[PATCH 3/9] btrfs: fix an error handling corner case in cow_file_range

[Christoph Hellwig <hch@lst.de>]

When the call to btrfs_reloc_clone_csums in cow_file_range returns an
error, we jump to the out_unlock label with the extent_reserved variable
set to false.   The cleanup at the label will then call
extent_clear_unlock_delalloc on the range from start to end.  But we've
already added cur_alloc_size to start, so there might no range be left
from the newly increment start to end.  Move the check for start < end
so that it is reached by also for the !extent_reserved case.

Fixes: a315e68f6e8b ("Btrfs: fix invalid attempt to free reserved space on failure to cow range")
Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 fs/btrfs/inode.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index ae1bda58004b26..20bee7f8dae01c 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -1548,8 +1548,6 @@ static noinline int cow_file_range(struct btrfs_inode *inode,
 					     clear_bits,
 					     page_ops);
 		start += cur_alloc_size;
-		if (start >= end)
-			return ret;
 	}
 
 	/*
@@ -1558,9 +1556,11 @@ static noinline int cow_file_range(struct btrfs_inode *inode,
 	 * space_info's bytes_may_use counter, reserved in
 	 * btrfs_check_data_free_space().
 	 */
-	extent_clear_unlock_delalloc(inode, start, end, locked_page,
-				     clear_bits | EXTENT_CLEAR_DATA_RESV,
-				     page_ops);
+	if (start < end) {
+		clear_bits |= EXTENT_CLEAR_DATA_RESV;
+		extent_clear_unlock_delalloc(inode, start, end, locked_page,
+					     clear_bits, page_ops);
+	}
 	return ret;
 }
 
-- 
2.39.2