[v2 PATCH 1/1] fs/mpage.c: forgotten WRITE_SYNC in case of WB_SYNC_ALL

[v2 PATCH 1/1] fs/mpage.c: forgotten WRITE_SYNC in case of WB_SYNC_ALL

[Roman Pen]

When data integrity operation happens (sync, fsync, fdatasync calls)
writeback control is set to WB_SYNC_ALL. In that case all write
requests are marked with WRITE_SYNC (WRITE | REQ_SYNC | REQ_NOIDLE)
indicating that caller is waiting for completion and block layer or
block device should prioritize the IO avoiding any possible delays.

But mpage writeback path ignores marking requests as WRITE_SYNC.

This patch fixes this.

Signed-off-by: Roman Pen <r.peniaev@gmail.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Tejun Heo <tj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-fsdevel@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
---
 fs/mpage.c | 23 +++++++++++++++--------
 1 file changed, 15 insertions(+), 8 deletions(-)

diff --git a/fs/mpage.c b/fs/mpage.c
index 4979ffa..4e0af5a 100644
--- a/fs/mpage.c
+++ b/fs/mpage.c
@@ -462,6 +462,7 @@ static int __mpage_writepage(struct page *page, struct writeback_control *wbc,
 	struct buffer_head map_bh;
 	loff_t i_size = i_size_read(inode);
 	int ret = 0;
+	int wr = (wbc->sync_mode == WB_SYNC_ALL ?  WRITE_SYNC : WRITE);
 
 	if (page_has_buffers(page)) {
 		struct buffer_head *head = page_buffers(page);
@@ -570,7 +571,7 @@ page_is_mapped:
 	 * This page will go to BIO.  Do we need to send this BIO off first?
 	 */
 	if (bio && mpd->last_block_in_bio != blocks[0] - 1)
-		bio = mpage_bio_submit(WRITE, bio);
+		bio = mpage_bio_submit(wr, bio);
 
 alloc_new:
 	if (bio == NULL) {
@@ -587,7 +588,7 @@ alloc_new:
 	 */
 	length = first_unmapped << blkbits;
 	if (bio_add_page(bio, page, length, 0) < length) {
-		bio = mpage_bio_submit(WRITE, bio);
+		bio = mpage_bio_submit(wr, bio);
 		goto alloc_new;
 	}
 
@@ -620,7 +621,7 @@ alloc_new:
 	set_page_writeback(page);
 	unlock_page(page);
 	if (boundary || (first_unmapped != blocks_per_page)) {
-		bio = mpage_bio_submit(WRITE, bio);
+		bio = mpage_bio_submit(wr, bio);
 		if (boundary_block) {
 			write_boundary_block(boundary_bdev,
 					boundary_block, 1 << blkbits);
@@ -632,7 +633,7 @@ alloc_new:
 
 confused:
 	if (bio)
-		bio = mpage_bio_submit(WRITE, bio);
+		bio = mpage_bio_submit(wr, bio);
 
 	if (mpd->use_writepage) {
 		ret = mapping->a_ops->writepage(page, wbc);
@@ -688,8 +689,11 @@ mpage_writepages(struct address_space *mapping,
 		};
 
 		ret = write_cache_pages(mapping, wbc, __mpage_writepage, &mpd);
-		if (mpd.bio)
-			mpage_bio_submit(WRITE, mpd.bio);
+		if (mpd.bio) {
+			int wr = (wbc->sync_mode == WB_SYNC_ALL ?
+				  WRITE_SYNC : WRITE);
+			mpage_bio_submit(wr, mpd.bio);
+		}
 	}
 	blk_finish_plug(&plug);
 	return ret;
@@ -706,8 +710,11 @@ int mpage_writepage(struct page *page, get_block_t get_block,
 		.use_writepage = 0,
 	};
 	int ret = __mpage_writepage(page, wbc, &mpd);
-	if (mpd.bio)
-		mpage_bio_submit(WRITE, mpd.bio);
+	if (mpd.bio) {
+		int wr = (wbc->sync_mode == WB_SYNC_ALL ?
+			  WRITE_SYNC : WRITE);
+		mpage_bio_submit(wr, mpd.bio);
+	}
 	return ret;
 }
 EXPORT_SYMBOL(mpage_writepage);
-- 
1.9.0

Re: [v2 PATCH 1/1] fs/mpage.c: forgotten WRITE_SYNC in case of WB_SYNC_ALL

[Andrew Morton]

On Sat, 15 Mar 2014 00:34:28 +0900 Roman Pen <r.peniaev@gmail.com> wrote:

> When data integrity operation happens (sync, fsync, fdatasync calls)
> writeback control is set to WB_SYNC_ALL. In that case all write
> requests are marked with WRITE_SYNC (WRITE | REQ_SYNC | REQ_NOIDLE)
> indicating that caller is waiting for completion and block layer or
> block device should prioritize the IO avoiding any possible delays.
> 
> But mpage writeback path ignores marking requests as WRITE_SYNC.
> 
> This patch fixes this.

Sorry, but it would be unwise to merge this without a good
understanding of its runtime effects.