root/mm/msync.c

DEFINITIONS

1. sys_msync

/*
 *      linux/mm/msync.c
 *
 * Copyright (C) 1994-1999  Linus Torvalds
 */

/*
 * The msync() system call.
 */
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/mman.h>
#include <linux/file.h>
#include <linux/syscalls.h>
#include <linux/sched.h>

/*
 * MS_SYNC syncs the entire file - including mappings.
 *
 * MS_ASYNC does not start I/O (it used to, up to 2.5.67).
 * Nor does it marks the relevant pages dirty (it used to up to 2.6.17).
 * Now it doesn't do anything, since dirty pages are properly tracked.
 *
 * The application may now run fsync() to
 * write out the dirty pages and wait on the writeout and check the result.
 * Or the application may run fadvise(FADV_DONTNEED) against the fd to start
 * async writeout immediately.
 * So by _not_ starting I/O in MS_ASYNC we provide complete flexibility to
 * applications.
 */
asmlinkage long sys_msync(unsigned long start, size_t len, int flags)
{
        unsigned long end;
        struct mm_struct *mm = current->mm;
        struct vm_area_struct *vma;
        int unmapped_error = 0;
        int error = -EINVAL;

        if (flags & ~(MS_ASYNC | MS_INVALIDATE | MS_SYNC))
                goto out;
        if (start & ~PAGE_MASK)
                goto out;
        if ((flags & MS_ASYNC) && (flags & MS_SYNC))
                goto out;
        error = -ENOMEM;
        len = (len + ~PAGE_MASK) & PAGE_MASK;
        end = start + len;
        if (end < start)
                goto out;
        error = 0;
        if (end == start)
                goto out;
        /*
         * If the interval [start,end) covers some unmapped address ranges,
         * just ignore them, but return -ENOMEM at the end.
         */
        down_read(&mm->mmap_sem);
        vma = find_vma(mm, start);
        for (;;) {
                struct file *file;

                /* Still start < end. */
                error = -ENOMEM;
                if (!vma)
                        goto out_unlock;
                /* Here start < vma->vm_end. */
                if (start < vma->vm_start) {
                        start = vma->vm_start;
                        if (start >= end)
                                goto out_unlock;
                        unmapped_error = -ENOMEM;
                }
                /* Here vma->vm_start <= start < vma->vm_end. */
                if ((flags & MS_INVALIDATE) &&
                                (vma->vm_flags & VM_LOCKED)) {
                        error = -EBUSY;
                        goto out_unlock;
                }
                file = vma->vm_file;
                start = vma->vm_end;
                if ((flags & MS_SYNC) && file &&
                                (vma->vm_flags & VM_SHARED)) {
                        get_file(file);
                        up_read(&mm->mmap_sem);
                        error = do_fsync(file, 0);
                        fput(file);
                        if (error || start >= end)
                                goto out;
                        down_read(&mm->mmap_sem);
                        vma = find_vma(mm, start);
                } else {
                        if (start >= end) {
                                error = 0;
                                goto out_unlock;
                        }
                        vma = vma->vm_next;
                }
        }
out_unlock:
        up_read(&mm->mmap_sem);
out:
        return error ? : unmapped_error;
}