linux/mm/msync.c
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   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        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. Besides, if the
  59         * flag is MS_ASYNC (w/o MS_INVALIDATE) the result would be -ENOMEM
  60         * anyway and there is nothing left to do, so return immediately.
  61         */
  62        mmap_read_lock(mm);
  63        vma = find_vma(mm, start);
  64        for (;;) {
  65                struct file *file;
  66                loff_t fstart, fend;
  67
  68                /* Still start < end. */
  69                error = -ENOMEM;
  70                if (!vma)
  71                        goto out_unlock;
  72                /* Here start < vma->vm_end. */
  73                if (start < vma->vm_start) {
  74                        if (flags == MS_ASYNC)
  75                                goto out_unlock;
  76                        start = vma->vm_start;
  77                        if (start >= end)
  78                                goto out_unlock;
  79                        unmapped_error = -ENOMEM;
  80                }
  81                /* Here vma->vm_start <= start < vma->vm_end. */
  82                if ((flags & MS_INVALIDATE) &&
  83                                (vma->vm_flags & VM_LOCKED)) {
  84                        error = -EBUSY;
  85                        goto out_unlock;
  86                }
  87                file = vma->vm_file;
  88                fstart = (start - vma->vm_start) +
  89                         ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
  90                fend = fstart + (min(end, vma->vm_end) - start) - 1;
  91                start = vma->vm_end;
  92                if ((flags & MS_SYNC) && file &&
  93                                (vma->vm_flags & VM_SHARED)) {
  94                        get_file(file);
  95                        mmap_read_unlock(mm);
  96                        error = vfs_fsync_range(file, fstart, fend, 1);
  97                        fput(file);
  98                        if (error || start >= end)
  99                                goto out;
 100                        mmap_read_lock(mm);
 101                        vma = find_vma(mm, start);
 102                } else {
 103                        if (start >= end) {
 104                                error = 0;
 105                                goto out_unlock;
 106                        }
 107                        vma = vma->vm_next;
 108                }
 109        }
 110out_unlock:
 111        mmap_read_unlock(mm);
 112out:
 113        return error ? : unmapped_error;
 114}
 115
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