On Mon, Apr 29, 2019 at 02:05:42PM +0200, Salvatore Bonaccorso wrote: > Hi Jan, hi Greg, > > On Wed, Mar 20, 2019 at 01:58:06PM +0100, Jan Kara wrote: > > Hello, > > > > commit 310ca162d77 "block/loop: Use global lock for ioctl() operation." has > > been pushed to multiple stable trees. This patch is a part of larger series > > that overhauls the locking inside loopback device upstream and for 4.4, > > 4.9, and 4.14 stable trees only this patch from the series is applied. Our > > testing now has shown [1] that the patch alone makes present deadlocks > > inside loopback driver more likely (the openqa test in our infrastructure > > didn't hit the deadlock before whereas with the new kernel it hits it > > reliably every time). So I would suggest we revert 310ca162d77 from 4.4, > > 4.9, and 4.14 kernels. > > A user in Debian reported [1], providing the following testcase which showed up > after the recent update to 4.9.168-1 in Debian stretch (based on upstream > v4.9.168) as follows: > > dd if=/dev/zero of=/tmp/ff1.raw bs=1G seek=8 count=0 > sync > sleep 1 > parted /tmp/ff1.raw mklabel msdos > parted -s /tmp/ff1.raw mkpart primary linux-swap 1 100 > parted -s -- /tmp/ff1.raw mkpart primary ext2 101 -1 > parted -s -- /tmp/ff1.raw set 2 boot on > sleep 5 > losetup -Pf /tmp/ff1.raw --show > > I have verified that the same happens with v4.9.171 where the mentioned commit > was not reverted, and bisecting of the testcase showed it was introduced with > 3ae3d167f5ec2c7bb5fcd12b7772cfadc93b2305 (v4.9.152~9) (which is the backport of > 310ca162d77 for 4.9). > > Reverting 3ae3d167f5ec2c7bb5fcd12b7772cfadc93b2305 on top of v4.9.171 worked > and fixed the respective issue. > > Can this commit in meanwhile be reverted or is there further ongoing work in > integrating the followup fixes as mentioned in > https://lore.kernel.org/stable/20190321104110.GF29086@xxxxxxxxxxxxxx/ . Sorry for the delay here. No, I didn't find any time for the followup stuff here, and Jan is right, this should just be dropped. I've now reverted it from 3.18.y, 4.4.y, 4.9.y, and 4.14.y. thanks, greg k-h
