Btrfs: check return value of lookup_extent_mapping() correctly
This patch corrects error checking of lookup_extent_mapping().
Signed-off-by: Tsutomu Itoh <t-itoh@jp.fujitsu.com>
diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index 14f1c5a..d02c27c 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -588,6 +588,8 @@
page_offset(bio->bi_io_vec->bv_page),
PAGE_CACHE_SIZE);
read_unlock(&em_tree->lock);
+ if (!em)
+ return -EIO;
compressed_len = em->block_len;
cb = kmalloc(compressed_bio_size(root, compressed_len), GFP_NOFS);