Messages in this thread | | | Date | Wed, 11 May 2022 16:39:17 +0200 | Subject | Re: [PATCH v3 11/11] dm-zoned: ensure only power of 2 zone sizes are allowed | From | Pankaj Raghav <> |
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Hi David,
On 2022-05-09 20:54, David Sterba wrote:>> diff --git a/drivers/md/dm-zone.c b/drivers/md/dm-zone.c >> index 3e7b1fe15..27dc4ddf2 100644 >> --- a/drivers/md/dm-zone.c >> +++ b/drivers/md/dm-zone.c >> @@ -231,6 +231,18 @@ static int dm_revalidate_zones(struct mapped_device *md, struct dm_table *t) >> struct request_queue *q = md->queue; >> unsigned int noio_flag; >> int ret; >> + struct block_device *bdev = md->disk->part0; >> + sector_t zone_sectors; >> + char bname[BDEVNAME_SIZE]; >> + >> + zone_sectors = bdev_zone_sectors(bdev); >> + >> + if (!is_power_of_2(zone_sectors)) { > > is_power_of_2 takes 'unsigned long' and sector_t is u64, so this is not > 32bit clean and we had an actual bug where value 1<<48 was not > recognized as power of 2. > Good catch. Now I understand why btrfs has a helper for is_power_of_two_u64.
But the zone size can never be more than 32bit value so the zone size sect will never greater than unsigned long.
With that said, we have two options:
1.) We can put a comment explaining that even though it is 32 bit unsafe, zone size sect can never be a 32bit value
or
2) We should move the btrfs only helper `is_power_of_two_u64` to some common header and use it everywhere.
Let me know your thoughts.
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