| xj | b04a402 | 2021-11-25 15:01:52 +0800 | [diff] [blame] | 1 | // SPDX-License-Identifier: GPL-2.0 |
| 2 | /* |
| 3 | * linux/mm/msync.c |
| 4 | * |
| 5 | * Copyright (C) 1994-1999 Linus Torvalds |
| 6 | */ |
| 7 | |
| 8 | /* |
| 9 | * The msync() system call. |
| 10 | */ |
| 11 | #include <linux/fs.h> |
| 12 | #include <linux/mm.h> |
| 13 | #include <linux/mman.h> |
| 14 | #include <linux/file.h> |
| 15 | #include <linux/syscalls.h> |
| 16 | #include <linux/sched.h> |
| 17 | |
| 18 | /* |
| 19 | * MS_SYNC syncs the entire file - including mappings. |
| 20 | * |
| 21 | * MS_ASYNC does not start I/O (it used to, up to 2.5.67). |
| 22 | * Nor does it marks the relevant pages dirty (it used to up to 2.6.17). |
| 23 | * Now it doesn't do anything, since dirty pages are properly tracked. |
| 24 | * |
| 25 | * The application may now run fsync() to |
| 26 | * write out the dirty pages and wait on the writeout and check the result. |
| 27 | * Or the application may run fadvise(FADV_DONTNEED) against the fd to start |
| 28 | * async writeout immediately. |
| 29 | * So by _not_ starting I/O in MS_ASYNC we provide complete flexibility to |
| 30 | * applications. |
| 31 | */ |
| 32 | SYSCALL_DEFINE3(msync, unsigned long, start, size_t, len, int, flags) |
| 33 | { |
| 34 | unsigned long end; |
| 35 | struct mm_struct *mm = current->mm; |
| 36 | struct vm_area_struct *vma; |
| 37 | int unmapped_error = 0; |
| 38 | int error = -EINVAL; |
| 39 | |
| 40 | start = untagged_addr(start); |
| 41 | |
| 42 | if (flags & ~(MS_ASYNC | MS_INVALIDATE | MS_SYNC)) |
| 43 | goto out; |
| 44 | if (offset_in_page(start)) |
| 45 | goto out; |
| 46 | if ((flags & MS_ASYNC) && (flags & MS_SYNC)) |
| 47 | goto out; |
| 48 | error = -ENOMEM; |
| 49 | len = (len + ~PAGE_MASK) & PAGE_MASK; |
| 50 | end = start + len; |
| 51 | if (end < start) |
| 52 | goto out; |
| 53 | error = 0; |
| 54 | if (end == start) |
| 55 | goto out; |
| 56 | /* |
| 57 | * If the interval [start,end) covers some unmapped address ranges, |
| 58 | * just ignore them, but return -ENOMEM at the end. |
| 59 | */ |
| 60 | down_read(&mm->mmap_sem); |
| 61 | vma = find_vma(mm, start); |
| 62 | for (;;) { |
| 63 | struct file *file; |
| 64 | loff_t fstart, fend; |
| 65 | |
| 66 | /* Still start < end. */ |
| 67 | error = -ENOMEM; |
| 68 | if (!vma) |
| 69 | goto out_unlock; |
| 70 | /* Here start < vma->vm_end. */ |
| 71 | if (start < vma->vm_start) { |
| 72 | start = vma->vm_start; |
| 73 | if (start >= end) |
| 74 | goto out_unlock; |
| 75 | unmapped_error = -ENOMEM; |
| 76 | } |
| 77 | /* Here vma->vm_start <= start < vma->vm_end. */ |
| 78 | if ((flags & MS_INVALIDATE) && |
| 79 | (vma->vm_flags & VM_LOCKED)) { |
| 80 | error = -EBUSY; |
| 81 | goto out_unlock; |
| 82 | } |
| 83 | file = vma->vm_file; |
| 84 | fstart = (start - vma->vm_start) + |
| 85 | ((loff_t)vma->vm_pgoff << PAGE_SHIFT); |
| 86 | fend = fstart + (min(end, vma->vm_end) - start) - 1; |
| 87 | start = vma->vm_end; |
| 88 | if ((flags & MS_SYNC) && file && |
| 89 | (vma->vm_flags & VM_SHARED)) { |
| 90 | get_file(file); |
| 91 | up_read(&mm->mmap_sem); |
| 92 | error = vfs_fsync_range(file, fstart, fend, 1); |
| 93 | fput(file); |
| 94 | if (error || start >= end) |
| 95 | goto out; |
| 96 | down_read(&mm->mmap_sem); |
| 97 | vma = find_vma(mm, start); |
| 98 | } else { |
| 99 | if (start >= end) { |
| 100 | error = 0; |
| 101 | goto out_unlock; |
| 102 | } |
| 103 | vma = vma->vm_next; |
| 104 | } |
| 105 | } |
| 106 | out_unlock: |
| 107 | up_read(&mm->mmap_sem); |
| 108 | out: |
| 109 | return error ? : unmapped_error; |
| 110 | } |