On Sat, Sep 08 2012 at 12:50pm -0400, Mikulas Patocka <mpatocka@xxxxxxxxxx> wrote: > It's hard to say what should be done correctly ... if you create a > multipath device with "queue_if_no_path" and no active path, it should > delay all requests until a path becomes available ... and it is doing > that. > > Maybe we could move the waiting loop up to dm_blk_ioctl so that it unlocks > when someone reloads the target? I think it much more likely that multipathd will restore a path then an entirely new table be loaded. > BTW. there is also -EAGAIN dm_blk_ioctl if dm_suspended_md ... should this > -EAGAIN be removed too or not? Don't think it needs to be removed. Here is a patch that addresses the issue for me. --- From: Mike Snitzer <snitzer@xxxxxxxxxx> Subject: [PATCH] dm mpath: only retry ioctl if queue_if_no_path was configured 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@xxxxxxxxxx> --- drivers/md/dm-mpath.c | 11 +++++++---- 1 files changed, 7 insertions(+), 4 deletions(-) diff --git a/drivers/md/dm-mpath.c b/drivers/md/dm-mpath.c index d8abb90..034233e 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; -- 1.7.1 -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel