On 18.06.2021 01.03, Ming Lei wrote:

On Fri, Jun 18, 2021 at 12:11:57AM +0200, Kristian Klausen wrote:

Commit log?

I will try to come up with a commit message. AFAIU the missing call to loop_config_discard() causes the block device to report "no discard support" (best-case) or stale/incorrect discard support (ex: if the loop device was configured with LOOP_SET_STATUS(64) and later LOOP_CONFIGURE).

...

Cc: stable@vger.kernel.org # 5.8.x- Fixes: 3448914e8cc5 ("loop: Add LOOP_CONFIGURE ioctl") Signed-off-by: Kristian Klausen kristian@klausen.dk

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Tested like so (without the patch): losetup 2.37<= uses LOOP_CONFIGURE instead of LOOP_SET_STATUS64[1]

# fallocate -l100M disk.img # rmmod loop # losetup --version losetup from util-linux 2.36.2 # losetup --find --show disk.img /dev/loop0 # grep '' /sys/devices/virtual/block/loop0/queue/*discard* /sys/devices/virtual/block/loop0/queue/discard_granularity:4096 /sys/devices/virtual/block/loop0/queue/discard_max_bytes:4294966784 /sys/devices/virtual/block/loop0/queue/discard_max_hw_bytes:4294966784 /sys/devices/virtual/block/loop0/queue/discard_zeroes_data:0 /sys/devices/virtual/block/loop0/queue/max_discard_segments:1 # losetup -d /dev/loop0 # [update util-linux] # losetup --version losetup from util-linux 2.37 # rmmod loop # losetup --find --show disk.img /dev/loop0 # grep '' /sys/devices/virtual/block/loop0/queue/*discard* /sys/devices/virtual/block/loop0/queue/discard_granularity:0 /sys/devices/virtual/block/loop0/queue/discard_max_bytes:0 /sys/devices/virtual/block/loop0/queue/discard_max_hw_bytes:0 /sys/devices/virtual/block/loop0/queue/discard_zeroes_data:0 /sys/devices/virtual/block/loop0/queue/max_discard_segments:1

With the patch applied:

# losetup --version losetup from util-linux 2.37 # rmmod loop # losetup --find --show disk.img /dev/loop0 # grep '' /sys/devices/virtual/block/loop0/queue/*discard* /sys/devices/virtual/block/loop0/queue/discard_granularity:4096 /sys/devices/virtual/block/loop0/queue/discard_max_bytes:4294966784 /sys/devices/virtual/block/loop0/queue/discard_max_hw_bytes:4294966784 /sys/devices/virtual/block/loop0/queue/discard_zeroes_data:0 /sys/devices/virtual/block/loop0/queue/max_discard_segments:1

[1] https://github.com/karelzak/util-linux/pull/1152

drivers/block/loop.c | 2 ++ 1 file changed, 2 insertions(+)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c index 76e12f3482a9..ec957f6d8a49 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -1168,6 +1168,8 @@ static int loop_configure(struct loop_device *lo, fmode_t mode, if (partscan) lo->lo_disk->flags &= ~GENHD_FL_NO_PART_SCAN;

• loop_config_discard(lo);

It could be better to move loop_config_discard() around loop_update_rotational/loop_update_dio(), then we setup everything before updating loop as Lo_bound.

I will move it before loop_update_rotational().

Otherwise, this patch looks fine.

Thanks, Ming