btrfs: properly clear end of the unreserved range in cow_file_range

commit 12b2d64 upstream.

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 before the jump, so there might no
range be left from the newly incremented start to end.  Move the check for
'start < end' so that it is reached by also for the !extent_reserved case.

CC: stable@vger.kernel.org # 6.1+
Fixes: a315e68 ("Btrfs: fix invalid attempt to free reserved space on failure to cow range")
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Christoph Hellwig

fs/btrfs/inode.c

@@ -1429,8 +1429,6 @@ static noinline int cow_file_range(struct btrfs_inode *inode,
 					     clear_bits,
 					     page_ops);
 		start += cur_alloc_size;
-		if (start >= end)
-			return ret;
 	}
 
 	/*
@@ -1439,9 +1437,11 @@ 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;
 }