md/raid5: limit request size according to implementation limits
authorKonstantin Khlebnikov <khlebnikov@yandex-team.ru>
Sun, 27 Nov 2016 16:32:32 +0000 (19:32 +0300)
committerShaohua Li <shli@fb.com>
Tue, 29 Nov 2016 23:53:21 +0000 (15:53 -0800)
commite8d7c33232e5fdfa761c3416539bc5b4acd12db5
treedf0f691267ac01dfd9d2c52cba92a13354cab646
parent1a0ec5c30c37d29e4435a45e75c896f91af970bd
md/raid5: limit request size according to implementation limits

Current implementation employ 16bit counter of active stripes in lower
bits of bio->bi_phys_segments. If request is big enough to overflow
this counter bio will be completed and freed too early.

Fortunately this not happens in default configuration because several
other limits prevent that: stripe_cache_size * nr_disks effectively
limits count of active stripes. And small max_sectors_kb at lower
disks prevent that during normal read/write operations.

Overflow easily happens in discard if it's enabled by module parameter
"devices_handle_discard_safely" and stripe_cache_size is set big enough.

This patch limits requests size with 256Mb - 8Kb to prevent overflows.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Cc: Shaohua Li <shli@kernel.org>
Cc: Neil Brown <neilb@suse.com>
Cc: stable@vger.kernel.org
Signed-off-by: Shaohua Li <shli@fb.com>
drivers/md/raid5.c