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>

3 files changed, 4 insertions, 2 deletions

diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index 14f1c5a0b2d2..d02c27cd14c7 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);
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index b05d35a7c0f1..8d6f55fbd28e 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -3308,7 +3308,7 @@ int try_release_extent_mapping(struct extent_map_tree *map,
                         len = end - start + 1;
                         write_lock(&map->lock);
                         em = lookup_extent_mapping(map, start, len);
-                        if (IS_ERR_OR_NULL(em)) {
+                        if (!em) {
                                 write_unlock(&map->lock);
                                 break;
                         }
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index d8f282b5baa9..cd040bf3fd87 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1954,7 +1954,7 @@ static int btrfs_relocate_chunk(struct btrfs_root *root,
         em = lookup_extent_mapping(em_tree, chunk_offset, 1);
         read_unlock(&em_tree->lock);
 
-        BUG_ON(em->start > chunk_offset ||
+        BUG_ON(!em || em->start > chunk_offset ||
                em->start + em->len < chunk_offset);
         map = (struct map_lookup *)em->bdev;