From 59819293977d4265a206bf6fd3b05ef2f34f56f7 Mon Sep 17 00:00:00 2001
From: Josef Bacik <josef@redhat.com>
Date: Fri, 9 Mar 2012 09:51:43 -0500
Subject: [PATCH] --- yaml --- r: 297845 b: refs/heads/master c:
 115391d2315239164e400a8259b26392afccf3bd h: refs/heads/master i:   297843:
 d693a443a461cf759e98deb94019e37f3d9a755c v: v3

---
 [refs]                     |  2 +-
 trunk/fs/btrfs/extent_io.c | 10 ++++++++--
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/[refs] b/[refs]
index 8ee2818586b4..09cbb99b59de 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 4f2de97acee6532b36dd6e995b858343771ad126
+refs/heads/master: 115391d2315239164e400a8259b26392afccf3bd
diff --git a/trunk/fs/btrfs/extent_io.c b/trunk/fs/btrfs/extent_io.c
index 0381b6007ae4..0f74262911be 100644
--- a/trunk/fs/btrfs/extent_io.c
+++ b/trunk/fs/btrfs/extent_io.c
@@ -3750,7 +3750,7 @@ struct extent_buffer *alloc_extent_buffer(struct extent_io_tree *tree,
 	}
 	if (uptodate)
 		set_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags);
-
+again:
 	ret = radix_tree_preload(GFP_NOFS & ~__GFP_HIGHMEM);
 	if (ret)
 		goto free_eb;
@@ -3760,7 +3760,13 @@ struct extent_buffer *alloc_extent_buffer(struct extent_io_tree *tree,
 	if (ret == -EEXIST) {
 		exists = radix_tree_lookup(&tree->buffer,
 						start >> PAGE_CACHE_SHIFT);
-		atomic_inc(&exists->refs);
+		if (!atomic_inc_not_zero(&exists->refs)) {
+			spin_unlock(&tree->buffer_lock);
+			radix_tree_preload_end();
+			synchronize_rcu();
+			exists = NULL;
+			goto again;
+		}
 		spin_unlock(&tree->buffer_lock);
 		radix_tree_preload_end();
 		goto free_eb;