-----Original Message----- From: Dan Williams dan.j.williams@intel.com Sent: Saturday, September 19, 2020 3:51 AM To: dm-devel@redhat.com Cc: stable@vger.kernel.org; Jan Kara jack@suse.cz; Alasdair Kergon agk@redhat.com; Mike Snitzer snitzer@redhat.com; Adrian Huang12 ahuang12@lenovo.com; linux-nvdimm@lists.01.org; linux- kernel@vger.kernel.org Subject: [External] [PATCH] dm/dax: Fix table reference counts
A recent fix to the dm_dax_supported() flow uncovered a latent bug. When dm_get_live_table() fails it is still required to drop the srcu_read_lock(). Without this change the lvm2 test-suite triggers this warning:
# lvm2-testsuite --only pvmove-abort-all.sh WARNING: lock held when returning to user space! 5.9.0-rc5+ #251 Tainted: G OE ------------------------------------------------ lvm/1318 is leaving the kernel with locks still held! 1 lock held by lvm/1318: #0: ffff9372abb5a340 (&md->io_barrier){....}-{0:0}, at:dm_get_live_table+0x5/0xb0 [dm_mod]
...and later on this hang signature:
INFO: task lvm:1344 blocked for more than 122 seconds. Tainted: G OE 5.9.0-rc5+ #251 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:lvm state:D stack: 0 pid: 1344 ppid: 1 flags:0x00004000 Call Trace: __schedule+0x45f/0xa80 ? finish_task_switch+0x249/0x2c0 ? wait_for_completion+0x86/0x110 schedule+0x5f/0xd0 schedule_timeout+0x212/0x2a0 ? __schedule+0x467/0xa80 ? wait_for_completion+0x86/0x110 wait_for_completion+0xb0/0x110 __synchronize_srcu+0xd1/0x160 ? __bpf_trace_rcu_utilization+0x10/0x10 __dm_suspend+0x6d/0x210 [dm_mod] dm_suspend+0xf6/0x140 [dm_mod]Fixes: 7bf7eac8d648 ("dax: Arrange for dax_supported check to span multiple devices") Cc: stable@vger.kernel.org Cc: Jan Kara jack@suse.cz Cc: Alasdair Kergon agk@redhat.com Cc: Mike Snitzer snitzer@redhat.com Reported-by: Adrian Huang ahuang12@lenovo.com Signed-off-by: Dan Williams dan.j.williams@intel.com
Cool, thanks for the fix. This solves the issue.
Tested-by: Adrian Huang ahuang12@lenovo.com
drivers/md/dm.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/drivers/md/dm.c b/drivers/md/dm.c index fb0255d25e4b..4a40df8af7d3 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -1136,15 +1136,16 @@ static bool dm_dax_supported(struct dax_device *dax_dev, struct block_device *bd { struct mapped_device *md = dax_get_private(dax_dev); struct dm_table *map;
- bool ret = false; int srcu_idx;
bool ret;
map = dm_get_live_table(md, &srcu_idx); if (!map)
return false;
goto out;ret = dm_table_supports_dax(map, device_supports_dax, &blocksize);
+out: dm_put_live_table(md, srcu_idx);
return ret;