
+ spin_unlock(&alias->d_lock);
+ return alias;
+ }
+ }
+ spin_unlock(&alias->d_lock);
+ }
+ if (discon_alias) {
+ alias = discon_alias;
+ spin_lock(&alias->d_lock);
+ if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) {
+ if (IS_ROOT(alias) &&
+ (alias->d_flags & DCACHE_DISCONNECTED)) {
+ __dget_dlock(alias);
+ spin_unlock(&alias->d_lock);
+ return alias;
+ }
+ }
+ spin_unlock(&alias->d_lock);
+ goto again;
+ }
+ return NULL;
+}
+
+struct dentry *d_find_alias(struct inode *inode)
+{
+ struct dentry *de = NULL;
+
+ if (!list_empty(&inode->i_dentry)) {
+ spin_lock(&inode->i_lock);
+ de = __d_find_alias(inode, 0);
+ spin_unlock(&inode->i_lock);
+ }
+ return de;
+}
+EXPORT_SYMBOL(d_find_alias);
+
+/*
+ * Try to kill dentries associated with this inode.
+ * WARNING: you must own a reference to inode.
+ */
+void d_prune_aliases(struct inode *inode)
+{
+ struct dentry *dentry;
+restart:
+ spin_lock(&inode->i_lock);
+ list_for_each_entry(dentry, &inode->i_dentry, d_u.d_alias) {
+ spin_lock(&dentry->d_lock);
+ if (!dentry->d_count) {
+ __dget_dlock(dentry);
+ __d_drop(dentry);
+ spin_unlock(&dentry->d_lock);
+ spin_unlock(&inode->i_lock);
+ dput(dentry);
+ goto restart;
+ }
+ spin_unlock(&dentry->d_lock);
+ }
+ spin_unlock(&inode->i_lock);
+}
+EXPORT_SYMBOL(d_prune_aliases);
+
+/*
+ * Try to throw away a dentry - free the inode, dput the parent.
+ * Requires dentry->d_lock is held, and dentry->d_count == 0.
+ * Releases dentry->d_lock.
+ *
+ * This may fail if locks cannot be acquired no problem, just try again.
+ */
+static void try_prune_one_dentry(struct dentry *dentry)
+ __releases(dentry->d_lock)
+{
+ struct dentry *parent;
+
+ parent = dentry_kill(dentry, 0);
+ /*
+ * If dentry_kill returns NULL, we have nothing more to do.
+ * if it returns the same dentry, trylocks failed. In either
+ * case, just loop again.
+ *
+ * Otherwise, we need to prune ancestors too. This is necessary
+ * to prevent quadratic behavior of shrink_dcache_parent(), but
+ * is also expected to be beneficial in reducing dentry cache
+ * fragmentation.
+ */
+ if (!parent)
+ return;
+ if (parent == dentry)
+ return;
+
+ /* Prune ancestors. */
+ dentry = parent;
+ while (dentry) {
+ spin_lock(&dentry->d_lock);
+ if (dentry->d_count > 1) {
+ dentry->d_count--;
+ spin_unlock(&dentry->d_lock);
+ return;
+ }
+ dentry = dentry_kill(dentry, 1);
+ }
+}
+
+static void shrink_dentry_list(struct list_head *list)
+{
+ struct dentry *dentry;
+
+ rcu_read_lock();
+ for (;;) {
+ dentry = list_entry_rcu(list->prev, struct dentry, d_lru);
+ if (&dentry->d_lru == list)
+ break; /* empty */
+ spin_lock(&dentry->d_lock);
+ if (dentry != list_entry(list->prev, struct dentry, d_lru)) {
+ spin_unlock(&dentry->d_lock);
+ continue;
+ }
+
+ /*
+ * We found an inuse dentry which was not removed from
+ * the LRU because of laziness during lookup. Do not free
+ * it - just keep it off the LRU list.
+ */
+ if (dentry->d_count) {
+ dentry_lru_del(dentry);
+ spin_unlock(&dentry->d_lock);
+ continue;
+ }
+
+ rcu_read_unlock();
+
+ try_prune_one_dentry(dentry);
+
+ rcu_read_lock();
+ }
+ rcu_read_unlock();
+}
+
+/**
+ * prune_dcache_sb - shrink the dcache
+ * @sb: superblock
+ * @count: number of entries to try to free
+ *
+ * Attempt to shrink the superblock dcache LRU by @count entries. This is
+ * done when we need more memory an called from the superblock shrinker
+ * function.
+ *
+ * This function may fail to free any resources if all the dentries are in
+ * use.
+ */
+void prune_dcache_sb(struct super_block *sb, int count)
+{
+ struct dentry *dentry;
+ LIST_HEAD(referenced);
+ LIST_HEAD(tmp);
+
+relock:
+ spin_lock(&dcache_lru_lock);
+ while (!list_empty(&sb->s_dentry_lru)) {
+ dentry = list_entry(sb->s_dentry_lru.prev,
+ struct dentry, d_lru);
+ BUG_ON(dentry->d_sb != sb);
+
+ if (!spin_trylock(&dentry->d_lock)) {
+ spin_unlock(&dcache_lru_lock);
+ cpu_chill();
+ goto relock;
+ }
+
+ if (dentry->d_flags & DCACHE_REFERENCED) {
+ dentry->d_flags &= ~DCACHE_REFERENCED;
+ list_move(&dentry->d_lru, &referenced);
+ spin_unlock(&dentry->d_lock);
+ } else {
+ list_move_tail(&dentry->d_lru, &tmp);
+ dentry->d_flags |= DCACHE_SHRINK_LIST;
+ spin_unlock(&dentry->d_lock);
+ if (!--count)
+ break;
+ }
+ cond_resched_lock(&dcache_lru_lock);
+ }
+ if (!list_empty(&referenced))
+ list_splice(&referenced, &sb->s_dentry_lru);
+ spin_unlock(&dcache_lru_lock);
+
+ shrink_dentry_list(&tmp);
+}
+
+/**
+ * shrink_dcache_sb - shrink dcache for a superblock
+ * @sb: superblock
+ *
+ * Shrink the dcache for the specified super block. This is used to free
+ * the dcache before unmounting a file system.
+ */
+void shrink_dcache_sb(struct super_block *sb)
+{
+ LIST_HEAD(tmp);
+
+ spin_lock(&dcache_lru_lock);
+ while (!list_empty(&sb->s_dentry_lru)) {
+ list_splice_init(&sb->s_dentry_lru, &tmp);
+ spin_unlock(&dcache_lru_lock);
+ shrink_dentry_list(&tmp);
+ spin_lock(&dcache_lru_lock);
+ }
+ spin_unlock(&dcache_lru_lock);
+}
+EXPORT_SYMBOL(shrink_dcache_sb);
+
+/*
+ * destroy a single subtree of dentries for unmount
+ * - see the comments on shrink_dcache_for_umount() for a description of the
+ * locking
+ */
+static void shrink_dcache_for_umount_subtree(struct dentry *dentry)
+{
+ struct dentry *parent;
+
+ BUG_ON(!IS_ROOT(dentry));
+
+ for (;;) {
+ /* descend to the first leaf in the current subtree */
+ while (!list_empty(&dentry->d_subdirs))
+ dentry = list_entry(dentry->d_subdirs.next,
+ struct dentry, d_child);
+
+ /* consume the dentries from this leaf up through its parents
+ * until we find one with children or run out altogether */
+ do {
+ struct inode *inode;
+
+ /*
+ * remove the dentry from the lru, and inform
+ * the fs that this dentry is about to be
+ * unhashed and destroyed.
+ */
+ dentry_lru_prune(dentry);
+ __d_shrink(dentry);
+
+ if (dentry->d_count != 0) {
+ printk(KERN_ERR
+ "BUG: Dentry %p{i=%lx,n=%s}"
+ " still in use (%d)"
+ " [unmount of %s %s]\n",
+ dentry,
+ dentry->d_inode ?
+ dentry->d_inode->i_ino : 0UL,
+ dentry->d_name.name,
+ dentry->d_count,
+ dentry->d_sb->s_type->name,
+ dentry->d_sb->s_id);
+ BUG();
+ }
+
+ if (IS_ROOT(dentry)) {
+ parent = NULL;
+ list_del(&dentry->d_child);
+ } else {
+ parent = dentry->d_parent;
+ parent->d_count--;
+ list_del(&dentry->d_child);
+ }
+
+ inode = dentry->d_inode;
+ if (inode) {
+ dentry->d_inode = NULL;
+ list_del_init(&dentry->d_u.d_alias);
+ if (dentry->d_op && dentry->d_op->d_iput)
+ dentry->d_op->d_iput(dentry, inode);
+ else
+ iput(inode);
+ }
+
+ d_free(dentry);
+
+ /* finished when we fall off the top of the tree,
+ * otherwise we ascend to the parent and move to the
+ * next sibling if there is one */
+ if (!parent)
+ return;
+ dentry = parent;
+ } while (list_empty(&dentry->d_subdirs));
+
+ dentry = list_entry(dentry->d_subdirs.next,
+ struct dentry, d_child);
+ }
+}
+
+/*
+ * destroy the dentries attached to a superblock on unmounting
+ * - we don't need to use dentry->d_lock because:
+ * - the superblock is detached from all mountings and open files, so the
+ * dentry trees will not be rearranged by the VFS
+ * - s_umount is write-locked, so the memory pressure shrinker will ignore
+ * any dentries belonging to this superblock that it comes across
+ * - the filesystem itself is no longer permitted to rearrange the dentries
+ * in this superblock
+ */
+void shrink_dcache_for_umount(struct super_block *sb)
+{
+ struct dentry *dentry;
+
+ if (down_read_trylock(&sb->s_umount))
+ BUG();
+
+ dentry = sb->s_root;
+ sb->s_root = NULL;
+ dentry->d_count--;
+ shrink_dcache_for_umount_subtree(dentry);
+
+ while (!hlist_bl_empty(&sb->s_anon)) {
+ dentry = hlist_bl_entry(hlist_bl_first(&sb->s_anon), struct dentry, d_hash);
+ shrink_dcache_for_umount_subtree(dentry);
+ }
+}
+
+
+/*
+ * Search for at least 1 mount point in the dentry's subdirs.
