From c2025f6518c071006c97379a696aa7ddc2fc7ba2 Mon Sep 17 00:00:00 2001
From: Josef Bacik <jbacik@fusionio.com>
Date: Fri, 20 Jul 2012 16:25:24 -0400
Subject: [PATCH] --- yaml --- r: 318866 b: refs/heads/master c:
 51561ffec9614618f3da362f9d1b03a95b717484 h: refs/heads/master v: v3

---
 [refs]                     | 2 +-
 trunk/fs/btrfs/extent_io.c | 9 +++++++++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/[refs] b/[refs]
index 9826faa01792..135370bf0214 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 594831c4b232b094d645503ecedec2e35dcebdf3
+refs/heads/master: 51561ffec9614618f3da362f9d1b03a95b717484
diff --git a/trunk/fs/btrfs/extent_io.c b/trunk/fs/btrfs/extent_io.c
index e1939a6c7478..97efc2f22597 100644
--- a/trunk/fs/btrfs/extent_io.c
+++ b/trunk/fs/btrfs/extent_io.c
@@ -3077,8 +3077,15 @@ static int lock_extent_buffer_for_io(struct extent_buffer *eb,
 		}
 	}
 
+	/*
+	 * We need to do this to prevent races in people who check if the eb is
+	 * under IO since we can end up having no IO bits set for a short period
+	 * of time.
+	 */
+	spin_lock(&eb->refs_lock);
 	if (test_and_clear_bit(EXTENT_BUFFER_DIRTY, &eb->bflags)) {
 		set_bit(EXTENT_BUFFER_WRITEBACK, &eb->bflags);
+		spin_unlock(&eb->refs_lock);
 		btrfs_set_header_flag(eb, BTRFS_HEADER_FLAG_WRITTEN);
 		spin_lock(&fs_info->delalloc_lock);
 		if (fs_info->dirty_metadata_bytes >= eb->len)
@@ -3087,6 +3094,8 @@ static int lock_extent_buffer_for_io(struct extent_buffer *eb,
 			WARN_ON(1);
 		spin_unlock(&fs_info->delalloc_lock);
 		ret = 1;
+	} else {
+		spin_unlock(&eb->refs_lock);
 	}
 
 	btrfs_tree_unlock(eb);