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>

1 files changed, 2 insertions, 0 deletions

diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index 14f1c5a0b2d..d02c27cd14c 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -588,6 +588,8 @@ int btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
                                    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);