+ * We descend to the next level whenever the d_subdirs
+ * list is non-empty and continue searching.
+ */
+
+/**
+ * have_submounts - check for mounts over a dentry
+ * @parent: dentry to check.
+ *
+ * Return true if the parent or its subdirectories contain
+ * a mount point
+ */
+int have_submounts(struct dentry *parent)
+{
+ struct dentry *this_parent;
+ struct list_head *next;
+ unsigned seq;
+ int locked = 0;
+
+ seq = read_seqbegin(&rename_lock);
+again:
+ this_parent = parent;
+
+ if (d_mountpoint(parent))
+ goto positive;
+ spin_lock(&this_parent->d_lock);
+repeat:
+ next = this_parent->d_subdirs.next;
+resume:
+ while (next != &this_parent->d_subdirs) {
+ struct list_head *tmp = next;
+ struct dentry *dentry = list_entry(tmp, struct dentry, d_child);
+ next = tmp->next;
+
+ spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
+ /* Have we found a mount point ? */
+ if (d_mountpoint(dentry)) {
+ spin_unlock(&dentry->d_lock);
+ spin_unlock(&this_parent->d_lock);
+ goto positive;
+ }
+ if (!list_empty(&dentry->d_subdirs)) {
+ spin_unlock(&this_parent->d_lock);
+ spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_);
+ this_parent = dentry;
+ spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
+ goto repeat;
+ }
+ spin_unlock(&dentry->d_lock);
+ }
+ /*
+ * All done at this level ... ascend and resume the search.
+ */
+ rcu_read_lock();
+ascend:
+ if (this_parent != parent) {
+ struct dentry *child = this_parent;
+ this_parent = child->d_parent;
+
+ spin_unlock(&child->d_lock);
+ spin_lock(&this_parent->d_lock);
+
+ /* might go back up the wrong parent if we have had a rename */
+ if (!locked && read_seqretry(&rename_lock, seq))
+ goto rename_retry;
+ next = child->d_child.next;
+ while (unlikely(child->d_flags & DCACHE_DENTRY_KILLED)) {
+ if (next == &this_parent->d_subdirs)
+ goto ascend;
+ child = list_entry(next, struct dentry, d_child);
+ next = next->next;
+ }
+ rcu_read_unlock();
+ goto resume;
+ }
+ if (!locked && read_seqretry(&rename_lock, seq))
+ goto rename_retry;
+ spin_unlock(&this_parent->d_lock);
+ rcu_read_unlock();
+ if (locked)
+ write_sequnlock(&rename_lock);
+ return 0; /* No mount points found in tree */
+positive:
+ if (!locked && read_seqretry(&rename_lock, seq))
+ goto rename_retry_unlocked;
+ if (locked)
+ write_sequnlock(&rename_lock);
+ return 1;
+
+rename_retry:
+ spin_unlock(&this_parent->d_lock);
+ rcu_read_unlock();
+ if (locked)
+ goto again;
+rename_retry_unlocked:
+ locked = 1;
+ write_seqlock(&rename_lock);
+ goto again;
+}
+EXPORT_SYMBOL(have_submounts);
+
+/*
+ * Search the dentry child list for the specified parent,
+ * and move any unused dentries to the end of the unused
+ * list for prune_dcache(). We descend to the next level
+ * whenever the d_subdirs list is non-empty and continue
+ * searching.
+ *
+ * It returns zero iff there are no unused children,
+ * otherwise it returns the number of children moved to
+ * the end of the unused list. This may not be the total
+ * number of unused children, because select_parent can
+ * drop the lock and return early due to latency
+ * constraints.
+ */
+static int select_parent(struct dentry *parent, struct list_head *dispose)
+{
+ struct dentry *this_parent;
+ struct list_head *next;
+ unsigned seq;
+ int found = 0;
+ int locked = 0;
+
+ seq = read_seqbegin(&rename_lock);
+again:
+ this_parent = parent;
+ spin_lock(&this_parent->d_lock);
+repeat:
+ next = this_parent->d_subdirs.next;
+resume:
+ while (next != &this_parent->d_subdirs) {
+ struct list_head *tmp = next;
+ struct dentry *dentry = list_entry(tmp, struct dentry, d_child);
+ next = tmp->next;
+
+ spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
+
+ /*
+ * move only zero ref count dentries to the dispose list.
+ *
+ * Those which are presently on the shrink list, being processed
+ * by shrink_dentry_list(), shouldn't be moved. Otherwise the
+ * loop in shrink_dcache_parent() might not make any progress
+ * and loop forever.
+ */
+ if (dentry->d_count) {
+ dentry_lru_del(dentry);
+ } else if (!(dentry->d_flags & DCACHE_SHRINK_LIST)) {
+ dentry_lru_move_list(dentry, dispose);
+ dentry->d_flags |= DCACHE_SHRINK_LIST;
+ found++;
+ }
+ /*
+ * We can return to the caller if we have found some (this
+ * ensures forward progress). We'll be coming back to find
+ * the rest.
+ */
+ if (found && need_resched()) {
+ spin_unlock(&dentry->d_lock);
+ rcu_read_lock();
+ goto out;
+ }
+
+ /*
+ * Descend a level if the d_subdirs list is non-empty.
+ */
+ if (!list_empty(&dentry->d_subdirs)) {
+ spin_unlock(&this_parent->d_lock);
+ spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_);
+ this_parent = dentry;
+ spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
+ goto repeat;
+ }
+
+ spin_unlock(&dentry->d_lock);
+ }
+ /*
+ * All done at this level ... ascend and resume the search.
+ */
+ rcu_read_lock();
+ascend:
+ if (this_parent != parent) {
+ struct dentry *child = this_parent;
+ this_parent = child->d_parent;
+
+ spin_unlock(&child->d_lock);
+ spin_lock(&this_parent->d_lock);
+
+ /* might go back up the wrong parent if we have had a rename */
+ if (!locked && read_seqretry(&rename_lock, seq))
+ goto rename_retry;
+ /* go into the first sibling still alive */
+ do {
+ next = child->d_child.next;
+ if (next == &this_parent->d_subdirs)
+ goto ascend;
+ child = list_entry(next, struct dentry, d_child);
+ } while (unlikely(child->d_flags & DCACHE_DENTRY_KILLED));
+ rcu_read_unlock();
+ goto resume;
+ }
+out:
+ if (!locked && read_seqretry(&rename_lock, seq))
+ goto rename_retry;
+ spin_unlock(&this_parent->d_lock);
+ rcu_read_unlock();
+ if (locked)
+ write_sequnlock(&rename_lock);
+ return found;
+
+rename_retry:
+ spin_unlock(&this_parent->d_lock);
+ rcu_read_unlock();
+ if (found)
+ return found;
+ if (locked)
+ goto again;
+ locked = 1;
+ write_seqlock(&rename_lock);
+ goto again;
+}
+
+/**
+ * shrink_dcache_parent - prune dcache
+ * @parent: parent of entries to prune
+ *
+ * Prune the dcache to remove unused children of the parent dentry.
+ */
+void shrink_dcache_parent(struct dentry * parent)
+{
+ LIST_HEAD(dispose);
+ int found;
+
+ while ((found = select_parent(parent, &dispose)) != 0) {
+ shrink_dentry_list(&dispose);
+ cond_resched();
+ }
+}
+EXPORT_SYMBOL(shrink_dcache_parent);
+
+/**
+ * __d_alloc - allocate a dcache entry
+ * @sb: filesystem it will belong to
+ * @name: qstr of the name
+ *
+ * Allocates a dentry. It returns %NULL if there is insufficient memory
+ * available. On a success the dentry is returned. The name passed in is
+ * copied and the copy passed in may be reused after this call.
+ */
+
+struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name)
+{
+ struct dentry *dentry;
+ char *dname;
+
+ dentry = kmem_cache_alloc(dentry_cache, GFP_KERNEL);
+ if (!dentry)
+ return NULL;
+
+ if (name->len > DNAME_INLINE_LEN-1) {
+ dname = kmalloc(name->len + 1, GFP_KERNEL);
+ if (!dname) {
+ kmem_cache_free(dentry_cache, dentry);
+ return NULL;
+ }
+ } else {
+ dname = dentry->d_iname;
+ }
+ dentry->d_name.name = dname;
+
+ dentry->d_name.len = name->len;
+ dentry->d_name.hash = name->hash;
+ memcpy(dname, name->name, name->len);
+ dname[name->len] = 0;
+
+ dentry->d_count = 1;
+ dentry->d_flags = 0;
+ spin_lock_init(&dentry->d_lock);
+ seqcount_init(&dentry->d_seq);
+ dentry->d_inode = NULL;
+ dentry->d_parent = dentry;
+ dentry->d_sb = sb;
+ dentry->d_op = NULL;
+ dentry->d_fsdata = NULL;
+ INIT_HLIST_BL_NODE(&dentry->d_hash);
+ INIT_LIST_HEAD(&dentry->d_lru);
+ INIT_LIST_HEAD(&dentry->d_subdirs);
+ INIT_LIST_HEAD(&dentry->d_u.d_alias);
+ INIT_LIST_HEAD(&dentry->d_child);
+ d_set_d_op(dentry, dentry->d_sb->s_d_op);
+
+ this_cpu_inc(nr_dentry);
+
+ return dentry;
+}
+
+/**
+ * d_alloc - allocate a dcache entry
+ * @parent: parent of entry to allocate
+ * @name: qstr of the name
+ *
+ * Allocates a dentry. It returns %NULL if there is insufficient memory
+ * available. On a success the dentry is returned. The name passed in is
+ * copied and the copy passed in may be reused after this call.
