On Thu 27-09-18 11:22:22, Dan Williams wrote: > On Thu, Sep 27, 2018 at 6:41 AM Jan Kara <jack@xxxxxxx> wrote: > > > > On Thu 27-09-18 06:28:43, Matthew Wilcox wrote: > > > On Thu, Sep 27, 2018 at 01:23:32PM +0200, Jan Kara wrote: > > > > When dax_lock_mapping_entry() has to sleep to obtain entry lock, it will > > > > fail to unlock mapping->i_pages spinlock and thus immediately deadlock > > > > against itself when retrying to grab the entry lock again. Fix the > > > > problem by unlocking mapping->i_pages before retrying. > > > > > > It seems weird that xfstests doesn't provoke this ... > > > > The function currently gets called only from mm/memory-failure.c. And yes, > > we are lacking DAX hwpoison error tests in fstests... > > I have an item on my backlog to port the ndctl unit test that does > memory_failure() injection vs ext4 over to fstests. That said I've > been investigating a deadlock on ext4 caused by this test. When I saw > this patch I hoped it was root cause, but the test is still failing > for me. Vishal is able to pass the test on his system, so the failure > mode is timing dependent. I'm running this patch on top of -rc5 and > still seeing the following deadlock. I went through the code but I don't see where the problem could be. How can I run that test? Is KVM enough or do I need hardware with AEP dimms? Honza > > EXT4-fs (pmem0): DAX enabled. Warning: EXPERIMENTAL, use at your own risk > EXT4-fs (pmem0): mounted filesystem with ordered data mode. Opts: dax > Injecting memory failure for pfn 0x208900 at process virtual > address 0x7f5872900000 > Memory failure: 0x208900: Killing dax-pmd:7095 due to hardware > memory corruption > Memory failure: 0x208900: recovery action for dax page: Recovered > watchdog: BUG: soft lockup - CPU#35 stuck for 22s! [dax-pmd:7095] > [..] > irq event stamp: 121911146 > hardirqs last enabled at (121911145): [<ffffffff81aa1bd9>] > _raw_spin_unlock_irq+0x29/0x40 hardirqs last disabled at > (121911146): [<ffffffff810037a3>] trace_hardirqs_off_thunk+0x1a/0x1c > softirqs last enabled at (78238674): [<ffffffff81e0032e>] > __do_softirq+0x32e/0x428 > softirqs last disabled at (78238627): [<ffffffff810bc6f6>] > irq_exit+0xf6/0x100 > CPU: 35 PID: 7095 Comm: dax-pmd Tainted: G OE > 4.19.0-rc5+ #2394 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS > rel-1.11.1-0-g0551a4be2c-prebuilt.qemu-project.org 04/01/2014 > RIP: 0010:lock_release+0x134/0x2a0 > [..] > Call Trace: > find_get_entries+0x299/0x3c0 > pagevec_lookup_entries+0x1a/0x30 > dax_layout_busy_page+0x9c/0x280 > ? __lock_acquire+0x12fa/0x1310 > ext4_break_layouts+0x48/0x100 > ? ext4_punch_hole+0x108/0x5a0 > ext4_punch_hole+0x110/0x5a0 > ext4_fallocate+0x189/0xa40 > ? rcu_read_lock_sched_held+0x6b/0x80 > ? rcu_sync_lockdep_assert+0x2e/0x60 > vfs_fallocate+0x13f/0x270 > > The same test against xfs is not failing for me. I have been seeking > some focus time to dig in on this. -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
