[ 77/95] fs/buffer.c: remove BUG() in possible but rare condition

From: Ben Hutchings
Date: Sun Sep 09 2012 - 19:32:40 EST

3.2-stable review patch. If anyone has any objections, please let me know.


From: Glauber Costa <glommer@xxxxxxxxxxxxx>

commit 61065a30af8df4b8989c2ac7a1f4b4034e4df2d5 upstream.

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


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

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@xxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
fs/buffer.c | 1 -
1 file changed, 1 deletion(-)

diff --git a/fs/buffer.c b/fs/buffer.c
index 36d6665..351e18e 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -985,7 +985,6 @@ grow_dev_page(struct block_device *bdev, sector_t block,
return page;

- BUG();
return NULL;

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