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[PATCH 4.9 76/78] btrfs: use correct compare function of dirty_metadata_bytes




4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ethan Lien <ethanlien@xxxxxxxxxxxx>

commit d814a49198eafa6163698bdd93961302f3a877a4 upstream.

We use customized, nodesize batch value to update dirty_metadata_bytes.
We should also use batch version of compare function or we will easily
goto fast path and get false result from percpu_counter_compare().

Fixes: e2d845211eda ("Btrfs: use percpu counter for dirty metadata count")
CC: stable@xxxxxxxxxxxxxxx # 4.4+
Signed-off-by: Ethan Lien <ethanlien@xxxxxxxxxxxx>
Reviewed-by: Nikolay Borisov <nborisov@xxxxxxxx>
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
nb: Rebased on 4.4.y ]
Signed-off-by: Nikolay Borisov <nborisov@xxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 fs/btrfs/disk-io.c |   10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1096,8 +1096,9 @@ static int btree_writepages(struct addre
 
 		fs_info = BTRFS_I(mapping->host)->root->fs_info;
 		/* this is a bit racy, but that's ok */
-		ret = percpu_counter_compare(&fs_info->dirty_metadata_bytes,
-					     BTRFS_DIRTY_METADATA_THRESH);
+		ret = __percpu_counter_compare(&fs_info->dirty_metadata_bytes,
+					     BTRFS_DIRTY_METADATA_THRESH,
+					     fs_info->dirty_metadata_batch);
 		if (ret < 0)
 			return 0;
 	}
@@ -4107,8 +4108,9 @@ static void __btrfs_btree_balance_dirty(
 	if (flush_delayed)
 		btrfs_balance_delayed_items(root);
 
-	ret = percpu_counter_compare(&root->fs_info->dirty_metadata_bytes,
-				     BTRFS_DIRTY_METADATA_THRESH);
+	ret = __percpu_counter_compare(&root->fs_info->dirty_metadata_bytes,
+				     BTRFS_DIRTY_METADATA_THRESH,
+				     root->fs_info->dirty_metadata_batch);
 	if (ret > 0) {
 		balance_dirty_pages_ratelimited(
 				   root->fs_info->btree_inode->i_mapping);