diff options
author | Kiyoshi Ueda <k-ueda@ct.jp.nec.com> | 2010-02-16 18:43:01 +0000 |
---|---|---|
committer | Alasdair G Kergon <agk@redhat.com> | 2010-02-16 18:43:01 +0000 |
commit | 9eef87da2a8ea4920e0d913ff977cac064b68ee0 (patch) | |
tree | 811eb358ce2fa66517b0cf59501522c17dfbe6bc /kernel/lockdep.c | |
parent | 558569aa9d83e016295bac77d900342908d7fd85 (diff) | |
download | kernel_samsung_crespo-9eef87da2a8ea4920e0d913ff977cac064b68ee0.zip kernel_samsung_crespo-9eef87da2a8ea4920e0d913ff977cac064b68ee0.tar.gz kernel_samsung_crespo-9eef87da2a8ea4920e0d913ff977cac064b68ee0.tar.bz2 |
dm mpath: fix stall when requeueing io
This patch fixes the problem that system may stall if target's ->map_rq
returns DM_MAPIO_REQUEUE in map_request().
E.g. stall happens on 1 CPU box when a dm-mpath device with queue_if_no_path
bounces between all-paths-down and paths-up on I/O load.
When target's ->map_rq returns DM_MAPIO_REQUEUE, map_request() requeues
the request and returns to dm_request_fn(). Then, dm_request_fn()
doesn't exit the I/O dispatching loop and continues processing
the requeued request again.
This map and requeue loop can be done with interrupt disabled,
so 1 CPU system can be stalled if this situation happens.
For example, commands below can stall my 1 CPU box within 1 minute or so:
# dmsetup table mp
mp: 0 2097152 multipath 1 queue_if_no_path 0 1 1 service-time 0 1 2 8:144 1 1
# while true; do dd if=/dev/mapper/mp of=/dev/null bs=1M count=100; done &
# while true; do \
> dmsetup message mp 0 "fail_path 8:144" \
> dmsetup suspend --noflush mp \
> dmsetup resume mp \
> dmsetup message mp 0 "reinstate_path 8:144" \
> done
To fix the problem above, this patch changes dm_request_fn() to exit
the I/O dispatching loop once if a request is requeued in map_request().
Signed-off-by: Kiyoshi Ueda <k-ueda@ct.jp.nec.com>
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Cc: stable@kernel.org
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Diffstat (limited to 'kernel/lockdep.c')
0 files changed, 0 insertions, 0 deletions