fs/buffer.c: remove BUG() in possible but rare condition

commit 61065a30af8df4b8989c2ac7a1f4b4034e4df2d5 upstream.

While stressing the kernel with with failing allocations today, I hit the
following chain of events:

alloc_page_buffers():

	bh = alloc_buffer_head(GFP_NOFS);
	if (!bh)
		goto no_grow; <= path taken

grow_dev_page():
        bh = alloc_page_buffers(page, size, 0);
        if (!bh)
                goto failed;  <= taken, consequence of the above

and then the failed path BUG()s the kernel.

The failure is inserted a litte bit artificially, but even then, I see no
reason why it should be deemed impossible in a real box.

Even though this is not a condition that we expect to see around every
time, failed allocations are expected to be handled, and BUG() sounds just
too much.  As a matter of fact, grow_dev_page() can return NULL just fine
in other circumstances, so I propose we just remove it, then.

Signed-off-by: Glauber Costa <glommer@parallels.com>
Cc: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

1 files changed, 0 insertions, 1 deletions

diff --git a/fs/buffer.c b/fs/buffer.c
index 4115eca2dc8..e0bc0215a6e 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -1037,7 +1037,6 @@ grow_dev_page(struct block_device *bdev, sector_t block,
 	return page;
 
 failed:
-	BUG();
 	unlock_page(page);
 	page_cache_release(page);
 	return NULL;