commit 9cf6b720f84d6999ff9a514d0a939dd183846aaf
author Jens Axboe <jens.axboe@oracle.com> Mon Apr 06 14:48:03 2009 +0200
committer Linus Torvalds <torvalds@linux-foundation.org> Mon Apr 06 08:04:53 2009 -0700
tree 13f58881927769c792b8b1f685282aa67264b9ed
parent a1f242524c3c1f5d40f1c9c343427e34d1aadd6e

block: fsync_buffers_list() should use SWRITE_SYNC_PLUG

Then it can submit all the buffers without unplugging for each one.
We will kick off the pending IO if we come across a new address space.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/buffer.c

diff --git a/fs/buffer.c b/fs/buffer.c
index 5d55a89..43afaa5 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -737,7 +737,7 @@
 {
 	struct buffer_head *bh;
 	struct list_head tmp;
-	struct address_space *mapping;
+	struct address_space *mapping, *prev_mapping = NULL;
 	int err = 0, err2;
 
 	INIT_LIST_HEAD(&tmp);
@@ -762,7 +762,18 @@
 				 * contents - it is a noop if I/O is still in
 				 * flight on potentially older contents.
 				 */
-				ll_rw_block(SWRITE_SYNC, 1, &bh);
+				ll_rw_block(SWRITE_SYNC_PLUG, 1, &bh);
+
+				/*
+				 * Kick off IO for the previous mapping. Note
+				 * that we will not run the very last mapping,
+				 * wait_on_buffer() will do that for us
+				 * through sync_buffer().
+				 */
+				if (prev_mapping && prev_mapping != mapping)
+					blk_run_address_space(prev_mapping);
+				prev_mapping = mapping;
+
 				brelse(bh);
 				spin_lock(lock);
 			}
@@ -2957,12 +2968,13 @@
 	for (i = 0; i < nr; i++) {
 		struct buffer_head *bh = bhs[i];
 
-		if (rw == SWRITE || rw == SWRITE_SYNC)
+		if (rw == SWRITE || rw == SWRITE_SYNC || rw == SWRITE_SYNC_PLUG)
 			lock_buffer(bh);
 		else if (!trylock_buffer(bh))
 			continue;
 
-		if (rw == WRITE || rw == SWRITE || rw == SWRITE_SYNC) {
+		if (rw == WRITE || rw == SWRITE || rw == SWRITE_SYNC ||
+		    rw == SWRITE_SYNC_PLUG) {
 			if (test_clear_buffer_dirty(bh)) {
 				bh->b_end_io = end_buffer_write_sync;
 				get_bh(bh);