Re: [PATCH 29/42] xfs: convert trim to use for_each_perag_range

Darrick J. Wong
2023-02-01T23:16:56Z

On Thu, Jan 19, 2023 at 09:44:52AM +1100, Dave Chinner wrote:
> From: Dave Chinner <dchinner@redhat.com>
>
> To convert it to using active perag references and hence make it
> shrink safe.
>
> Signed-off-by: Dave Chinner <dchinner@redhat.com>
> ---
> fs/xfs/xfs_discard.c | 50 ++++++++++++++++++++------------------------
> 1 file changed, 23 insertions(+), 27 deletions(-)
>
> diff --git a/fs/xfs/xfs_discard.c b/fs/xfs/xfs_discard.c
> index bfc829c07f03..afc4c78b9eed 100644
> --- a/fs/xfs/xfs_discard.c
> +++ b/fs/xfs/xfs_discard.c
> @@ -21,23 +21,20 @@
>
> STATIC int
> xfs_trim_extents(
> - struct xfs_mount *mp,
> - xfs_agnumber_t agno,
> + struct xfs_perag *pag,
> xfs_daddr_t start,
> xfs_daddr_t end,
> xfs_daddr_t minlen,
> uint64_t *blocks_trimmed)
> {
> + struct xfs_mount *mp = pag->pag_mount;
> struct block_device *bdev = mp->m_ddev_targp->bt_bdev;
> struct xfs_btree_cur *cur;
> struct xfs_buf *agbp;
> struct xfs_agf *agf;
> - struct xfs_perag *pag;
> int error;
> int i;
>
> - pag = xfs_perag_get(mp, agno);
> -
> /*
> * Force out the log. This means any transactions that might have freed

This is a tangent, but one thing I've wondered is if it's really
necessary to force the log for *every* AG that we want to trim? Even if
we've just come from trimming the previous AG?

Looks good otherwise,
Reviewed-by: Darrick J. Wong <djwong@kernel.org>

--D

> * space before we take the AGF buffer lock are now on disk, and the
> @@ -47,7 +44,7 @@ xfs_trim_extents(
>
> error = xfs_alloc_read_agf(pag, NULL, 0, &agbp);
> if (error)
> - goto out_put_perag;
> + return error;
> agf = agbp->b_addr;
>
> cur = xfs_allocbt_init_cursor(mp, NULL, agbp, pag, XFS_BTNUM_CNT);
> @@ -71,10 +68,10 @@ xfs_trim_extents(
>
> error = xfs_alloc_get_rec(cur, &fbno, &flen, &i);
> if (error)
> - goto out_del_cursor;
> + break;
> if (XFS_IS_CORRUPT(mp, i != 1)) {
> error = -EFSCORRUPTED;
> - goto out_del_cursor;
> + break;
> }
> ASSERT(flen <= be32_to_cpu(agf->agf_longest));
>
> @@ -83,15 +80,15 @@ xfs_trim_extents(
> * the format the range/len variables are supplied in by
> * userspace.
> */
> - dbno = XFS_AGB_TO_DADDR(mp, agno, fbno);
> + dbno = XFS_AGB_TO_DADDR(mp, pag->pag_agno, fbno);
> dlen = XFS_FSB_TO_BB(mp, flen);
>
> /*
> * Too small? Give up.
> */
> if (dlen < minlen) {
> - trace_xfs_discard_toosmall(mp, agno, fbno, flen);
> - goto out_del_cursor;
> + trace_xfs_discard_toosmall(mp, pag->pag_agno, fbno, flen);
> + break;
> }
>
> /*
> @@ -100,7 +97,7 @@ xfs_trim_extents(
> * down partially overlapping ranges for now.
> */
> if (dbno + dlen < start || dbno > end) {
> - trace_xfs_discard_exclude(mp, agno, fbno, flen);
> + trace_xfs_discard_exclude(mp, pag->pag_agno, fbno, flen);
> goto next_extent;
> }
>
> @@ -109,32 +106,30 @@ xfs_trim_extents(
> * discard and try again the next time.
> */
> if (xfs_extent_busy_search(mp, pag, fbno, flen)) {
> - trace_xfs_discard_busy(mp, agno, fbno, flen);
> + trace_xfs_discard_busy(mp, pag->pag_agno, fbno, flen);
> goto next_extent;
> }
>
> - trace_xfs_discard_extent(mp, agno, fbno, flen);
> + trace_xfs_discard_extent(mp, pag->pag_agno, fbno, flen);
> error = blkdev_issue_discard(bdev, dbno, dlen, GFP_NOFS);
> if (error)
> - goto out_del_cursor;
> + break;
> *blocks_trimmed += flen;
>
> next_extent:
> error = xfs_btree_decrement(cur, 0, &i);
> if (error)
> - goto out_del_cursor;
> + break;
>
> if (fatal_signal_pending(current)) {
> error = -ERESTARTSYS;
> - goto out_del_cursor;
> + break;
> }
> }
>
> out_del_cursor:
> xfs_btree_del_cursor(cur, error);
> xfs_buf_relse(agbp);
> -out_put_perag:
> - xfs_perag_put(pag);
> return error;
> }
>
> @@ -152,11 +147,12 @@ xfs_ioc_trim(
> struct xfs_mount *mp,
> struct fstrim_range __user *urange)
> {
> + struct xfs_perag *pag;
> unsigned int granularity =
> bdev_discard_granularity(mp->m_ddev_targp->bt_bdev);
> struct fstrim_range range;
> xfs_daddr_t start, end, minlen;
> - xfs_agnumber_t start_agno, end_agno, agno;
> + xfs_agnumber_t agno;
> uint64_t blocks_trimmed = 0;
> int error, last_error = 0;
>
> @@ -193,18 +189,18 @@ xfs_ioc_trim(
> end = start + BTOBBT(range.len) - 1;
>
> if (end > XFS_FSB_TO_BB(mp, mp->m_sb.sb_dblocks) - 1)
> - end = XFS_FSB_TO_BB(mp, mp->m_sb.sb_dblocks)- 1;
> -
> - start_agno = xfs_daddr_to_agno(mp, start);
> - end_agno = xfs_daddr_to_agno(mp, end);
> + end = XFS_FSB_TO_BB(mp, mp->m_sb.sb_dblocks) - 1;
>
> - for (agno = start_agno; agno <= end_agno; agno++) {
> - error = xfs_trim_extents(mp, agno, start, end, minlen,
> + agno = xfs_daddr_to_agno(mp, start);
> + for_each_perag_range(mp, agno, xfs_daddr_to_agno(mp, end), pag) {
> + error = xfs_trim_extents(pag, start, end, minlen,
> &blocks_trimmed);
> if (error) {
> last_error = error;
> - if (error == -ERESTARTSYS)
> + if (error == -ERESTARTSYS) {
> + xfs_perag_rele(pag);
> break;
> + }
> }
> }
>
> --
> 2.39.0
>