+ */
+struct dentry *d_alloc(struct dentry * parent, const struct qstr *name)
+{
+ struct dentry *dentry = __d_alloc(parent->d_sb, name);
+ if (!dentry)
+ return NULL;
+
+ spin_lock(&parent->d_lock);
+ /*
+ * don't need child lock because it is not subject
+ * to concurrency here
+ */
+ __dget_dlock(parent);
+ dentry->d_parent = parent;
+ list_add(&dentry->d_child, &parent->d_subdirs);
+ spin_unlock(&parent->d_lock);
+
+ return dentry;
+}
+EXPORT_SYMBOL(d_alloc);
+
+struct dentry *d_alloc_pseudo(struct super_block *sb, const struct qstr *name)
+{
+ struct dentry *dentry = __d_alloc(sb, name);
+ if (dentry)
+ dentry->d_flags |= DCACHE_DISCONNECTED;
+ return dentry;
+}
+EXPORT_SYMBOL(d_alloc_pseudo);
+
+struct dentry *d_alloc_name(struct dentry *parent, const char *name)
+{
+ struct qstr q;
+
+ q.name = name;
+ q.len = strlen(name);
+ q.hash = full_name_hash(q.name, q.len);
+ return d_alloc(parent, &q);
+}
+EXPORT_SYMBOL(d_alloc_name);
+
+void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op)
+{
+ WARN_ON_ONCE(dentry->d_op);
+ WARN_ON_ONCE(dentry->d_flags & (DCACHE_OP_HASH |
+ DCACHE_OP_COMPARE |
+ DCACHE_OP_REVALIDATE |
+ DCACHE_OP_DELETE ));
+ dentry->d_op = op;
+ if (!op)
+ return;
+ if (op->d_hash)
+ dentry->d_flags |= DCACHE_OP_HASH;
+ if (op->d_compare)
+ dentry->d_flags |= DCACHE_OP_COMPARE;
+ if (op->d_revalidate)
+ dentry->d_flags |= DCACHE_OP_REVALIDATE;
+ if (op->d_delete)
+ dentry->d_flags |= DCACHE_OP_DELETE;
+ if (op->d_prune)
+ dentry->d_flags |= DCACHE_OP_PRUNE;
+
+}
+EXPORT_SYMBOL(d_set_d_op);
+
+static void __d_instantiate(struct dentry *dentry, struct inode *inode)
+{
+ spin_lock(&dentry->d_lock);
+ if (inode) {
+ if (unlikely(IS_AUTOMOUNT(inode)))
+ dentry->d_flags |= DCACHE_NEED_AUTOMOUNT;
+ list_add(&dentry->d_u.d_alias, &inode->i_dentry);
+ }
+ dentry->d_inode = inode;
+ dentry_rcuwalk_barrier(dentry);
+ spin_unlock(&dentry->d_lock);
+ fsnotify_d_instantiate(dentry, inode);
+}
+
+/**
+ * d_instantiate - fill in inode information for a dentry
+ * @entry: dentry to complete
+ * @inode: inode to attach to this dentry
+ *
+ * Fill in inode information in the entry.
+ *
+ * This turns negative dentries into productive full members
+ * of society.
+ *
+ * NOTE! This assumes that the inode count has been incremented
+ * (or otherwise set) by the caller to indicate that it is now
+ * in use by the dcache.
+ */
+
+void d_instantiate(struct dentry *entry, struct inode * inode)
+{
+ BUG_ON(!list_empty(&entry->d_u.d_alias));
+ if (inode)
+ spin_lock(&inode->i_lock);
+ __d_instantiate(entry, inode);
+ if (inode)
+ spin_unlock(&inode->i_lock);
+ security_d_instantiate(entry, inode);
+}
+EXPORT_SYMBOL(d_instantiate);
+
+/**
+ * d_instantiate_unique - instantiate a non-aliased dentry
+ * @entry: dentry to instantiate
+ * @inode: inode to attach to this dentry
+ *
+ * Fill in inode information in the entry. On success, it returns NULL.
+ * If an unhashed alias of "entry" already exists, then we return the
+ * aliased dentry instead and drop one reference to inode.
+ *
+ * Note that in order to avoid conflicts with rename() etc, the caller
+ * had better be holding the parent directory semaphore.
+ *
+ * This also assumes that the inode count has been incremented
+ * (or otherwise set) by the caller to indicate that it is now
+ * in use by the dcache.
+ */
+static struct dentry *__d_instantiate_unique(struct dentry *entry,
+ struct inode *inode)
+{
+ struct dentry *alias;
+ int len = entry->d_name.len;
+ const char *name = entry->d_name.name;
+ unsigned int hash = entry->d_name.hash;
+
+ if (!inode) {
+ __d_instantiate(entry, NULL);
+ return NULL;
+ }
+
+ list_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) {
+ struct qstr *qstr = &alias->d_name;
+
+ /*
+ * Don't need alias->d_lock here, because aliases with
+ * d_parent == entry->d_parent are not subject to name or
+ * parent changes, because the parent inode i_mutex is held.
+ */
+ if (qstr->hash != hash)
+ continue;
+ if (alias->d_parent != entry->d_parent)
+ continue;
+ if (dentry_cmp(qstr->name, qstr->len, name, len))
+ continue;
+ __dget(alias);
+ return alias;
+ }
+
+ __d_instantiate(entry, inode);
+ return NULL;
+}
+
+struct dentry *d_instantiate_unique(struct dentry *entry, struct inode *inode)
+{
+ struct dentry *result;
+
+ BUG_ON(!list_empty(&entry->d_u.d_alias));
+
+ if (inode)
+ spin_lock(&inode->i_lock);
+ result = __d_instantiate_unique(entry, inode);
+ if (inode)
+ spin_unlock(&inode->i_lock);
+
+ if (!result) {
+ security_d_instantiate(entry, inode);
+ return NULL;
+ }
+
+ BUG_ON(!d_unhashed(result));
+ iput(inode);
+ return result;
+}
+
+EXPORT_SYMBOL(d_instantiate_unique);
+
+struct dentry *d_make_root(struct inode *root_inode)
+{
+ struct dentry *res = NULL;
+
+ if (root_inode) {
+ static const struct qstr name = { .name = "/", .len = 1 };
+
+ res = __d_alloc(root_inode->i_sb, &name);
+ if (res)
+ d_instantiate(res, root_inode);
+ else
+ iput(root_inode);
+ }
+ return res;
+}
+EXPORT_SYMBOL(d_make_root);
+
+static struct dentry * __d_find_any_alias(struct inode *inode)
+{
+ struct dentry *alias;
+
+ if (list_empty(&inode->i_dentry))
+ return NULL;
+ alias = list_first_entry(&inode->i_dentry, struct dentry, d_u.d_alias);
+ __dget(alias);
+ return alias;
+}
+
+/**
+ * d_find_any_alias - find any alias for a given inode
+ * @inode: inode to find an alias for
+ *
+ * If any aliases exist for the given inode, take and return a
+ * reference for one of them. If no aliases exist, return %NULL.
+ */
+struct dentry *d_find_any_alias(struct inode *inode)
+{
+ struct dentry *de;
+
+ spin_lock(&inode->i_lock);
+ de = __d_find_any_alias(inode);
+ spin_unlock(&inode->i_lock);
+ return de;
+}
+EXPORT_SYMBOL(d_find_any_alias);
+
+/**
+ * d_obtain_alias - find or allocate a dentry for a given inode
+ * @inode: inode to allocate the dentry for
+ *
+ * Obtain a dentry for an inode resulting from NFS filehandle conversion or
+ * similar open by handle operations. The returned dentry may be anonymous,
+ * or may have a full name (if the inode was already in the cache).
+ *
+ * When called on a directory inode, we must ensure that the inode only ever
+ * has one dentry. If a dentry is found, that is returned instead of
+ * allocating a new one.
+ *
+ * On successful return, the reference to the inode has been transferred
+ * to the dentry. In case of an error the reference on the inode is released.
+ * To make it easier to use in export operations a %NULL or IS_ERR inode may
+ * be passed in and will be the error will be propagate to the return value,
+ * with a %NULL @inode replaced by ERR_PTR(-ESTALE).
+ */
+struct dentry *d_obtain_alias(struct inode *inode)
+{
+ static const struct qstr anonstring = { .name = "/", .len = 1 };
+ struct dentry *tmp;
+ struct dentry *res;
+
+ if (!inode)
+ return ERR_PTR(-ESTALE);
+ if (IS_ERR(inode))
+ return ERR_CAST(inode);
+
+ res = d_find_any_alias(inode);
+ if (res)
+ goto out_iput;
+
+ tmp = __d_alloc(inode->i_sb, &anonstring);
+ if (!tmp) {
+ res = ERR_PTR(-ENOMEM);
+ goto out_iput;
+ }
+
+ spin_lock(&inode->i_lock);
+ res = __d_find_any_alias(inode);
+ if (res) {
+ spin_unlock(&inode->i_lock);
+ dput(tmp);
+ goto out_iput;
+ }
+
+ /* attach a disconnected dentry */
+ spin_lock(&tmp->d_lock);
+ tmp->d_inode = inode;
+ tmp->d_flags |= DCACHE_DISCONNECTED;
+ list_add(&tmp->d_u.d_alias, &inode->i_dentry);
+ hlist_bl_lock(&tmp->d_sb->s_anon);
+ hlist_bl_add_head(&tmp->d_hash, &tmp->d_sb->s_anon);
+ hlist_bl_unlock(&tmp->d_sb->s_anon);
+ spin_unlock(&tmp->d_lock);
+ spin_unlock(&inode->i_lock);
+ security_d_instantiate(tmp, inode);
+
+ return tmp;
+
+ out_iput:
+ if (res && !IS_ERR(res))
+ security_d_instantiate(res, inode);
+ iput(inode);
+ return res;
+}
+EXPORT_SYMBOL(d_obtain_alias);
+
+/**
+ * d_splice_alias - splice a disconnected dentry into the tree if one exists
+ * @inode: the inode which may have a disconnected dentry
+ * @dentry: a negative dentry which we want to point to the inode.
