+CC [jencce.kernel@xxxxxxxxx] > > > 'Murphy Zhou' reports[1] hitting the panic when running xfstests > generic/108 on pmem ramdisk. In his words: > > This test is simulating partial disk error when calling fsync(): > create a lvm vg which consists of 2 disks: > one scsi_debug disk; one other disk I specified, pmem ramdisk in this > case. > create lv in this vg and write to it, make sure writing across 2 disks; > offline scsi_debug disk; > write again to allocated area; > expect fsync: IO error. > If one of the disks is pmem ramdisk, it reproduces every time on my setup, > on v5.3-rc2+. > The mount -o dax option is not required to reproduce this panic. > ... > > Fix this by returning false from 'device_synchronous' function when dax_dev > is NULL. > > [ 1984.878208] BUG: kernel NULL pointer dereference, address: > 00000000000002d0 > [ 1984.882546] #PF: supervisor read access in kernel mode > [ 1984.885664] #PF: error_code(0x0000) - not-present page > [ 1984.888626] PGD 0 P4D 0 > [ 1984.890140] Oops: 0000 [#1] SMP PTI > ... > ... > [ 1984.943682] Call Trace: > [ 1984.945007] device_synchronous+0xe/0x20 [dm_mod] > [ 1984.947328] stripe_iterate_devices+0x48/0x60 [dm_mod] > [ 1984.949947] ? dm_set_device_limits+0x130/0x130 [dm_mod] > [ 1984.952516] dm_table_supports_dax+0x39/0x90 [dm_mod] > [ 1984.954989] dm_table_set_restrictions+0x248/0x5d0 [dm_mod] > [ 1984.957685] dm_setup_md_queue+0x66/0x110 [dm_mod] > [ 1984.960280] table_load+0x1e3/0x390 [dm_mod] > [ 1984.962491] ? retrieve_status+0x1c0/0x1c0 [dm_mod] > [ 1984.964910] ctl_ioctl+0x1d3/0x550 [dm_mod] > [ 1984.967006] ? path_lookupat+0xf4/0x200 > [ 1984.968890] dm_ctl_ioctl+0xa/0x10 [dm_mod] > [ 1984.970920] do_vfs_ioctl+0xa9/0x630 > [ 1984.972701] ksys_ioctl+0x60/0x90 > [ 1984.974335] __x64_sys_ioctl+0x16/0x20 > [ 1984.976221] do_syscall_64+0x5b/0x1d0 > [ 1984.978091] entry_SYSCALL_64_after_hwframe+0x44/0xa9 > > [1] > https://lore.kernel.org/linux-fsdevel/2011806368.5335560.1564469373050.JavaMail.zimbra@xxxxxxxxxx/T/#mac662eb50b9d7bd282b23e6e8625a3f7a4687506 > > Fixes: 2e9ee0955d3c ("dm: enable synchronous dax") > Reported-by: jencce.kernel@xxxxxxxxx > Tested-by: jencce.kernel@xxxxxxxxx > Signed-off-by: Pankaj Gupta <pagupta@xxxxxxxxxx> > --- > drivers/md/dm-table.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c > index caaee8032afe..b065845c1bdd 100644 > --- a/drivers/md/dm-table.c > +++ b/drivers/md/dm-table.c > @@ -894,6 +894,9 @@ int device_supports_dax(struct dm_target *ti, struct > dm_dev *dev, > static int device_synchronous(struct dm_target *ti, struct dm_dev *dev, > sector_t start, sector_t len, void *data) > { > + if (!dev->dax_dev) > + return false; > + > return dax_synchronous(dev->dax_dev); > } > > -- > 2.20.1 > > -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
