From: Nikolay Borisov <nborisov@suse.com>
Date: Tue, 7 May 2019 10:19:24 +0300
Git-commit: bd80d94efb83acd67d48f9f3f07483c8306085aa
Patch-mainline: 5.3
References: bsc#1174438
Subject: [PATCH] btrfs: Always use a cached extent_state in
 btrfs_lock_and_flush_ordered_range

In case no cached_state argument is passed to
btrfs_lock_and_flush_ordered_range use one locally in the function. This
optimises the case when an ordered extent is found since the unlock
function will be able to unlock that state directly without searching
for it again.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
---
 fs/btrfs/ordered-data.c | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/fs/btrfs/ordered-data.c b/fs/btrfs/ordered-data.c
index f8324f63571d..1b50811b37d0 100644
--- a/fs/btrfs/ordered-data.c
+++ b/fs/btrfs/ordered-data.c
@@ -1166,14 +1166,26 @@ void btrfs_lock_and_flush_ordered_range(struct extent_io_tree *tree,
 					struct extent_state **cached_state)
 {
 	struct btrfs_ordered_extent *ordered;
+	struct extent_state *cachedp = NULL;
+
+	if (cached_state)
+		cachedp = *cached_state;
 
 	while (1) {
-		lock_extent_bits(tree, start, end, cached_state);
+		lock_extent_bits(tree, start, end, &cachedp);
 		ordered = btrfs_lookup_ordered_range(inode, start,
 						     end - start + 1);
-		if (!ordered)
+		if (!ordered) {
+			/*
+			 * If no external cached_state has been passed then
+			 * decrement the extra ref taken for cachedp since we
+			 * aren't exposing it outside of this function
+			 */
+			if (!cached_state)
+				refcount_dec(&cachedp->refs);
 			break;
-		unlock_extent_cached(tree, start, end, cached_state, GFP_NOFS);
+		}
+		unlock_extent_cached(tree, start, end, &cachedp, GFP_NOFS);
 		btrfs_start_ordered_extent(&inode->vfs_inode, ordered, 1);
 		btrfs_put_ordered_extent(ordered);
 	}
-- 
2.26.2