+ *
+ * If inode is a directory and has a 'disconnected' dentry (i.e. IS_ROOT and
+ * DCACHE_DISCONNECTED), then d_move that in place of the given dentry
+ * and return it, else simply d_add the inode to the dentry and return NULL.
+ *
+ * This is needed in the lookup routine of any filesystem that is exportable
+ * (via knfsd) so that we can build dcache paths to directories effectively.
+ *
+ * If a dentry was found and moved, then it is returned. Otherwise NULL
+ * is returned. This matches the expected return value of ->lookup.
+ *
+ */
+struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
+{
+ struct dentry *new = NULL;
+
+ if (IS_ERR(inode))
+ return ERR_CAST(inode);
+
+ if (inode && S_ISDIR(inode->i_mode)) {
+ spin_lock(&inode->i_lock);
+ new = __d_find_alias(inode, 1);
+ if (new) {
+ BUG_ON(!(new->d_flags & DCACHE_DISCONNECTED));
+ spin_unlock(&inode->i_lock);
+ security_d_instantiate(new, inode);
+ d_move(new, dentry);
+ iput(inode);
+ } else {
+ /* already taking inode->i_lock, so d_add() by hand */
+ __d_instantiate(dentry, inode);
+ spin_unlock(&inode->i_lock);
+ security_d_instantiate(dentry, inode);
+ d_rehash(dentry);
+ }
+ } else
+ d_add(dentry, inode);
+ return new;
+}
+EXPORT_SYMBOL(d_splice_alias);
+
+/**
+ * d_add_ci - lookup or allocate new dentry with case-exact name
+ * @inode: the inode case-insensitive lookup has found
+ * @dentry: the negative dentry that was passed to the parent's lookup func
+ * @name: the case-exact name to be associated with the returned dentry
+ *
+ * This is to avoid filling the dcache with case-insensitive names to the
+ * same inode, only the actual correct case is stored in the dcache for
+ * case-insensitive filesystems.
+ *
+ * For a case-insensitive lookup match and if the the case-exact dentry
+ * already exists in in the dcache, use it and return it.
+ *
+ * If no entry exists with the exact case name, allocate new dentry with
+ * the exact case, and return the spliced entry.
+ */
+struct dentry *d_add_ci(struct dentry *dentry, struct inode *inode,
+ struct qstr *name)
+{
+ int error;
+ struct dentry *found;
+ struct dentry *new;
+
+ /*
+ * First check if a dentry matching the name already exists,
+ * if not go ahead and create it now.
+ */
+ found = d_hash_and_lookup(dentry->d_parent, name);
+ if (!found) {
+ new = d_alloc(dentry->d_parent, name);
+ if (!new) {
+ error = -ENOMEM;
+ goto err_out;
+ }
+
+ found = d_splice_alias(inode, new);
+ if (found) {
+ dput(new);
+ return found;
+ }
+ return new;
+ }
+
+ /*
+ * If a matching dentry exists, and it's not negative use it.
+ *
+ * Decrement the reference count to balance the iget() done
+ * earlier on.
+ */
+ if (found->d_inode) {
+ if (unlikely(found->d_inode != inode)) {
+ /* This can't happen because bad inodes are unhashed. */
+ BUG_ON(!is_bad_inode(inode));
+ BUG_ON(!is_bad_inode(found->d_inode));
+ }
+ iput(inode);
+ return found;
+ }
+
+ /*
+ * We are going to instantiate this dentry, unhash it and clear the
+ * lookup flag so we can do that.
+ */
+ if (unlikely(d_need_lookup(found)))
+ d_clear_need_lookup(found);
+
+ /*
+ * Negative dentry: instantiate it unless the inode is a directory and
+ * already has a dentry.
+ */
+ new = d_splice_alias(inode, found);
+ if (new) {
+ dput(found);
+ found = new;
+ }
+ return found;
+
+err_out:
+ iput(inode);
+ return ERR_PTR(error);
+}
+EXPORT_SYMBOL(d_add_ci);
+
+/**
+ * __d_lookup_rcu - search for a dentry (racy, store-free)
+ * @parent: parent dentry
+ * @name: qstr of name we wish to find
+ * @seqp: returns d_seq value at the point where the dentry was found
+ * @inode: returns dentry->d_inode when the inode was found valid.
+ * Returns: dentry, or NULL
+ *
+ * __d_lookup_rcu is the dcache lookup function for rcu-walk name
+ * resolution (store-free path walking) design described in
+ * Documentation/filesystems/path-lookup.txt.
+ *
+ * This is not to be used outside core vfs.
+ *
+ * __d_lookup_rcu must only be used in rcu-walk mode, ie. with vfsmount lock
+ * held, and rcu_read_lock held. The returned dentry must not be stored into
+ * without taking d_lock and checking d_seq sequence count against @seq
+ * returned here.
+ *
+ * A refcount may be taken on the found dentry with the __d_rcu_to_refcount
+ * function.
+ *
+ * Alternatively, __d_lookup_rcu may be called again to look up the child of
+ * the returned dentry, so long as its parent's seqlock is checked after the
+ * child is looked up. Thus, an interlocking stepping of sequence lock checks
+ * is formed, giving integrity down the path walk.
+ */
+struct dentry *__d_lookup_rcu(const struct dentry *parent,
+ const struct qstr *name,
+ unsigned *seqp, struct inode **inode)
+{
+ unsigned int len = name->len;
+ unsigned int hash = name->hash;
+ const unsigned char *str = name->name;
+ struct hlist_bl_head *b = d_hash(parent, hash);
+ struct hlist_bl_node *node;
+ struct dentry *dentry;
+
+ /*
+ * Note: There is significant duplication with __d_lookup_rcu which is
+ * required to prevent single threaded performance regressions
+ * especially on architectures where smp_rmb (in seqcounts) are costly.
+ * Keep the two functions in sync.
+ */
+
+ /*
+ * The hash list is protected using RCU.
+ *
+ * Carefully use d_seq when comparing a candidate dentry, to avoid
+ * races with d_move().
+ *
+ * It is possible that concurrent renames can mess up our list
+ * walk here and result in missing our dentry, resulting in the
+ * false-negative result. d_lookup() protects against concurrent
+ * renames using rename_lock seqlock.
+ *
+ * See Documentation/filesystems/path-lookup.txt for more details.
+ */
+ hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
+ unsigned seq;
+ struct inode *i;
+ const char *tname;
+ int tlen;
+
+ if (dentry->d_name.hash != hash)
+ continue;
+
+seqretry:
+ seq = read_seqcount_begin(&dentry->d_seq);
+ if (dentry->d_parent != parent)
+ continue;
+ if (d_unhashed(dentry))
+ continue;
+ tlen = dentry->d_name.len;
+ tname = dentry->d_name.name;
+ i = dentry->d_inode;
+ prefetch(tname);
+ /*
+ * This seqcount check is required to ensure name and
+ * len are loaded atomically, so as not to walk off the
+ * edge of memory when walking. If we could load this
+ * atomically some other way, we could drop this check.
+ */
+ if (read_seqcount_retry(&dentry->d_seq, seq))
+ goto seqretry;
+ if (unlikely(parent->d_flags & DCACHE_OP_COMPARE)) {
+ if (parent->d_op->d_compare(parent, *inode,
+ dentry, i,
+ tlen, tname, name))
+ continue;
+ } else {
+ if (dentry_cmp(tname, tlen, str, len))
+ continue;
+ }
+ /*
+ * No extra seqcount check is required after the name
+ * compare. The caller must perform a seqcount check in
+ * order to do anything useful with the returned dentry
+ * anyway.
+ */
+ *seqp = seq;
+ *inode = i;
+ return dentry;
+ }
+ return NULL;
+}
+
+/**
+ * d_lookup - search for a dentry
+ * @parent: parent dentry
+ * @name: qstr of name we wish to find
+ * Returns: dentry, or NULL
+ *
+ * d_lookup searches the children of the parent dentry for the name in
+ * question. If the dentry is found its reference count is incremented and the
+ * dentry is returned. The caller must use dput to free the entry when it has
+ * finished using it. %NULL is returned if the dentry does not exist.
+ */
+struct dentry *d_lookup(struct dentry *parent, struct qstr *name)
+{
+ struct dentry *dentry;
+ unsigned seq;
+
+ do {
+ seq = read_seqbegin(&rename_lock);
+ dentry = __d_lookup(parent, name);
+ if (dentry)
+ break;
+ } while (read_seqretry(&rename_lock, seq));
+ return dentry;
+}
+EXPORT_SYMBOL(d_lookup);
+
+/**
+ * __d_lookup - search for a dentry (racy)
+ * @parent: parent dentry
+ * @name: qstr of name we wish to find
+ * Returns: dentry, or NULL
+ *
+ * __d_lookup is like d_lookup, however it may (rarely) return a
+ * false-negative result due to unrelated rename activity.
+ *
+ * __d_lookup is slightly faster by avoiding rename_lock read seqlock,
+ * however it must be used carefully, eg. with a following d_lookup in
+ * the case of failure.
+ *
+ * __d_lookup callers must be commented.
+ */
+struct dentry *__d_lookup(struct dentry *parent, struct qstr *name)
+{
+ unsigned int len = name->len;
+ unsigned int hash = name->hash;
+ const unsigned char *str = name->name;
+ struct hlist_bl_head *b = d_hash(parent, hash);
+ struct hlist_bl_node *node;
+ struct dentry *found = NULL;
+ struct dentry *dentry;
+
+ /*
+ * Note: There is significant duplication with __d_lookup_rcu which is
+ * required to prevent single threaded performance regressions
+ * especially on architectures where smp_rmb (in seqcounts) are costly.
