When there are no paths and multipath receives an ioctl, it waits until
a path becomes available. This behaviour is incorrect if the
"queue_if_no_path" setting was not specified, as then the ioctl should
be rejected immediately, which this patch now does.
commit 35991652b ("dm mpath: allow ioctls to trigger pg init") should
have checked if queue_if_no_path was configured before queueing IO.
Checking for the queue_if_no_path feature, like is done in map_io(),
allows the following table load to work without blocking in the
multipath_ioctl retry loop:
echo "0 1024 multipath 0 0 0 0" | dmsetup create mpath_nodevs
Without this fix the multipath_ioctl will block with the following stack
trace:
blkid D 0000000000000002 0 23936 1 0x00000000
ffff8802b89e5cd8 0000000000000082 ffff8802b89e5fd8 0000000000012440
ffff8802b89e4010 0000000000012440 0000000000012440 0000000000012440
ffff8802b89e5fd8 0000000000012440 ffff88030c2aab30 ffff880325794040
Call Trace:
[<ffffffff814ce099>] schedule+0x29/0x70
[<ffffffff814cc312>] schedule_timeout+0x182/0x2e0
[<ffffffff8104dee0>] ? lock_timer_base+0x70/0x70
[<ffffffff814cc48e>] schedule_timeout_uninterruptible+0x1e/0x20
[<ffffffff8104f840>] msleep+0x20/0x30
[<ffffffffa0000839>] multipath_ioctl+0x109/0x170 [dm_multipath]
[<ffffffffa06bfb9c>] dm_blk_ioctl+0xbc/0xd0 [dm_mod]
[<ffffffff8122a408>] __blkdev_driver_ioctl+0x28/0x30
[<ffffffff8122a79e>] blkdev_ioctl+0xce/0x730
[<ffffffff811970ac>] block_ioctl+0x3c/0x40
[<ffffffff8117321c>] do_vfs_ioctl+0x8c/0x340
[<ffffffff81166293>] ? sys_newfstat+0x33/0x40
[<ffffffff81173571>] sys_ioctl+0xa1/0xb0
[<ffffffff814d70a9>] system_call_fastpath+0x16/0x1b
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org # 3.5+
Acked-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
7ba10aa6fb