From: Filipe Manana <fdmanana@gmail.com>
Date: Mon, 31 Mar 2014 13:53:25 +0000 (+0100)
Subject: Btrfs: more efficient io tree navigation on wait_extent_bit
X-Git-Tag: firefly_0821_release~176^2~3883^2~21
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=c50d3e71c3d0378bcc9e116f48dab4148854a7bb;p=firefly-linux-kernel-4.4.55.git

Btrfs: more efficient io tree navigation on wait_extent_bit

If we don't reschedule use rb_next to find the next extent state
instead of a full tree search, which is more efficient and safe
since we didn't release the io tree's lock.

Signed-off-by: Filipe David Borba Manana <fdmanana@gmail.com>
Signed-off-by: Chris Mason <clm@fb.com>
---

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index d35a3ca15fb5..0c4389634985 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -749,6 +749,7 @@ again:
 		 * our range starts
 		 */
 		node = tree_search(tree, start);
+process_node:
 		if (!node)
 			break;
 
@@ -769,7 +770,10 @@ again:
 		if (start > end)
 			break;
 
-		cond_resched_lock(&tree->lock);
+		if (!cond_resched_lock(&tree->lock)) {
+			node = rb_next(node);
+			goto process_node;
+		}
 	}
 out:
 	spin_unlock(&tree->lock);