Merge branch 'for-linus-4.1' of git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs

Pull btrfs fixes from Chris Mason:
 "The first commit is a fix from Filipe for a very old extent buffer
  reuse race that triggered a BUG_ON.  It hasn't come up often, I looked
  through old logs at FB and we hit it a handful of times over the last
  year.

  The rest are other corners he hit during testing"

* 'for-linus-4.1' of git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs:
  Btrfs: fix race when reusing stale extent buffers that leads to BUG_ON
  Btrfs: fix race between block group creation and their cache writeout
  Btrfs: fix panic when starting bg cache writeout after IO error
  Btrfs: fix crash after inode cache writeback failure

1 files changed, 10 insertions, 4 deletions

diff --git a/fs/btrfs/ordered-data.c b/fs/btrfs/ordered-data.c
index 157cc54fc634..760c4a5e096b 100644
--- a/fs/btrfs/ordered-data.c
+++ b/fs/btrfs/ordered-data.c
@@ -722,6 +722,7 @@ void btrfs_start_ordered_extent(struct inode *inode,
 int btrfs_wait_ordered_range(struct inode *inode, u64 start, u64 len)
 {
 	int ret = 0;
+	int ret_wb = 0;
 	u64 end;
 	u64 orig_end;
 	struct btrfs_ordered_extent *ordered;
@@ -741,9 +742,14 @@ int btrfs_wait_ordered_range(struct inode *inode, u64 start, u64 len)
 	if (ret)
 		return ret;
 
-	ret = filemap_fdatawait_range(inode->i_mapping, start, orig_end);
-	if (ret)
-		return ret;
+	/*
+	 * If we have a writeback error don't return immediately. Wait first
+	 * for any ordered extents that haven't completed yet. This is to make
+	 * sure no one can dirty the same page ranges and call writepages()
+	 * before the ordered extents complete - to avoid failures (-EEXIST)
+	 * when adding the new ordered extents to the ordered tree.
+	 */
+	ret_wb = filemap_fdatawait_range(inode->i_mapping, start, orig_end);
 
 	end = orig_end;
 	while (1) {
@@ -767,7 +773,7 @@ int btrfs_wait_ordered_range(struct inode *inode, u64 start, u64 len)
 			break;
 		end--;
 	}
-	return ret;
+	return ret_wb ? ret_wb : ret;
 }
 
 /*