Re: [PATCH V7 17/17] xfs: Define max extent length based on on-disk format definition

Dave Chinner
2022-03-04T08:15:53Z

On Tue, Mar 01, 2022 at 04:09:38PM +0530, Chandan Babu R wrote:
> The maximum extent length depends on maximum block count that can be stored in
> a BMBT record. Hence this commit defines MAXEXTLEN based on
> BMBT_BLOCKCOUNT_BITLEN.
>
> While at it, the commit also renames MAXEXTLEN to XFS_MAX_BMBT_EXTLEN.
>
> Suggested-by: Darrick J. Wong <djwong@kernel.org>
> Reviewed-by: Darrick J. Wong <djwong@kernel.org>
> Signed-off-by: Chandan Babu R <chandan.babu@oracle.com>

Looks fine, but this should be up near the top of the series where
all the extent count definitions are being changed. Also, minor
formatting nit below.

Reviewed-by: Dave Chinner <dchinner@redhat.com>

> @@ -299,7 +299,8 @@ xfs_calc_write_reservation(
> * the agf for each of the ags: 2 * sector size
> * the agfl for each of the ags: 2 * sector size
> * the super block to reflect the freed blocks: sector size
> - * the realtime bitmap: 2 exts * ((MAXEXTLEN / rtextsize) / NBBY) bytes
> + * the realtime bitmap: 2 exts * ((XFS_BMBT_MAX_EXTLEN / rtextsize) / NBBY)
> + * bytes

Break the line at the ":"

* the realtime bitmap:
* 2 exts * ((XFS_BMBT_MAX_EXTLEN / rtextsize) / NBBY) bytes

Which makes it consistent with the rest of the comment:

> * the realtime summary: 2 exts * 1 block
> * worst case split in allocation btrees per extent assuming 2 extents:
> * 2 exts * 2 trees * (2 * max depth - 1) * block size

Cheers,

Dave.
--
Dave Chinner
david@fromorbit.com