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

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>

diff --git a/fs/buffer.c b/fs/buffer.c
index 36d66653b93191c9c13c21e74dea6f511a6ac9ab..351e18ea2e53a911abcab29f57325a4f31ded786 100644 (file)
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -985,7 +985,6 @@ grow_dev_page(struct block_device *bdev, sector_t block,
        return page;
 
 failed:
-       BUG();
        unlock_page(page);
        page_cache_release(page);
        return NULL;