Subject: + sync-only-the-requested-range-in-msync.patch added to -mm tree
To: matthew.r.wilcox@xxxxxxxxx,clm@xxxxxx,hch@xxxxxx,jmoyer@xxxxxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Tue, 20 May 2014 16:01:24 -0700
The patch titled
Subject: mm/msync.c: sync only the requested range in msync()
has been added to the -mm tree. Its filename is
sync-only-the-requested-range-in-msync.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/sync-only-the-requested-range-in-msync.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/sync-only-the-requested-range-in-msync.patch
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From: Matthew Wilcox <matthew.r.wilcox@xxxxxxxxx>
Subject: mm/msync.c: sync only the requested range in msync()
msync() currently syncs more than POSIX requires or BSD or Solaris
implement. It is supposed to be equivalent to fdatasync(), not fsync(),
and it is only supposed to sync the portion of the file that overlaps the
range passed to msync.
If the VMA is non-linear, fall back to syncing the entire file, but we
still optimise to only fdatasync() the entire file, not the full fsync().
akpm: there are obvious concerns with bck-compatibility: is anyone relying
on the undocumented side-effect for their data integrity? And how would
they ever know if this change broke their data integrity?
We think the risk is reasonably low, and this patch brings the kernel into
line with other OS's and with what the manpage has always said...
Signed-off-by: Matthew Wilcox <matthew.r.wilcox@xxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Acked-by: Jeff Moyer <jmoyer@xxxxxxxxxx>
Cc: Chris Mason <clm@xxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/msync.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff -puN mm/msync.c~sync-only-the-requested-range-in-msync mm/msync.c
--- a/mm/msync.c~sync-only-the-requested-range-in-msync
+++ a/mm/msync.c
@@ -58,6 +58,7 @@ SYSCALL_DEFINE3(msync, unsigned long, st
vma = find_vma(mm, start);
for (;;) {
struct file *file;
+ loff_t fstart, fend;
/* Still start < end. */
error = -ENOMEM;
@@ -77,12 +78,17 @@ SYSCALL_DEFINE3(msync, unsigned long, st
goto out_unlock;
}
file = vma->vm_file;
+ fstart = start + ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
+ fend = fstart + (min(end, vma->vm_end) - start) - 1;
start = vma->vm_end;
if ((flags & MS_SYNC) && file &&
(vma->vm_flags & VM_SHARED)) {
get_file(file);
up_read(&mm->mmap_sem);
- error = vfs_fsync(file, 0);
+ if (vma->vm_flags & VM_NONLINEAR)
+ error = vfs_fsync(file, 1);
+ else
+ error = vfs_fsync_range(file, fstart, fend, 1);
fput(file);
if (error || start >= end)
goto out;
_
Patches currently in -mm which might be from matthew.r.wilcox@xxxxxxxxx are
mm-introduce-do_shared_fault-and-drop-do_fault-fix-fix.patch
fs-bufferc-remove-block_write_full_page_endio.patch
fs-mpagec-factor-clean_buffers-out-of-__mpage_writepage.patch
fs-mpagec-factor-page_endio-out-of-mpage_end_io.patch
fs-block_devc-add-bdev_read_page-and-bdev_write_page.patch
swap-use-bdev_read_page-bdev_write_page.patch
swap-use-bdev_read_page-bdev_write_page-fix.patch
brd-add-support-for-rw_page.patch
brd-return-enospc-rather-than-enomem-on-page-allocation-failure.patch
sync-only-the-requested-range-in-msync.patch
do_shared_fault-check-that-mmap_sem-is-held.patch
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