On 08/23/2016 07:49 AM, Ming Lei wrote:
After arbitrary bio size is supported, the incoming bio may
be very big. We have to split the bio into small bios so that
each holds at most BIO_MAX_PAGES bvecs for safety reason, such
as bio_clone().
This patch fixes the following kernel crash:
[ 172.660142] BUG: unable to handle kernel NULL pointer dereference at
0000000000000028
[ 172.660229] IP: [<ffffffff811e53b4>] bio_trim+0xf/0x2a
[ 172.660289] PGD 7faf3e067 PUD 7f9279067 PMD 0
[ 172.660399] Oops: 0000 [#1] SMP
[...]
[ 172.664780] Call Trace:
[ 172.664813] [<ffffffffa007f3be>] ? raid1_make_request+0x2e8/0xad7 [raid1]
[ 172.664846] [<ffffffff811f07da>] ? blk_queue_split+0x377/0x3d4
[ 172.664880] [<ffffffffa005fb5f>] ? md_make_request+0xf6/0x1e9 [md_mod]
[ 172.664912] [<ffffffff811eb860>] ? generic_make_request+0xb5/0x155
[ 172.664947] [<ffffffffa0445c89>] ? prio_io+0x85/0x95 [bcache]
[ 172.664981] [<ffffffffa0448252>] ? register_cache_set+0x355/0x8d0 [bcache]
[ 172.665016] [<ffffffffa04497d3>] ? register_bcache+0x1006/0x1174 [bcache]
The issue can be reproduced by the following steps:
- create one raid1 over two virtio-blk
- build bcache device over the above raid1 and another cache device
and bucket size is set as 2Mbytes
- set cache mode as writeback
- run random write over ext4 on the bcache device
Applied for 4.8, thanks.
--
Jens Axboe
