• Peter Zijlstra's avatar
    [PATCH] mm: msync() cleanup · 204ec841
    Peter Zijlstra authored
    
    With the tracking of dirty pages properly done now, msync doesn't need to scan
    the PTEs anymore to determine the dirty status.
    
    From: Hugh Dickins <hugh@veritas.com>
    
    In looking to do that, I made some other tidyups: can remove several
    #includes, and sys_msync loop termination not quite right.
    
    Most of those points are criticisms of the existing sys_msync, not of your
    patch.  In particular, the loop termination errors were introduced in 2.6.17:
    I did notice this shortly before it came out, but decided I was more likely to
    get it wrong myself, and make matters worse if I tried to rush a last-minute
    fix in.  And it's not terribly likely to go wrong, nor disastrous if it does
    go wrong (may miss reporting an unmapped area; may also fsync file of a
    following vma).
    Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
    Signed-off-by: default avatarHugh Dickins <hugh@veritas.com>
    Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
    204ec841
msync.c 2.4 KB
/*
 *	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>

/*
 * 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;
}