Re: [PATCH 1/3] xfs: refactor agfl length computation function

Brian Foster
2019-12-19T13:17:32Z

On Wed, Dec 18, 2019 at 11:37:28AM -0800, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@oracle.com>
>
> Refactor xfs_alloc_min_freelist to accept a NULL @pag argument, in which
> case it returns the largest possible minimum length. This will be used
> in an upcoming patch to compute the length of the AGFL at mkfs time.
>
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> ---

Reviewed-by: Brian Foster <bfoster@redhat.com>

> fs/xfs/libxfs/xfs_alloc.c | 18 +++++++++++++-----
> 1 file changed, 13 insertions(+), 5 deletions(-)
>
>
> diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c
> index c284e10af491..fc93fd88ec89 100644
> --- a/fs/xfs/libxfs/xfs_alloc.c
> +++ b/fs/xfs/libxfs/xfs_alloc.c
> @@ -2248,24 +2248,32 @@ xfs_alloc_longest_free_extent(
> return pag->pagf_flcount > 0 || pag->pagf_longest > 0;
> }
>
> +/*
> + * Compute the minimum length of the AGFL in the given AG. If @pag is NULL,
> + * return the largest possible minimum length.
> + */
> unsigned int
> xfs_alloc_min_freelist(
> struct xfs_mount *mp,
> struct xfs_perag *pag)
> {
> + /* AG btrees have at least 1 level. */
> + static const uint8_t fake_levels[XFS_BTNUM_AGF] = {1, 1, 1};
> + const uint8_t *levels = pag ? pag->pagf_levels : fake_levels;
> unsigned int min_free;
>
> + ASSERT(mp->m_ag_maxlevels > 0);
> +
> /* space needed by-bno freespace btree */
> - min_free = min_t(unsigned int, pag->pagf_levels[XFS_BTNUM_BNOi] + 1,
> + min_free = min_t(unsigned int, levels[XFS_BTNUM_BNOi] + 1,
> mp->m_ag_maxlevels);
> /* space needed by-size freespace btree */
> - min_free += min_t(unsigned int, pag->pagf_levels[XFS_BTNUM_CNTi] + 1,
> + min_free += min_t(unsigned int, levels[XFS_BTNUM_CNTi] + 1,
> mp->m_ag_maxlevels);
> /* space needed reverse mapping used space btree */
> if (xfs_sb_version_hasrmapbt(&mp->m_sb))
> - min_free += min_t(unsigned int,
> - pag->pagf_levels[XFS_BTNUM_RMAPi] + 1,
> - mp->m_rmap_maxlevels);
> + min_free += min_t(unsigned int, levels[XFS_BTNUM_RMAPi] + 1,
> + mp->m_rmap_maxlevels);
>
> return min_free;
> }
>