+ * Keep the two functions in sync.
+ */
+
+ /*
+ * The hash list is protected using RCU.
+ *
+ * Take d_lock when comparing a candidate dentry, to avoid races
+ * with d_move().
+ *
+ * It is possible that concurrent renames can mess up our list
+ * walk here and result in missing our dentry, resulting in the
+ * false-negative result. d_lookup() protects against concurrent
+ * renames using rename_lock seqlock.
+ *
+ * See Documentation/filesystems/path-lookup.txt for more details.
+ */
+ rcu_read_lock();
+
+ hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
+ const char *tname;
+ int tlen;
+
+ if (dentry->d_name.hash != hash)
+ continue;
+
+ spin_lock(&dentry->d_lock);
+ if (dentry->d_parent != parent)
+ goto next;
+ if (d_unhashed(dentry))
+ goto next;
+
+ /*
+ * It is safe to compare names since d_move() cannot
+ * change the qstr (protected by d_lock).
+ */
+ tlen = dentry->d_name.len;
+ tname = dentry->d_name.name;
+ if (parent->d_flags & DCACHE_OP_COMPARE) {
+ if (parent->d_op->d_compare(parent, parent->d_inode,
+ dentry, dentry->d_inode,
+ tlen, tname, name))
+ goto next;
+ } else {
+ if (dentry_cmp(tname, tlen, str, len))
+ goto next;
+ }
+
+ dentry->d_count++;
+ found = dentry;
+ spin_unlock(&dentry->d_lock);
+ break;
+next:
+ spin_unlock(&dentry->d_lock);
+ }
+ rcu_read_unlock();
+
+ return found;
+}
+
+/**
+ * d_hash_and_lookup - hash the qstr then search for a dentry
+ * @dir: Directory to search in
+ * @name: qstr of name we wish to find
+ *
+ * On hash failure or on lookup failure NULL is returned.
+ */
+struct dentry *d_hash_and_lookup(struct dentry *dir, struct qstr *name)
+{
+ struct dentry *dentry = NULL;
+
+ /*
+ * Check for a fs-specific hash function. Note that we must
+ * calculate the standard hash first, as the d_op->d_hash()
+ * routine may choose to leave the hash value unchanged.
+ */
+ name->hash = full_name_hash(name->name, name->len);
+ if (dir->d_flags & DCACHE_OP_HASH) {
+ if (dir->d_op->d_hash(dir, dir->d_inode, name) < 0)
+ goto out;
+ }
+ dentry = d_lookup(dir, name);
+out:
+ return dentry;
+}
+
+/**
+ * d_validate - verify dentry provided from insecure source (deprecated)
+ * @dentry: The dentry alleged to be valid child of @dparent
+ * @dparent: The parent dentry (known to be valid)
+ *
+ * An insecure source has sent us a dentry, here we verify it and dget() it.
+ * This is used by ncpfs in its readdir implementation.
+ * Zero is returned in the dentry is invalid.
+ *
+ * This function is slow for big directories, and deprecated, do not use it.
+ */
+int d_validate(struct dentry *dentry, struct dentry *dparent)
+{
+ struct dentry *child;
+
+ spin_lock(&dparent->d_lock);
+ list_for_each_entry(child, &dparent->d_subdirs, d_child) {
+ if (dentry == child) {
+ spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
+ __dget_dlock(dentry);
+ spin_unlock(&dentry->d_lock);
+ spin_unlock(&dparent->d_lock);
+ return 1;
+ }
+ }
+ spin_unlock(&dparent->d_lock);
+
+ return 0;
+}
+EXPORT_SYMBOL(d_validate);
+
+/*
+ * When a file is deleted, we have two options:
+ * - turn this dentry into a negative dentry
+ * - unhash this dentry and free it.
+ *
+ * Usually, we want to just turn this into
+ * a negative dentry, but if anybody else is
+ * currently using the dentry or the inode
+ * we can't do that and we fall back on removing
+ * it from the hash queues and waiting for
+ * it to be deleted later when it has no users
+ */
+
+/**
+ * d_delete - delete a dentry
+ * @dentry: The dentry to delete
+ *
+ * Turn the dentry into a negative dentry if possible, otherwise
+ * remove it from the hash queues so it can be deleted later
+ */
+
+void d_delete(struct dentry * dentry)
+{
+ struct inode *inode;
+ int isdir = 0;
+ /*
+ * Are we the only user?
+ */
+again:
+ spin_lock(&dentry->d_lock);
+ inode = dentry->d_inode;
+ isdir = S_ISDIR(inode->i_mode);
+ if (dentry->d_count == 1) {
+ if (inode && !spin_trylock(&inode->i_lock)) {
+ spin_unlock(&dentry->d_lock);
+ cpu_chill();
+ goto again;
+ }
+ dentry->d_flags &= ~DCACHE_CANT_MOUNT;
+ dentry_unlink_inode(dentry);
+ fsnotify_nameremove(dentry, isdir);
+ return;
+ }
+
+ if (!d_unhashed(dentry))
+ __d_drop(dentry);
+
+ spin_unlock(&dentry->d_lock);
+
+ fsnotify_nameremove(dentry, isdir);
+}
+EXPORT_SYMBOL(d_delete);
+
+static void __d_rehash(struct dentry * entry, struct hlist_bl_head *b)
+{
+ BUG_ON(!d_unhashed(entry));
+ hlist_bl_lock(b);
+ entry->d_flags |= DCACHE_RCUACCESS;
+ hlist_bl_add_head_rcu(&entry->d_hash, b);
+ hlist_bl_unlock(b);
+}
+
+static void _d_rehash(struct dentry * entry)
+{
+ __d_rehash(entry, d_hash(entry->d_parent, entry->d_name.hash));
+}
+
+/**
+ * d_rehash - add an entry back to the hash
+ * @entry: dentry to add to the hash
+ *
+ * Adds a dentry to the hash according to its name.
+ */
+
+void d_rehash(struct dentry * entry)
+{
+ spin_lock(&entry->d_lock);
+ _d_rehash(entry);
+ spin_unlock(&entry->d_lock);
+}
+EXPORT_SYMBOL(d_rehash);
+
+/**
+ * dentry_update_name_case - update case insensitive dentry with a new name
+ * @dentry: dentry to be updated
+ * @name: new name
+ *
+ * Update a case insensitive dentry with new case of name.
+ *
+ * dentry must have been returned by d_lookup with name @name. Old and new
+ * name lengths must match (ie. no d_compare which allows mismatched name
+ * lengths).
+ *
+ * Parent inode i_mutex must be held over d_lookup and into this call (to
+ * keep renames and concurrent inserts, and readdir(2) away).
+ */
+void dentry_update_name_case(struct dentry *dentry, struct qstr *name)
+{
+ BUG_ON(!mutex_is_locked(&dentry->d_parent->d_inode->i_mutex));
+ BUG_ON(dentry->d_name.len != name->len); /* d_lookup gives this */
+
+ spin_lock(&dentry->d_lock);
+ write_seqcount_begin(&dentry->d_seq);
+ memcpy((unsigned char *)dentry->d_name.name, name->name, name->len);
+ write_seqcount_end(&dentry->d_seq);
+ spin_unlock(&dentry->d_lock);
+}
+EXPORT_SYMBOL(dentry_update_name_case);
+
+static void switch_names(struct dentry *dentry, struct dentry *target)
+{
+ if (dname_external(target)) {
+ if (dname_external(dentry)) {
+ /*
+ * Both external: swap the pointers
+ */
+ swap(target->d_name.name, dentry->d_name.name);
+ } else {
+ /*
+ * dentry:internal, target:external. Steal target's
+ * storage and make target internal.
+ */
+ memcpy(target->d_iname, dentry->d_name.name,
+ dentry->d_name.len + 1);
+ dentry->d_name.name = target->d_name.name;
+ target->d_name.name = target->d_iname;
+ }
+ } else {
+ if (dname_external(dentry)) {
+ /*
+ * dentry:external, target:internal. Give dentry's
+ * storage to target and make dentry internal
+ */
+ memcpy(dentry->d_iname, target->d_name.name,
+ target->d_name.len + 1);
+ target->d_name.name = dentry->d_name.name;
+ dentry->d_name.name = dentry->d_iname;
+ } else {
+ /*
+ * Both are internal. Just copy target to dentry
+ */
+ memcpy(dentry->d_iname, target->d_name.name,
+ target->d_name.len + 1);
+ dentry->d_name.len = target->d_name.len;
+ return;
+ }
+ }
+ swap(dentry->d_name.len, target->d_name.len);
+}
+
+static void dentry_lock_for_move(struct dentry *dentry, struct dentry *target)
+{
+ /*
+ * XXXX: do we really need to take target->d_lock?
+ */
+ if (IS_ROOT(dentry) || dentry->d_parent == target->d_parent)
+ spin_lock(&target->d_parent->d_lock);
+ else {
+ if (d_ancestor(dentry->d_parent, target->d_parent)) {
+ spin_lock(&dentry->d_parent->d_lock);
+ spin_lock_nested(&target->d_parent->d_lock,
+ DENTRY_D_LOCK_NESTED);
+ } else {
+ spin_lock(&target->d_parent->d_lock);
+ spin_lock_nested(&dentry->d_parent->d_lock,
+ DENTRY_D_LOCK_NESTED);
+ }
+ }
+ if (target < dentry) {
+ spin_lock_nested(&target->d_lock, 2);
+ spin_lock_nested(&dentry->d_lock, 3);
+ } else {
+ spin_lock_nested(&dentry->d_lock, 2);
+ spin_lock_nested(&target->d_lock, 3);
+ }
+}
+
+static void dentry_unlock_parents_for_move(struct dentry *dentry,
+ struct dentry *target)
+{
+ if (target->d_parent != dentry->d_parent)
+ spin_unlock(&dentry->d_parent->d_lock);
+ if (target->d_parent != target)
+ spin_unlock(&target->d_parent->d_lock);
+}
+
+/*
+ * When switching names, the actual string doesn't strictly have to
+ * be preserved in the target - because we're dropping the target
+ * anyway. As such, we can just do a simple memcpy() to copy over
+ * the new name before we switch.
