Re: [PATCH 4/6] xfs: fix zero byte checking in the superblock scrubber

On Tue, Dec 03, 2024 at 07:03:16PM -0800, Darrick J. Wong wrote:

+/* Calculate the ondisk superblock size in bytes */ +STATIC size_t +xchk_superblock_ondisk_size(

• struct xfs_mount *mp)

+{

• if (xfs_has_metadir(mp))

• return offsetofend(struct xfs_dsb, sb_pad);
  

• if (xfs_has_metauuid(mp))

• return offsetofend(struct xfs_dsb, sb_meta_uuid);
  

• if (xfs_has_crc(mp))

• return offsetofend(struct xfs_dsb, sb_lsn);
  

• if (xfs_sb_version_hasmorebits(&mp->m_sb))

• return offsetofend(struct xfs_dsb, sb_bad_features2);
  

• if (xfs_has_logv2(mp))

• return offsetofend(struct xfs_dsb, sb_logsunit);
  

• if (xfs_has_sector(mp))

• return offsetofend(struct xfs_dsb, sb_logsectsize);
  

• /* only support dirv2 or more recent */
• return offsetofend(struct xfs_dsb, sb_dirblklog);

This really should be libxfs so tht it can be shared with secondary_sb_whack in xfsrepair. The comment at the end of the xfs_dsb definition should also be changed to point to this libxfs version.

+} /* Everything else must be zero. */

• if (memchr_inv(sb + 1, 0,

• 	BBTOB(bp->b_length) - sizeof(struct xfs_dsb)))
  

• sblen = xchk_superblock_ondisk_size(mp);
• if (memchr_inv((char *)sb + sblen, 0, BBTOB(bp->b_length) - sblen))

This could be simplified to

if (memchr_inv(bp->b_addr + sblen, 0, BBTOB(bp->b_length) - sblen))

Otherwise looks good:

Reviewed-by: Christoph Hellwig hch@lst.de