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[3/4] btrfs: remove extra barrier before waitqueue_active

Message ID 72ec4dccea7db12b160220d1adbb08e3b7ce1fa3.1424795734.git.dsterba@suse.cz (mailing list archive)
State Superseded
Headers show

Commit Message

David Sterba Feb. 24, 2015, 4:51 p.m. UTC 
Removing barriers is scary, but a call to atomic_dec_and_test implies
a barrier, so we don't need to issue another one.

Signed-off-by: David Sterba <dsterba@suse.cz>
---
 fs/btrfs/tree-log.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)
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Patch

diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
index 121df0fe5128..07ed248ef0e7 100644
--- a/fs/btrfs/tree-log.c
+++ b/fs/btrfs/tree-log.c
@@ -238,7 +238,9 @@  int btrfs_pin_log_trans(struct btrfs_root *root)
 void btrfs_end_log_trans(struct btrfs_root *root)
 {
 	if (atomic_dec_and_test(&root->log_writers)) {
-		smp_mb();
+		/*
+		 * Implicit memory barrier after atomic_dec_and_test
+		 */
 		if (waitqueue_active(&root->log_writer_wait))
 			wake_up(&root->log_writer_wait);
 	}
@@ -2610,7 +2612,9 @@  int btrfs_sync_log(struct btrfs_trans_handle *trans,
 
 	mutex_lock(&log_root_tree->log_mutex);
 	if (atomic_dec_and_test(&log_root_tree->log_writers)) {
-		smp_mb();
+		/*
+		 * Implicit memory barrier after atomic_dec_and_test
+		 */
 		if (waitqueue_active(&log_root_tree->log_writer_wait))
 			wake_up(&log_root_tree->log_writer_wait);
 	}