+ *
+ * Note that we have to be a lot more careful about getting the hash
+ * switched - we have to switch the hash value properly even if it
+ * then no longer matches the actual (corrupted) string of the target.
+ * The hash value has to match the hash queue that the dentry is on..
+ */
+/*
+ * __d_move - move a dentry
+ * @dentry: entry to move
+ * @target: new dentry
+ *
+ * Update the dcache to reflect the move of a file name. Negative
+ * dcache entries should not be moved in this way. Caller must hold
+ * rename_lock, the i_mutex of the source and target directories,
+ * and the sb->s_vfs_rename_mutex if they differ. See lock_rename().
+ */
+static void __d_move(struct dentry * dentry, struct dentry * target)
+{
+ if (!dentry->d_inode)
+ printk(KERN_WARNING "VFS: moving negative dcache entry\n");
+
+ BUG_ON(d_ancestor(dentry, target));
+ BUG_ON(d_ancestor(target, dentry));
+
+ dentry_lock_for_move(dentry, target);
+
+ write_seqcount_begin(&dentry->d_seq);
+ write_seqcount_begin(&target->d_seq);
+
+ /* __d_drop does write_seqcount_barrier, but they're OK to nest. */
+
+ /*
+ * Move the dentry to the target hash queue. Don't bother checking
+ * for the same hash queue because of how unlikely it is.
+ */
+ __d_drop(dentry);
+ __d_rehash(dentry, d_hash(target->d_parent, target->d_name.hash));
+
+ /* Unhash the target: dput() will then get rid of it */
+ __d_drop(target);
+
+ list_del(&dentry->d_child);
+ list_del(&target->d_child);
+
+ /* Switch the names.. */
+ switch_names(dentry, target);
+ swap(dentry->d_name.hash, target->d_name.hash);
+
+ /* ... and switch the parents */
+ if (IS_ROOT(dentry)) {
+ dentry->d_parent = target->d_parent;
+ target->d_parent = target;
+ INIT_LIST_HEAD(&target->d_child);
+ } else {
+ swap(dentry->d_parent, target->d_parent);
+
+ /* And add them back to the (new) parent lists */
+ list_add(&target->d_child, &target->d_parent->d_subdirs);
+ }
+
+ list_add(&dentry->d_child, &dentry->d_parent->d_subdirs);
+
+ write_seqcount_end(&target->d_seq);
+ write_seqcount_end(&dentry->d_seq);
+
+ dentry_unlock_parents_for_move(dentry, target);
+ spin_unlock(&target->d_lock);
+ fsnotify_d_move(dentry);
+ spin_unlock(&dentry->d_lock);
+}
+
+/*
+ * d_move - move a dentry
+ * @dentry: entry to move
+ * @target: new dentry
+ *
+ * Update the dcache to reflect the move of a file name. Negative
+ * dcache entries should not be moved in this way. See the locking
+ * requirements for __d_move.
+ */
+void d_move(struct dentry *dentry, struct dentry *target)
+{
+ write_seqlock(&rename_lock);
+ __d_move(dentry, target);
+ write_sequnlock(&rename_lock);
+}
+EXPORT_SYMBOL(d_move);
+
+/**
+ * d_ancestor - search for an ancestor
+ * @p1: ancestor dentry
+ * @p2: child dentry
+ *
+ * Returns the ancestor dentry of p2 which is a child of p1, if p1 is
+ * an ancestor of p2, else NULL.
+ */
+struct dentry *d_ancestor(struct dentry *p1, struct dentry *p2)
+{
+ struct dentry *p;
+
+ for (p = p2; !IS_ROOT(p); p = p->d_parent) {
+ if (p->d_parent == p1)
+ return p;
+ }
+ return NULL;
+}
+
+/*
+ * This helper attempts to cope with remotely renamed directories
+ *
+ * It assumes that the caller is already holding
+ * dentry->d_parent->d_inode->i_mutex, inode->i_lock and rename_lock
+ *
+ * Note: If ever the locking in lock_rename() changes, then please
+ * remember to update this too...
+ */
+static struct dentry *__d_unalias(struct inode *inode,
+ struct dentry *dentry, struct dentry *alias)
+{
+ struct mutex *m1 = NULL, *m2 = NULL;
+ struct dentry *ret;
+
+ /* If alias and dentry share a parent, then no extra locks required */
+ if (alias->d_parent == dentry->d_parent)
+ goto out_unalias;
+
+ /* See lock_rename() */
+ ret = ERR_PTR(-EBUSY);
+ if (!mutex_trylock(&dentry->d_sb->s_vfs_rename_mutex))
+ goto out_err;
+ m1 = &dentry->d_sb->s_vfs_rename_mutex;
+ if (!mutex_trylock(&alias->d_parent->d_inode->i_mutex))
+ goto out_err;
+ m2 = &alias->d_parent->d_inode->i_mutex;
+out_unalias:
+ __d_move(alias, dentry);
+ ret = alias;
+out_err:
+ spin_unlock(&inode->i_lock);
+ if (m2)
+ mutex_unlock(m2);
+ if (m1)
+ mutex_unlock(m1);
+ return ret;
+}
+
+/*
+ * Prepare an anonymous dentry for life in the superblock's dentry tree as a
+ * named dentry in place of the dentry to be replaced.
+ * returns with anon->d_lock held!
+ */
+static void __d_materialise_dentry(struct dentry *dentry, struct dentry *anon)
+{
+ struct dentry *dparent, *aparent;
+
+ dentry_lock_for_move(anon, dentry);
+
+ write_seqcount_begin(&dentry->d_seq);
+ write_seqcount_begin(&anon->d_seq);
+
+ dparent = dentry->d_parent;
+ aparent = anon->d_parent;
+
+ switch_names(dentry, anon);
+ swap(dentry->d_name.hash, anon->d_name.hash);
+
+ dentry->d_parent = (aparent == anon) ? dentry : aparent;
+ list_del(&dentry->d_child);
+ if (!IS_ROOT(dentry))
+ list_add(&dentry->d_child, &dentry->d_parent->d_subdirs);
+ else
+ INIT_LIST_HEAD(&dentry->d_child);
+
+ anon->d_parent = (dparent == dentry) ? anon : dparent;
+ list_del(&anon->d_child);
+ if (!IS_ROOT(anon))
+ list_add(&anon->d_child, &anon->d_parent->d_subdirs);
+ else
+ INIT_LIST_HEAD(&anon->d_child);
+
+ write_seqcount_end(&dentry->d_seq);
+ write_seqcount_end(&anon->d_seq);
+
+ dentry_unlock_parents_for_move(anon, dentry);
+ spin_unlock(&dentry->d_lock);
+
+ /* anon->d_lock still locked, returns locked */
+ anon->d_flags &= ~DCACHE_DISCONNECTED;
+}
+
+/**
+ * d_materialise_unique - introduce an inode into the tree
+ * @dentry: candidate dentry
+ * @inode: inode to bind to the dentry, to which aliases may be attached
+ *
+ * Introduces an dentry into the tree, substituting an extant disconnected
+ * root directory alias in its place if there is one. Caller must hold the
+ * i_mutex of the parent directory.
+ */
+struct dentry *d_materialise_unique(struct dentry *dentry, struct inode *inode)
+{
+ struct dentry *actual;
+
+ BUG_ON(!d_unhashed(dentry));
+
+ if (!inode) {
+ actual = dentry;
+ __d_instantiate(dentry, NULL);
+ d_rehash(actual);
+ goto out_nolock;
+ }
+
+ spin_lock(&inode->i_lock);
+
+ if (S_ISDIR(inode->i_mode)) {
+ struct dentry *alias;
+
+ /* Does an aliased dentry already exist? */
+ alias = __d_find_alias(inode, 0);
+ if (alias) {
+ actual = alias;
+ write_seqlock(&rename_lock);
+
+ if (d_ancestor(alias, dentry)) {
+ /* Check for loops */
+ actual = ERR_PTR(-ELOOP);
+ spin_unlock(&inode->i_lock);
+ } else if (IS_ROOT(alias)) {
+ /* Is this an anonymous mountpoint that we
+ * could splice into our tree? */
+ __d_materialise_dentry(dentry, alias);
+ write_sequnlock(&rename_lock);
+ __d_drop(alias);
+ goto found;
+ } else {
+ /* Nope, but we must(!) avoid directory
+ * aliasing. This drops inode->i_lock */
+ actual = __d_unalias(inode, dentry, alias);
+ }
+ write_sequnlock(&rename_lock);
+ if (IS_ERR(actual)) {
+ if (PTR_ERR(actual) == -ELOOP)
+ pr_warn_ratelimited(
+ "VFS: Lookup of '%s' in %s %s"
+ " would have caused loop\n",
+ dentry->d_name.name,
+ inode->i_sb->s_type->name,
+ inode->i_sb->s_id);
+ dput(alias);
+ }
+ goto out_nolock;
+ }
+ }
+
+ /* Add a unique reference */
+ actual = __d_instantiate_unique(dentry, inode);
+ if (!actual)
+ actual = dentry;
+ else
+ BUG_ON(!d_unhashed(actual));
+
+ spin_lock(&actual->d_lock);
+found:
+ _d_rehash(actual);
+ spin_unlock(&actual->d_lock);
+ spin_unlock(&inode->i_lock);
+out_nolock:
+ if (actual == dentry) {
+ security_d_instantiate(dentry, inode);
+ return NULL;
+ }
+
+ iput(inode);
+ return actual;
+}
+EXPORT_SYMBOL_GPL(d_materialise_unique);
+
+static int prepend(char **buffer, int *buflen, const char *str, int namelen)
+{
+ *buflen -= namelen;
+ if (*buflen < 0)
+ return -ENAMETOOLONG;
+ *buffer -= namelen;
+ memcpy(*buffer, str, namelen);
+ return 0;
+}
+
+static int prepend_name(char **buffer, int *buflen, struct qstr *name)
+{
+ return prepend(buffer, buflen, name->name, name->len);
+}
+
+/**
+ * prepend_path - Prepend path string to a buffer
+ * @path: the dentry/vfsmount to report
+ * @root: root vfsmnt/dentry
+ * @buffer: pointer to the end of the buffer
+ * @buflen: pointer to buffer length
+ *
+ * Caller holds the rename_lock.
