On Wed, Apr 06, 2016 at 08:47:56AM +0800, Ming Lei wrote: > On Wed, Apr 6, 2016 at 2:27 AM, Shaohua Li <s...@fb.com> wrote: > > On Wed, Apr 06, 2016 at 01:44:06AM +0800, 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] > >> > >> Fixes: 54efd50(block: make generic_make_request handle arbitrarily sized > >> bios) > > > > this bug is introduced by d2be537c3ba > >> Reported-by: Sebastian Roesner <sroesner-kernel...@roesner-online.de> > >> Reported-by: Eric Wheeler <bca...@lists.ewheeler.net> > >> Cc: sta...@vger.kernel.org (4.2+) > >> Cc: Shaohua Li <s...@fb.com> > >> Signed-off-by: Ming Lei <ming....@canonical.com> > >> --- > >> I can reproduce the issue and verify the fix by the following approach: > >> - create one raid1 over two virtio-blk > >> - build bcache device over the above raid1 and another cache device. > >> - set cache mode as writeback > >> - run random write over ext4 on the bcache device > >> - then the crash can be triggered > > > > can you explain why this is better than my original patch? > > Shaohua, your patch is wrong, please see the following link: > > https://lkml.org/lkml/2016/3/30/893
I don't see why, really, except it declares you are right :) why it's 2560 instead of 2048?
