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>

1 files changed, 16 insertions, 4 deletions

diff --git a/fs/buffer.c b/fs/buffer.c
index 5d55a896ff78..43afaa5d6901 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -737,7 +737,7 @@ static int fsync_buffers_list(spinlock_t *lock, struct list_head *list)
 {
         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 @@ static int fsync_buffers_list(spinlock_t *lock, struct list_head *list)
                                  * 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 @@ void ll_rw_block(int rw, int nr, struct buffer_head *bhs[])
         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);