| Message ID | 160045867590.25663.7548541079217827340.stgit@dwillia2-desk3.amr.corp.intel.com |
|---|---|
| State | New |
| Headers | show |
| Series | dm/dax: Fix table reference counts | expand |
> -----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;
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;
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> --- drivers/md/dm.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)