linux-kernel - Non-power-of-2 zone size (was: [PATCH] dm-table:fix zone block

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Message-ID: <c4ee654e-3120-e1a9-80b6-cb7073aa5c1a@redhat.com>
Date: Thu, 4 Jul 2024 21:00:40 +0200 (CEST)
From: Mikulas Patocka <mpatocka@...hat.com>
To: Li Dong <lidong@...o.com>, Damien Le Moal <dlemoal@...nel.org>, 
    Naohiro Aota <naohiro.aota@....com>, Johannes Thumshirn <jth@...nel.org>, 
    Jens Axboe <axboe@...nel.dk>
cc: Alasdair Kergon <agk@...hat.com>, Mike Snitzer <snitzer@...nel.org>, 
    "open list:DEVICE-MAPPER  (LVM)" <dm-devel@...ts.linux.dev>, 
    open list <linux-kernel@...r.kernel.org>, opensource.kernel@...o.com, 
    linux-fsdevel@...r.kernel.org, linux-block@...r.kernel.org
Subject: Non-power-of-2 zone size (was: [PATCH] dm-table:fix zone block_device
 not aligned with zonesize)



> On Thu, 4 Jul 2024, Li Dong wrote:
> 
> > For zone block devices, device_area_is_invalid may return an incorrect 
> > value.
> > 
> > Failure log:
> > [   19.337657]: device-mapper: table: 254:56: len=836960256 not aligned to
> > h/w zone size 3244032 of sde
> > [   19.337665]: device-mapper: core: Cannot calculate initial queue limits
> > [   19.337667]: device-mapper: ioctl: unable to set up device queue for 
> > new table.
> > 
> > Actually, the device's zone length is aligned to the zonesize.
> > 
> > Fixes: 5dea271b6d87 ("dm table: pass correct dev area size to device_area_is_valid")
> > Signed-off-by: Li Dong <lidong@...o.com>
> > ---
> >  drivers/md/dm-table.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
> > index 33b7a1844ed4..0bddae0bee3c 100644
> > --- a/drivers/md/dm-table.c
> > +++ b/drivers/md/dm-table.c
> > @@ -257,7 +257,7 @@ static int device_area_is_invalid(struct dm_target *ti, struct dm_dev *dev,
> >  	if (bdev_is_zoned(bdev)) {
> >  		unsigned int zone_sectors = bdev_zone_sectors(bdev);
> >  
> > -		if (start & (zone_sectors - 1)) {
> > +		if (start % zone_sectors) {
> >  			DMERR("%s: start=%llu not aligned to h/w zone size %u of %pg",
> >  			      dm_device_name(ti->table->md),
> >  			      (unsigned long long)start,
> > @@ -274,7 +274,7 @@ static int device_area_is_invalid(struct dm_target *ti, struct dm_dev *dev,
> >  		 * devices do not end up with a smaller zone in the middle of
> >  		 * the sector range.
> >  		 */
> > -		if (len & (zone_sectors - 1)) {
> > +		if (len % zone_sectors) {
> >  			DMERR("%s: len=%llu not aligned to h/w zone size %u of %pg",
> >  			      dm_device_name(ti->table->md),
> >  			      (unsigned long long)len,
> > -- 
> > 2.31.1.windows.1

I grepped the kernel for bdev_zone_sectors and there are more assumptions 
that bdev_zone_sectors is a power of 2.

drivers/md/dm-zone.c:           sector_t mask = bdev_zone_sectors(disk->part0) - 1
drivers/nvme/target/zns.c:      if (get_capacity(bd_disk) & (bdev_zone_sectors(ns->bdev) - 1))
drivers/nvme/target/zns.c:      if (sect & (bdev_zone_sectors(req->ns->bdev) - 1)) {
fs/zonefs/super.c:      sbi->s_zone_sectors_shift = ilog2(bdev_zone_sectors(sb->s_bdev));
fs/btrfs/zoned.c:       return (sector_t)zone_number << ilog2(bdev_zone_sectors(bdev));
fs/btrfs/zoned.c:	zone_info->zone_size_shift = ilog2(zone_info->zone_size);
include/linux/blkdev.h: return sector & (bdev_zone_sectors(bdev) - 1);
fs/f2fs/super.c:	if (nr_sectors & (zone_sectors - 1))

So, if we want to support non-power-of-2 zone size, we need some 
systematic fix. Now it appears that Linux doesn't even attempt to support 
disks non-power-of-2 zone size.

I added Damien Le Moal so that he can help with testing disks with 
non-power-of-2 zone size (if WD is actually making them).

Mikulas