On 2020/8/4 22:39, Johannes Thumshirn wrote: > On 04/08/2020 16:37, Johannes Thumshirn wrote: >> On 04/08/2020 16:34, Coly Li wrote: >>> On 2020/8/4 22:31, Johannes Thumshirn wrote: >>>> On 04/08/2020 16:23, Coly Li wrote: >>>>> This is the procedure to reproduce the panic, >>>>> # modprobe scsi_debug delay=0 dev_size_mb=2048 max_queue=1 >>>>> # losetup -f /dev/nvme0n1 --direct-io=on >>>>> # blkdiscard /dev/loop0 -o 0 -l 0x200 >>>> >>>> losetup -f /dev/sdX isn't it? >>>> >>> >>> In my case, I use a NVMe SSD as the backing device of the loop device. >>> Because I don't have a scsi lun. >>> >>> And loading scsi_debug module seems necessary, otherwise the discard >>> process just hang and I cannot see the kernel panic (I don't know why yet). >> >> OK, now that's highly interesting. Does it also happen if you back loop with >> a file? loop_config_discard() has different cases for the different backing devices/files. S >> > > Damn I didn't want to hit sent.... > > Does this (untested) change make a difference: > > diff --git a/drivers/block/loop.c b/drivers/block/loop.c > index 475e1a738560..8a07a89d702e 100644 > --- a/drivers/block/loop.c > +++ b/drivers/block/loop.c > @@ -895,6 +895,9 @@ static void loop_config_discard(struct loop_device *lo) > blk_queue_max_write_zeroes_sectors(q, > backingq->limits.max_write_zeroes_sectors); > > + q->limits.discard_granularity = > + backingq->limits.discard_granularity; > + > /* > * We use punch hole to reclaim the free space used by the > * image a.k.a. discard. However we do not support discard if > Yes, Ming just posts a patch with a very similar change to loop device driver. Coly Li
