Commit 7ba10aa6 authored by Mike Snitzer's avatar Mike Snitzer Committed by Alasdair G Kergon

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 35991652 ("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: default avatarMike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org # 3.5+
Acked-by: default avatarMikulas Patocka <mpatocka@redhat.com>
Signed-off-by: default avatarAlasdair G Kergon <agk@redhat.com>
parent 307615a2
...@@ -1555,6 +1555,7 @@ static int multipath_ioctl(struct dm_target *ti, unsigned int cmd, ...@@ -1555,6 +1555,7 @@ static int multipath_ioctl(struct dm_target *ti, unsigned int cmd,
unsigned long arg) unsigned long arg)
{ {
struct multipath *m = ti->private; struct multipath *m = ti->private;
struct pgpath *pgpath;
struct block_device *bdev; struct block_device *bdev;
fmode_t mode; fmode_t mode;
unsigned long flags; unsigned long flags;
...@@ -1570,12 +1571,14 @@ static int multipath_ioctl(struct dm_target *ti, unsigned int cmd, ...@@ -1570,12 +1571,14 @@ static int multipath_ioctl(struct dm_target *ti, unsigned int cmd,
if (!m->current_pgpath) if (!m->current_pgpath)
__choose_pgpath(m, 0); __choose_pgpath(m, 0);
if (m->current_pgpath) { pgpath = m->current_pgpath;
bdev = m->current_pgpath->path.dev->bdev;
mode = m->current_pgpath->path.dev->mode; 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; r = -EAGAIN;
else if (!bdev) else if (!bdev)
r = -EIO; r = -EIO;
......
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