One can use btrfs-corrupt-block to hit BUG_ON() in merge_bio(),
thus this aims to stop anyone to panic the whole system by using
their btrfs.
Since the error in merge_bio can only come from __btrfs_map_block()
when chunk tree mapping has something insane and __btrfs_map_block()
has already had printed the reason, we can just return errors in
merge_bio.
Signed-off-by: Liu Bo <bo.li....@oracle.com>
---
fs/btrfs/extent_io.c | 1 -
fs/btrfs/inode.c | 8 ++++++--
2 files changed, 6 insertions(+), 3 deletions(-)
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index aa44d3e..a8661fb 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -2756,7 +2756,6 @@ static int merge_bio(int rw, struct extent_io_tree *tree,
struct page *page,
if (tree->ops && tree->ops->merge_bio_hook)
ret = tree->ops->merge_bio_hook(rw, page, offset, size, bio,
bio_flags);
- BUG_ON(ret < 0);
return ret;
}
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 8b1212e..d203c06 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -1822,6 +1822,10 @@ static void btrfs_clear_bit_hook(struct inode *inode,
/*
* extent_io.c merge_bio_hook, this must check the chunk tree to make sure
* we don't create bios that span stripes or chunks
+ *
+ * return 1 if page cannot be merged to bio
+ * return 0 if page can be merged to bio
+ * return error otherwise
*/
int btrfs_merge_bio_hook(int rw, struct page *page, unsigned long offset,
size_t size, struct bio *bio,
@@ -1840,8 +1844,8 @@ int btrfs_merge_bio_hook(int rw, struct page *page,
unsigned long offset,
map_length = length;
ret = btrfs_map_block(root->fs_info, rw, logical,
&map_length, NULL, 0);
- /* Will always return 0 with map_multi == NULL */
- BUG_ON(ret < 0);
+ if (ret < 0)
+ return ret;
if (map_length < length + size)
return 1;
return 0;
--
2.5.5
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