LXR linux/mm/msync.c

   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 */
  32SYSCALL_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        if (flags & ~(MS_ASYNC | MS_INVALIDATE | MS_SYNC))
  41                goto out;
  42        if (offset_in_page(start))
  43                goto out;
  44        if ((flags & MS_ASYNC) && (flags & MS_SYNC))
  45                goto out;
  46        error = -ENOMEM;
  47        len = (len + ~PAGE_MASK) & PAGE_MASK;
  48        end = start + len;
  49        if (end < start)
  50                goto out;
  51        error = 0;
  52        if (end == start)
  53                goto out;
  54        /*
  55         * If the interval [start,end) covers some unmapped address ranges,
  56         * just ignore them, but return -ENOMEM at the end.
  57         */
  58        down_read(&mm->mmap_sem);
  59        vma = find_vma(mm, start);
  60        for (;;) {
  61                struct file *file;
  62                loff_t fstart, fend;
  63
  64                /* Still start < end. */
  65                error = -ENOMEM;
  66                if (!vma)
  67                        goto out_unlock;
  68                /* Here start < vma->vm_end. */
  69                if (start < vma->vm_start) {
  70                        start = vma->vm_start;
  71                        if (start >= end)
  72                                goto out_unlock;
  73                        unmapped_error = -ENOMEM;
  74                }
  75                /* Here vma->vm_start <= start < vma->vm_end. */
  76                if ((flags & MS_INVALIDATE) &&
  77                                (vma->vm_flags & VM_LOCKED)) {
  78                        error = -EBUSY;
  79                        goto out_unlock;
  80                }
  81                file = vma->vm_file;
  82                fstart = (start - vma->vm_start) +
  83                         ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
  84                fend = fstart + (min(end, vma->vm_end) - start) - 1;
  85                start = vma->vm_end;
  86                if ((flags & MS_SYNC) && file &&
  87                                (vma->vm_flags & VM_SHARED)) {
  88                        get_file(file);
  89                        up_read(&mm->mmap_sem);
  90                        error = vfs_fsync_range(file, fstart, fend, 1);
  91                        fput(file);
  92                        if (error || start >= end)
  93                                goto out;
  94                        down_read(&mm->mmap_sem);
  95                        vma = find_vma(mm, start);
  96                } else {
  97                        if (start >= end) {
  98                                error = 0;
  99                                goto out_unlock;
 100                        }
 101                        vma = vma->vm_next;
 102                }
 103        }
 104out_unlock:
 105        up_read(&mm->mmap_sem);
 106out:
 107        return error ? : unmapped_error;
 108}
 109