On Wed, May 22, 2019 at 02:05:38PM -0400, Brian Foster wrote:
> The small allocation helper is implemented in a way that is fairly
> tightly integrated to the existing allocation algorithms. It expects
> a cntbt cursor beyond the end of the tree, attempts to locate the
> last record in the tree and only attempts an AGFL allocation if the
> cntbt is empty.
>
> The upcoming generic algorithm doesn't rely on the cntbt processing
> of this function. It will only call this function when the cntbt
> doesn't have a big enough extent or is empty and thus AGFL
> allocation is the only remaining option. Tweak
> xfs_alloc_ag_vextent_small() to handle a NULL cntbt cursor and skip
> the cntbt logic. This facilitates use by the existing allocation
> code and new code that only requires an AGFL allocation attempt.
>
> Signed-off-by: Brian Foster <bfoster@xxxxxxxxxx>
> Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Looks ok,
Reviewed-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
--D
> ---
> fs/xfs/libxfs/xfs_alloc.c | 11 +++++++++--
> 1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c
> index b345fe771c54..436f8eb0bc4c 100644
> --- a/fs/xfs/libxfs/xfs_alloc.c
> +++ b/fs/xfs/libxfs/xfs_alloc.c
> @@ -713,9 +713,16 @@ xfs_alloc_ag_vextent_small(
> int error = 0;
> xfs_agblock_t fbno = NULLAGBLOCK;
> xfs_extlen_t flen = 0;
> - int i;
> + int i = 0;
>
> - error = xfs_btree_decrement(ccur, 0, &i);
> + /*
> + * If a cntbt cursor is provided, try to allocate the largest record in
> + * the tree. Try the AGFL if the cntbt is empty, otherwise fail the
> + * allocation. Make sure to respect minleft even when pulling from the
> + * freelist.
> + */
> + if (ccur)
> + error = xfs_btree_decrement(ccur, 0, &i);
> if (error)
> goto error;
> if (i) {
> --
> 2.17.2
>
