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-kernelorg@xxxxxxxxxxxxxxxxx> > Reported-by: Eric Wheeler <bcache@xxxxxxxxxxxxxxxxxx> > Cc: stable@xxxxxxxxxxxxxxx (4.2+) > Cc: Shaohua Li <shli@xxxxxx> > Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxxxxx> > --- > 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? -- To unsubscribe from this list: send the line "unsubscribe linux-block" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
