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

[Karel Zak <kzak@redhat.com>]

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.

> +
> +#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()

 ...
> +		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.

> +			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().

> +	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;
   }
 }




 Karel

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