Re: [PATCH 30/32] xfs_db: support RT data checksum

["Darrick J. Wong" <djwong@kernel.org>]

On Sat, Sep 26, 2026 at 08:21:15AM +0200, Christoph Hellwig wrote:
> On Fri, Sep 25, 2026 at 04:43:58PM -0700, Darrick J. Wong wrote:
> > > +	{ "csums", FLDT_SUMINFO, OI(bitize(sizeof(struct xfs_rtbuf_blkinfo))),
> > 
> > FLDT_SUMINFO is 4 bytes, this won't work for crc64.
> 
> Ouch, yes.
> 
> > You might want to add a FLDT_CRC32C and FLDT_CRC64 so that the sizes can
> > be correct, db can convert them from big-endian to host for display, and
> > the display can be '0x%x' instead of decimal.
> 
> The values are little endian, just like the xfs metadata csum.

Oh, right, I forgot that :)

> Do you remember how to dynamically switch between different
> interpretations of a field in xfs_db code?

The stupid way is to declare both FLDT types and counting functions
that return nonzero if that checksum type is enabled, and 0 otherwise:

static int
rtcrc32c_count(
       void                    *obj,
       int                     startoff)
{
	if (mp->m_sb.sb_rtcsum_type != XFS_CSUM_TYPE_CRC32C)
		return 0;
	return xfs_rtcsum_payload_size(mp) >> mp->m_rtcsum_shift;
}

static int
rtcrc64_count(
       void                    *obj,
       int                     startoff)
{
	if (mp->m_sb.sb_rtcsum_type != XFS_CSUM_TYPE_CRC64)
		return 0;
	return xfs_rtcsum_payload_size(mp) >> mp->m_rtcsum_shift;
}


       { "crc", FLDT_CRC, OI(bitize(sizeof(struct xfs_rtbuf_blkinfo))),
	rtcrc32c_count, FLD_ARRAY | FLD_COUNT, TYP_DATA },
       { "crc64", FLDT_CRC64, OI(bitize(sizeof(struct xfs_rtbuf_blkinfo))),
	rtcrc64_count, FLD_ARRAY | FLD_COUNT, TYP_DATA },

FLDT_CRC already exists, so I guess you just have to copy-pasta
FLDT_CRC64 into field.c:

	{ FLDT_CRC64, "crc64", fp_crc, "%#x (%s)", SI(bitsz(uint64_t)),
	  0, NULL, NULL },

Though the iocur_crc_valid() call in fp_crc might cause problems here.

--D