path: root/mm/filemap.c
diff options
authorDarrick J. Wong <>2013-02-21 16:42:51 -0800
committerLinus Torvalds <>2013-02-21 17:22:19 -0800
commit1d1d1a767206fbe5d4c69493b7e6d2a8d08cc0a0 (patch)
tree6550294916016eac01deb596331aab1770223eab /mm/filemap.c
parent7d311cdab663f4f7ab3a4c0d5d484234406f8268 (diff)
mm: only enforce stable page writes if the backing device requires it
Create a helper function to check if a backing device requires stable page writes and, if so, performs the necessary wait. Then, make it so that all points in the memory manager that handle making pages writable use the helper function. This should provide stable page write support to most filesystems, while eliminating unnecessary waiting for devices that don't require the feature. Before this patchset, all filesystems would block, regardless of whether or not it was necessary. ext3 would wait, but still generate occasional checksum errors. The network filesystems were left to do their own thing, so they'd wait too. After this patchset, all the disk filesystems except ext3 and btrfs will wait only if the hardware requires it. ext3 (if necessary) snapshots pages instead of blocking, and btrfs provides its own bdi so the mm will never wait. Network filesystems haven't been touched, so either they provide their own stable page guarantees or they don't block at all. The blocking behavior is back to what it was before 3.0 if you don't have a disk requiring stable page writes. Here's the result of using dbench to test latency on ext2: 3.8.0-rc3: Operation Count AvgLat MaxLat ---------------------------------------- WriteX 109347 0.028 59.817 ReadX 347180 0.004 3.391 Flush 15514 29.828 287.283 Throughput 57.429 MB/sec 4 clients 4 procs max_latency=287.290 ms 3.8.0-rc3 + patches: WriteX 105556 0.029 4.273 ReadX 335004 0.005 4.112 Flush 14982 30.540 298.634 Throughput 55.4496 MB/sec 4 clients 4 procs max_latency=298.650 ms As you can see, the maximum write latency drops considerably with this patch enabled. The other filesystems (ext3/ext4/xfs/btrfs) behave similarly, but see the cover letter for those results. Signed-off-by: Darrick J. Wong <> Acked-by: Steven Whitehouse <> Reviewed-by: Jan Kara <> Cc: Adrian Hunter <> Cc: Andy Lutomirski <> Cc: Artem Bityutskiy <> Cc: Joel Becker <> Cc: Mark Fasheh <> Cc: Jens Axboe <> Cc: Eric Van Hensbergen <> Cc: Ron Minnich <> Cc: Latchesar Ionkov <> Signed-off-by: Andrew Morton <> Signed-off-by: Linus Torvalds <>
Diffstat (limited to 'mm/filemap.c')
1 files changed, 2 insertions, 1 deletions
diff --git a/mm/filemap.c b/mm/filemap.c
index 24a7ea583f0c..c610076c30e1 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1728,6 +1728,7 @@ int filemap_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
* see the dirty page and writeprotect it again.
+ wait_for_stable_page(page);
return ret;
@@ -2274,7 +2275,7 @@ repeat:
return NULL;
- wait_on_page_writeback(page);
+ wait_for_stable_page(page);
return page;