+ */
+static int prepend_path(const struct path *path,
+ const struct path *root,
+ char **buffer, int *buflen)
+{
+ struct dentry *dentry = path->dentry;
+ struct vfsmount *vfsmnt = path->mnt;
+ struct mount *mnt = real_mount(vfsmnt);
+ char *orig_buffer = *buffer;
+ int orig_len = *buflen;
+ bool slash = false;
+ int error = 0;
+
+ while (dentry != root->dentry || vfsmnt != root->mnt) {
+ struct dentry * parent;
+
+ if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
+ /* Escaped? */
+ if (dentry != vfsmnt->mnt_root) {
+ *buffer = orig_buffer;
+ *buflen = orig_len;
+ slash = false;
+ error = 3;
+ goto global_root;
+ }
+ /* Global root? */
+ if (!mnt_has_parent(mnt))
+ goto global_root;
+ dentry = mnt->mnt_mountpoint;
+ mnt = mnt->mnt_parent;
+ vfsmnt = &mnt->mnt;
+ continue;
+ }
+ parent = dentry->d_parent;
+ prefetch(parent);
+ spin_lock(&dentry->d_lock);
+ error = prepend_name(buffer, buflen, &dentry->d_name);
+ spin_unlock(&dentry->d_lock);
+ if (!error)
+ error = prepend(buffer, buflen, "/", 1);
+ if (error)
+ break;
+
+ slash = true;
+ dentry = parent;
+ }
+
+ if (!error && !slash)
+ error = prepend(buffer, buflen, "/", 1);
+
+ return error;
+
+global_root:
+ /*
+ * Filesystems needing to implement special "root names"
+ * should do so with ->d_dname()
+ */
+ if (IS_ROOT(dentry) &&
+ (dentry->d_name.len != 1 || dentry->d_name.name[0] != '/')) {
+ WARN(1, "Root dentry has weird name <%.*s>\n",
+ (int) dentry->d_name.len, dentry->d_name.name);
+ }
+ if (!slash)
+ error = prepend(buffer, buflen, "/", 1);
+ if (!error)
+ error = real_mount(vfsmnt)->mnt_ns ? 1 : 2;
+ return error;
+}
+
+/**
+ * __d_path - return the path of a dentry
+ * @path: the dentry/vfsmount to report
+ * @root: root vfsmnt/dentry
+ * @buf: buffer to return value in
+ * @buflen: buffer length
+ *
+ * Convert a dentry into an ASCII path name.
+ *
+ * Returns a pointer into the buffer or an error code if the
+ * path was too long.
+ *
+ * "buflen" should be positive.
+ *
+ * If the path is not reachable from the supplied root, return %NULL.
+ */
+char *__d_path(const struct path *path,
+ const struct path *root,
+ char *buf, int buflen)
+{
+ char *res = buf + buflen;
+ int error;
+
+ prepend(&res, &buflen, "\0", 1);
+ br_read_lock(vfsmount_lock);
+ write_seqlock(&rename_lock);
+ error = prepend_path(path, root, &res, &buflen);
+ write_sequnlock(&rename_lock);
+ br_read_unlock(vfsmount_lock);
+
+ if (error < 0)
+ return ERR_PTR(error);
+ if (error > 0)
+ return NULL;
+ return res;
+}
+
+char *d_absolute_path(const struct path *path,
+ char *buf, int buflen)
+{
+ struct path root = {};
+ char *res = buf + buflen;
+ int error;
+
+ prepend(&res, &buflen, "\0", 1);
+ br_read_lock(vfsmount_lock);
+ write_seqlock(&rename_lock);
+ error = prepend_path(path, &root, &res, &buflen);
+ write_sequnlock(&rename_lock);
+ br_read_unlock(vfsmount_lock);
+
+ if (error > 1)
+ error = -EINVAL;
+ if (error < 0)
+ return ERR_PTR(error);
+ return res;
+}
+
+/*
+ * same as __d_path but appends "(deleted)" for unlinked files.
+ */
+static int path_with_deleted(const struct path *path,
+ const struct path *root,
+ char **buf, int *buflen)
+{
+ prepend(buf, buflen, "\0", 1);
+ if (d_unlinked(path->dentry)) {
+ int error = prepend(buf, buflen, " (deleted)", 10);
+ if (error)
+ return error;
+ }
+
+ return prepend_path(path, root, buf, buflen);
+}
+
+static int prepend_unreachable(char **buffer, int *buflen)
+{
+ return prepend(buffer, buflen, "(unreachable)", 13);
+}
+
+/**
+ * d_path - return the path of a dentry
+ * @path: path to report
+ * @buf: buffer to return value in
+ * @buflen: buffer length
+ *
+ * Convert a dentry into an ASCII path name. If the entry has been deleted
+ * the string " (deleted)" is appended. Note that this is ambiguous.
+ *
+ * Returns a pointer into the buffer or an error code if the path was
+ * too long. Note: Callers should use the returned pointer, not the passed
+ * in buffer, to use the name! The implementation often starts at an offset
+ * into the buffer, and may leave 0 bytes at the start.
+ *
+ * "buflen" should be positive.
+ */
+char *d_path(const struct path *path, char *buf, int buflen)
+{
+ char *res = buf + buflen;
+ struct path root;
+ int error;
+
+ /*
+ * We have various synthetic filesystems that never get mounted. On
+ * these filesystems dentries are never used for lookup purposes, and
+ * thus don't need to be hashed. They also don't need a name until a
+ * user wants to identify the object in /proc/pid/fd/. The little hack
+ * below allows us to generate a name for these objects on demand:
+ */
+ if (path->dentry->d_op && path->dentry->d_op->d_dname)
+ return path->dentry->d_op->d_dname(path->dentry, buf, buflen);
+
+ get_fs_root(current->fs, &root);
+ br_read_lock(vfsmount_lock);
+ write_seqlock(&rename_lock);
+ error = path_with_deleted(path, &root, &res, &buflen);
+ write_sequnlock(&rename_lock);
+ br_read_unlock(vfsmount_lock);
+ if (error < 0)
+ res = ERR_PTR(error);
+ path_put(&root);
+ return res;
+}
+EXPORT_SYMBOL(d_path);
+
+/**
+ * d_path_with_unreachable - return the path of a dentry
+ * @path: path to report
+ * @buf: buffer to return value in
+ * @buflen: buffer length
+ *
+ * The difference from d_path() is that this prepends "(unreachable)"
+ * to paths which are unreachable from the current process' root.
+ */
+char *d_path_with_unreachable(const struct path *path, char *buf, int buflen)
+{
+ char *res = buf + buflen;
+ struct path root;
+ int error;
+
+ if (path->dentry->d_op && path->dentry->d_op->d_dname)
+ return path->dentry->d_op->d_dname(path->dentry, buf, buflen);
+
+ get_fs_root(current->fs, &root);
+ write_seqlock(&rename_lock);
+ error = path_with_deleted(path, &root, &res, &buflen);
+ if (error > 0)
+ error = prepend_unreachable(&res, &buflen);
+ write_sequnlock(&rename_lock);
+ path_put(&root);
+ if (error)
+ res = ERR_PTR(error);
+
+ return res;
+}
+
+/*
+ * Helper function for dentry_operations.d_dname() members
+ */
+char *dynamic_dname(struct dentry *dentry, char *buffer, int buflen,
+ const char *fmt, ...)
+{
+ va_list args;
+ char temp[64];
+ int sz;
+
+ va_start(args, fmt);
+ sz = vsnprintf(temp, sizeof(temp), fmt, args) + 1;
+ va_end(args);
+
+ if (sz > sizeof(temp) || sz > buflen)
+ return ERR_PTR(-ENAMETOOLONG);
+
+ buffer += buflen - sz;
+ return memcpy(buffer, temp, sz);
+}
+
+/*
+ * Write full pathname from the root of the filesystem into the buffer.
