4.4-stable review patch. If anyone has any objections, please let me know.
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From: Alan Jenkins alan.christopher.jenkins@gmail.com
commit 1dc3039bc87ae7d19a990c3ee71cfd8a9068f428 upstream.
When blk_queue_enter() waits for a queue to unfreeze, or unset the PREEMPT_ONLY flag, do not allow it to be interrupted by a signal.
The PREEMPT_ONLY flag was introduced later in commit 3a0a529971ec ("block, scsi: Make SCSI quiesce and resume work reliably"). Note the SCSI device is resumed asynchronously, i.e. after un-freezing userspace tasks.
So that commit exposed the bug as a regression in v4.15. A mysterious SIGBUS (or -EIO) sometimes happened during the time the device was being resumed. Most frequently, there was no kernel log message, and we saw Xorg or Xwayland killed by SIGBUS.[1]
[1] E.g. https://bugzilla.redhat.com/show_bug.cgi?id=1553979
Without this fix, I get an IO error in this test:
# dd if=/dev/sda of=/dev/null iflag=direct & \ while killall -SIGUSR1 dd; do sleep 0.1; done & \ echo mem > /sys/power/state ; \ sleep 5; killall dd # stop after 5 seconds
The interruptible wait was added to blk_queue_enter in commit 3ef28e83ab15 ("block: generic request_queue reference counting"). Before then, the interruptible wait was only in blk-mq, but I don't think it could ever have been correct.
Reviewed-by: Bart Van Assche bart.vanassche@wdc.com Cc: stable@vger.kernel.org Signed-off-by: Alan Jenkins alan.christopher.jenkins@gmail.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Sudip Mukherjee sudipm.mukherjee@gmail.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- block/blk-core.c | 10 +++------- 1 file changed, 3 insertions(+), 7 deletions(-)
--- a/block/blk-core.c +++ b/block/blk-core.c @@ -651,21 +651,17 @@ EXPORT_SYMBOL(blk_alloc_queue); int blk_queue_enter(struct request_queue *q, gfp_t gfp) { while (true) { - int ret; - if (percpu_ref_tryget_live(&q->q_usage_counter)) return 0;
if (!gfpflags_allow_blocking(gfp)) return -EBUSY;
- ret = wait_event_interruptible(q->mq_freeze_wq, - !atomic_read(&q->mq_freeze_depth) || - blk_queue_dying(q)); + wait_event(q->mq_freeze_wq, + !atomic_read(&q->mq_freeze_depth) || + blk_queue_dying(q)); if (blk_queue_dying(q)) return -ENODEV; - if (ret) - return ret; } }