Re: [PATCH 5/9] xfs: only reserve quota blocks if we're mapping into a hole

Brian Foster
2020-06-25T12:28:12Z

On Wed, Jun 24, 2020 at 06:18:12PM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@oracle.com>
>
> When logging quota block count updates during a reflink operation, we
> only log the /delta/ of the block count changes to the dquot. Since we
> now know ahead of time the extent type of both dmap and smap (and that
> they have the same length), we know that we only need to reserve quota
> blocks for dmap's blockcount if we're mapping it into a hole.
>
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> ---

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

> fs/xfs/xfs_reflink.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
>
> diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
> index 9cc1c340d0ec..72de7179399d 100644
> --- a/fs/xfs/xfs_reflink.c
> +++ b/fs/xfs/xfs_reflink.c
> @@ -1051,7 +1051,9 @@ xfs_reflink_remap_extent(
> *
> * If we are mapping a written extent into the file, we need to have
> * enough quota block count reservation to handle the blocks in that
> - * extent.
> + * extent. We log only the delta to the quota block counts, so if the
> + * extent we're unmapping also has blocks allocated to it, we don't
> + * need a quota reservation for the extent itself.
> *
> * Note that if we're replacing a delalloc reservation with a written
> * extent, we have to take the full quota reservation because removing
> @@ -1063,7 +1065,7 @@ xfs_reflink_remap_extent(
> qres = qdelta = 0;
> if (smap_mapped || dmap_written)
> qres = XFS_EXTENTADD_SPACE_RES(mp, XFS_DATA_FORK);
> - if (dmap_written)
> + if (!smap_mapped && dmap_written)
> qres += dmap->br_blockcount;
> if (qres > 0) {
> error = xfs_trans_reserve_quota_nblks(tp, ip, qres, 0,
>