Re: [PATCH v2 2/3] blkid: add magic and probing for zoned btrfs

[Naohiro Aota <naohiro.aota@wdc.com>]

On Wed, Apr 14, 2021 at 03:47:08PM +0200, Karel Zak wrote:
> On Wed, Apr 14, 2021 at 10:33:38AM +0900, Naohiro Aota wrote:
> > +#define ASSERT(x) assert(x)
> 
> Really? ;-)
> 
> > +typedef uint64_t u64;
> > +typedef uint64_t sector_t;
> > +typedef uint8_t u8;
> 
> I do not see a reason for u64 and u8 here.

Yep, these are here just to make it easy to copy the code from
kernel. But this code won't change so much, so I can drop these.

> > +
> > +#ifdef HAVE_LINUX_BLKZONED_H
> > +static int sb_write_pointer(int fd, struct blk_zone *zones, u64 *wp_ret)
> > +{
> > +	bool empty[BTRFS_NR_SB_LOG_ZONES];
> > +	bool full[BTRFS_NR_SB_LOG_ZONES];
> > +	sector_t sector;
> > +
> > +	ASSERT(zones[0].type != BLK_ZONE_TYPE_CONVENTIONAL &&
> > +	       zones[1].type != BLK_ZONE_TYPE_CONVENTIONAL);
> 
> assert()

I will use it.

>  ...
> > +		for (i = 0; i < BTRFS_NR_SB_LOG_ZONES; i++) {
> > +			u64 bytenr;
> > +
> > +			bytenr = ((zones[i].start + zones[i].len)
> > +				   << SECTOR_SHIFT) - BTRFS_SUPER_INFO_SIZE;
> > +
> > +			ret = pread64(fd, buf[i], BTRFS_SUPER_INFO_SIZE,
> > +				      bytenr);
> 
>  please, use  
> 
>      ptr = blkid_probe_get_buffer(pr, BTRFS_SUPER_INFO_SIZE, bytenr);
> 
>  the library will care about the buffer and reuse it. It's also
>  important to keep blkid_do_wipe() usable.

Sure. I'll use it.

> > +			if (ret != BTRFS_SUPER_INFO_SIZE)
> > +				return -EIO;
> > +			super[i] = (struct btrfs_super_block *)&buf[i];
> 
>   super[i] = (struct btrfs_super_block *) ptr;
> 
> > +		}
> > +
> > +		if (super[0]->generation > super[1]->generation)
> > +			sector = zones[1].start;
> > +		else
> > +			sector = zones[0].start;
> > +	} else if (!full[0] && (empty[1] || full[1])) {
> > +		sector = zones[0].wp;
> > +	} else if (full[0]) {
> > +		sector = zones[1].wp;
> > +	} else {
> > +		return -EUCLEAN;
> > +	}
> > +	*wp_ret = sector << SECTOR_SHIFT;
> > +	return 0;
> > +}
> > +
> > +static int sb_log_offset(blkid_probe pr, uint64_t *bytenr_ret)
> > +{
> > +	uint32_t zone_num = 0;
> > +	uint32_t zone_size_sector;
> > +	struct blk_zone_report *rep;
> > +	struct blk_zone *zones;
> > +	size_t rep_size;
> > +	int ret;
> > +	uint64_t wp;
> > +
> > +	zone_size_sector = pr->zone_size >> SECTOR_SHIFT;
> > +
> > +	rep_size = sizeof(struct blk_zone_report) + sizeof(struct blk_zone) * 2;
> > +	rep = malloc(rep_size);
> > +	if (!rep)
> > +		return -errno;
> > +
> > +	memset(rep, 0, rep_size);
> > +	rep->sector = zone_num * zone_size_sector;
> > +	rep->nr_zones = 2;
> 
> what about to add to lib/blkdev.c a new function:
> 
>    struct blk_zone_report *blkdev_get_zonereport(int fd, uint64 sector, int nzones);
> 
> and call this function from your sb_log_offset() as well as from blkid_do_wipe()?
> 
> Anyway, calloc() is better than malloc()+memset().

Indeed. I will do so.

> > +	if (zones[0].type == BLK_ZONE_TYPE_CONVENTIONAL) {
> > +		*bytenr_ret = zones[0].start << SECTOR_SHIFT;
> > +		ret = 0;
> > +		goto out;
> > +	} else if (zones[1].type == BLK_ZONE_TYPE_CONVENTIONAL) {
> > +		*bytenr_ret = zones[1].start << SECTOR_SHIFT;
> > +		ret = 0;
> > +		goto out;
> > +	}
> 
> what about:
> 
>  for (i = 0; i < BTRFS_NR_SB_LOG_ZONES; i++) {
>    if (zones[i].type == BLK_ZONE_TYPE_CONVENTIONAL) {
>       *bytenr_ret = zones[i].start << SECTOR_SHIFT;
>       ret = 0;
>       goto out;
>    }
>  }

Yes, this looks cleaner. Thanks.

> 
> 
> 
>  Karel
> 
> -- 
>  Karel Zak  <kzak@redhat.com>
>  http://karelzak.blogspot.com
>