+ */
+static char *__dentry_path(struct dentry *dentry, char *buf, int buflen)
+{
+ char *end = buf + buflen;
+ char *retval;
+
+ prepend(&end, &buflen, "\0", 1);
+ if (buflen < 1)
+ goto Elong;
+ /* Get '/' right */
+ retval = end-1;
+ *retval = '/';
+
+ while (!IS_ROOT(dentry)) {
+ struct dentry *parent = dentry->d_parent;
+ int error;
+
+ prefetch(parent);
+ spin_lock(&dentry->d_lock);
+ error = prepend_name(&end, &buflen, &dentry->d_name);
+ spin_unlock(&dentry->d_lock);
+ if (error != 0 || prepend(&end, &buflen, "/", 1) != 0)
+ goto Elong;
+
+ retval = end;
+ dentry = parent;
+ }
+ return retval;
+Elong:
+ return ERR_PTR(-ENAMETOOLONG);
+}
+
+char *dentry_path_raw(struct dentry *dentry, char *buf, int buflen)
+{
+ char *retval;
+
+ write_seqlock(&rename_lock);
+ retval = __dentry_path(dentry, buf, buflen);
+ write_sequnlock(&rename_lock);
+
+ return retval;
+}
+EXPORT_SYMBOL(dentry_path_raw);
+
+char *dentry_path(struct dentry *dentry, char *buf, int buflen)
+{
+ char *p = NULL;
+ char *retval;
+
+ write_seqlock(&rename_lock);
+ if (d_unlinked(dentry)) {
+ p = buf + buflen;
+ if (prepend(&p, &buflen, "//deleted", 10) != 0)
+ goto Elong;
+ buflen++;
+ }
+ retval = __dentry_path(dentry, buf, buflen);
+ write_sequnlock(&rename_lock);
+ if (!IS_ERR(retval) && p)
+ *p = '/'; /* restore '/' overriden with '\0' */
+ return retval;
+Elong:
+ return ERR_PTR(-ENAMETOOLONG);
+}
+
+/*
+ * NOTE! The user-level library version returns a
+ * character pointer. The kernel system call just
+ * returns the length of the buffer filled (which
+ * includes the ending '\0' character), or a negative
+ * error value. So libc would do something like
+ *
+ * char *getcwd(char * buf, size_t size)
+ * {
+ * int retval;
+ *
+ * retval = sys_getcwd(buf, size);
+ * if (retval >= 0)
+ * return buf;
+ * errno = -retval;
+ * return NULL;
+ * }
+ */
+SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size)
+{
+ int error;
+ struct path pwd, root;
+ char *page = (char *) __get_free_page(GFP_USER);
+
+ if (!page)
+ return -ENOMEM;
+
+ get_fs_root_and_pwd(current->fs, &root, &pwd);
+
+ error = -ENOENT;
+ br_read_lock(vfsmount_lock);
+ write_seqlock(&rename_lock);
+ if (!d_unlinked(pwd.dentry)) {
+ unsigned long len;
+ char *cwd = page + PAGE_SIZE;
+ int buflen = PAGE_SIZE;
+
+ prepend(&cwd, &buflen, "\0", 1);
+ error = prepend_path(&pwd, &root, &cwd, &buflen);
+ write_sequnlock(&rename_lock);
+ br_read_unlock(vfsmount_lock);
+
+ if (error < 0)
+ goto out;
+
+ /* Unreachable from current root */
+ if (error > 0) {
+ error = prepend_unreachable(&cwd, &buflen);
+ if (error)
+ goto out;
+ }
+
+ error = -ERANGE;
+ len = PAGE_SIZE + page - cwd;
+ if (len <= size) {
+ error = len;
+ if (copy_to_user(buf, cwd, len))
+ error = -EFAULT;
+ }
+ } else {
+ write_sequnlock(&rename_lock);
+ br_read_unlock(vfsmount_lock);
+ }
+
+out:
+ path_put(&pwd);
+ path_put(&root);
+ free_page((unsigned long) page);
+ return error;
+}
+
+/*
+ * Test whether new_dentry is a subdirectory of old_dentry.
+ *
+ * Trivially implemented using the dcache structure
+ */
+
+/**
+ * is_subdir - is new dentry a subdirectory of old_dentry
+ * @new_dentry: new dentry
+ * @old_dentry: old dentry
+ *
+ * Returns 1 if new_dentry is a subdirectory of the parent (at any depth).
+ * Returns 0 otherwise.
+ * Caller must ensure that "new_dentry" is pinned before calling is_subdir()
+ */
+
+int is_subdir(struct dentry *new_dentry, struct dentry *old_dentry)
+{
+ int result;
+ unsigned seq;
+
+ if (new_dentry == old_dentry)
+ return 1;
+
+ do {
+ /* for restarting inner loop in case of seq retry */
+ seq = read_seqbegin(&rename_lock);
+ /*
+ * Need rcu_readlock to protect against the d_parent trashing
+ * due to d_move
+ */
+ rcu_read_lock();
+ if (d_ancestor(old_dentry, new_dentry))
+ result = 1;
+ else
+ result = 0;
+ rcu_read_unlock();
+ } while (read_seqretry(&rename_lock, seq));
+
+ return result;
+}
+
+void d_genocide(struct dentry *root)
+{
+ struct dentry *this_parent;
+ struct list_head *next;
+ unsigned seq;
+ int locked = 0;
+
+ seq = read_seqbegin(&rename_lock);
+again:
+ this_parent = root;
+ spin_lock(&this_parent->d_lock);
+repeat:
+ next = this_parent->d_subdirs.next;
+resume:
+ while (next != &this_parent->d_subdirs) {
+ struct list_head *tmp = next;
+ struct dentry *dentry = list_entry(tmp, struct dentry, d_child);
+ next = tmp->next;
+
+ spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
+ if (d_unhashed(dentry) || !dentry->d_inode) {
+ spin_unlock(&dentry->d_lock);
+ continue;
+ }
+ if (!list_empty(&dentry->d_subdirs)) {
+ spin_unlock(&this_parent->d_lock);
+ spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_);
+ this_parent = dentry;
+ spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
+ goto repeat;
+ }
+ if (!(dentry->d_flags & DCACHE_GENOCIDE)) {
+ dentry->d_flags |= DCACHE_GENOCIDE;
+ dentry->d_count--;
+ }
+ spin_unlock(&dentry->d_lock);
+ }
+ rcu_read_lock();
+ascend:
+ if (this_parent != root) {
+ struct dentry *child = this_parent;
+ if (!(this_parent->d_flags & DCACHE_GENOCIDE)) {
+ this_parent->d_flags |= DCACHE_GENOCIDE;
+ this_parent->d_count--;
+ }
+ this_parent = child->d_parent;
+
+ spin_unlock(&child->d_lock);
+ spin_lock(&this_parent->d_lock);
+
+ /* might go back up the wrong parent if we have had a rename */
+ if (!locked && read_seqretry(&rename_lock, seq))
+ goto rename_retry;
+ next = child->d_child.next;
+ while (unlikely(child->d_flags & DCACHE_DENTRY_KILLED)) {
+ if (next == &this_parent->d_subdirs)
+ goto ascend;
+ child = list_entry(next, struct dentry, d_child);
+ next = next->next;
+ }
+ rcu_read_unlock();
+ goto resume;
+ }
+ if (!locked && read_seqretry(&rename_lock, seq))
+ goto rename_retry;
+ spin_unlock(&this_parent->d_lock);
+ rcu_read_unlock();
+ if (locked)
+ write_sequnlock(&rename_lock);
+ return;
+
+rename_retry:
+ spin_unlock(&this_parent->d_lock);
+ rcu_read_unlock();
+ if (locked)
+ goto again;
+ locked = 1;
+ write_seqlock(&rename_lock);
+ goto again;
+}
+
+/**
+ * find_inode_number - check for dentry with name
+ * @dir: directory to check
+ * @name: Name to find.
+ *
+ * Check whether a dentry already exists for the given name,
+ * and return the inode number if it has an inode. Otherwise
+ * 0 is returned.
+ *
+ * This routine is used to post-process directory listings for
+ * filesystems using synthetic inode numbers, and is necessary
+ * to keep getcwd() working.
+ */
+
+ino_t find_inode_number(struct dentry *dir, struct qstr *name)
+{
+ struct dentry * dentry;
+ ino_t ino = 0;
+
+ dentry = d_hash_and_lookup(dir, name);
+ if (dentry) {
+ if (dentry->d_inode)
+ ino = dentry->d_inode->i_ino;
+ dput(dentry);
+ }
+ return ino;
+}
+EXPORT_SYMBOL(find_inode_number);
+
+static __initdata unsigned long dhash_entries;
+static int __init set_dhash_entries(char *str)
+{
+ if (!str)
+ return 0;
+ dhash_entries = simple_strtoul(str, &str, 0);
+ return 1;
+}
+__setup("dhash_entries=", set_dhash_entries);
+
+static void __init dcache_init_early(void)
+{
+ unsigned int loop;
+
+ /* If hashes are distributed across NUMA nodes, defer
+ * hash allocation until vmalloc space is available.
+ */
+ if (hashdist)
+ return;
+
+ dentry_hashtable =
+ alloc_large_system_hash("Dentry cache",
+ sizeof(struct hlist_bl_head),
+ dhash_entries,
+ 13,
+ HASH_EARLY,
+ &d_hash_shift,
+ &d_hash_mask,
+ 0);
+
+ for (loop = 0; loop < (1U << d_hash_shift); loop++)
+ INIT_HLIST_BL_HEAD(dentry_hashtable + loop);
+}
+
+static void __init dcache_init(void)
+{
+ unsigned int loop;
+
+ /*
+ * A constructor could be added for stable state like the lists,
+ * but it is probably not worth it because of the cache nature
+ * of the dcache.
+ */
+ dentry_cache = KMEM_CACHE(dentry,
+ SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_MEM_SPREAD);
+
+ /* Hash may have been set up in dcache_init_early */
+ if (!hashdist)
+ return;
+
+ dentry_hashtable =
+ alloc_large_system_hash("Dentry cache",
+ sizeof(struct hlist_bl_head),
+ dhash_entries,
+ 13,
+ 0,
+ &d_hash_shift,
+ &d_hash_mask,
+ 0);
+
+ for (loop = 0; loop < (1U << d_hash_shift); loop++)
+ INIT_HLIST_BL_HEAD(dentry_hashtable + loop);
+}
+
+/* SLAB cache for __getname() consumers */
+struct kmem_cache *names_cachep __read_mostly;
+EXPORT_SYMBOL(names_cachep);
+
+EXPORT_SYMBOL(d_genocide);
+
+void __init vfs_caches_init_early(void)
+{
+ dcache_init_early();
+ inode_init_early();
+}
+
+void __init vfs_caches_init(unsigned long mempages)
+{
+ unsigned long reserve;
+
+ /* Base hash sizes on available memory, with a reserve equal to
+ 150% of current kernel size */
+
+ reserve = min((mempages - nr_free_pages()) * 3/2, mempages - 1);
+ mempages -= reserve;
+
+ names_cachep = kmem_cache_create("names_cache", PATH_MAX, 0,
+ SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
+
+ dcache_init();
+ inode_init();
+ files_init(mempages);
+ mnt_init();
+ bdev_cache_init();
+ chrdev_init();
+}