From 7ba10aa6fbac7158a50bec142132b04bc480bb29 Mon Sep 17 00:00:00 2001 From: Mike Snitzer Date: Wed, 26 Sep 2012 23:45:41 +0100 Subject: [PATCH] dm mpath: only retry ioctl when no paths if queue_if_no_path set 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: [] schedule+0x29/0x70 [] schedule_timeout+0x182/0x2e0 [] ? lock_timer_base+0x70/0x70 [] schedule_timeout_uninterruptible+0x1e/0x20 [] msleep+0x20/0x30 [] multipath_ioctl+0x109/0x170 [dm_multipath] [] dm_blk_ioctl+0xbc/0xd0 [dm_mod] [] __blkdev_driver_ioctl+0x28/0x30 [] blkdev_ioctl+0xce/0x730 [] block_ioctl+0x3c/0x40 [] do_vfs_ioctl+0x8c/0x340 [] ? sys_newfstat+0x33/0x40 [] sys_ioctl+0xa1/0xb0 [] system_call_fastpath+0x16/0x1b Signed-off-by: Mike Snitzer Cc: stable@vger.kernel.org # 3.5+ Acked-by: Mikulas Patocka Signed-off-by: Alasdair G Kergon --- drivers/md/dm-mpath.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c index d8abb90a6c2f..034233eefc82 100644 --- a/drivers/md/dm-mpath.c +++ b/drivers/md/dm-mpath.c @@ -1555,6 +1555,7 @@ static int multipath_ioctl(struct dm_target *ti, unsigned int cmd, unsigned long arg) { struct multipath *m = ti->private; + struct pgpath *pgpath; struct block_device *bdev; fmode_t mode; unsigned long flags; @@ -1570,12 +1571,14 @@ again: if (!m->current_pgpath) __choose_pgpath(m, 0); - if (m->current_pgpath) { - bdev = m->current_pgpath->path.dev->bdev; - mode = m->current_pgpath->path.dev->mode; + pgpath = m->current_pgpath; + + if (pgpath) { + bdev = pgpath->path.dev->bdev; + mode = pgpath->path.dev->mode; } - if (m->queue_io) + if ((pgpath && m->queue_io) || (!pgpath && m->queue_if_no_path)) r = -EAGAIN; else if (!bdev) r = -EIO; -- 2.20.1