Re: [PATCH 09/13] xfs: refactor reflink functions to use xfs_trans_alloc_inode

Brian Foster
2021-01-28T18:28:00Z

On Wed, Jan 27, 2021 at 10:01:55PM -0800, Darrick J. Wong wrote:
> From: Darrick J. Wong <djwong@kernel.org>
>
> The two remaining callers of xfs_trans_reserve_quota_nblks are in the
> reflink code. These conversions aren't as uniform as the previous
> conversions, so call that out in a separate patch.
>
> Signed-off-by: Darrick J. Wong <djwong@kernel.org>
> ---

Modulo Christoph's feedback on the locking:

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

> fs/xfs/xfs_reflink.c | 58 +++++++++++++++++++++-----------------------------
> 1 file changed, 24 insertions(+), 34 deletions(-)
>
>
> diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
> index 0778b5810c26..ded86cc4764c 100644
> --- a/fs/xfs/xfs_reflink.c
> +++ b/fs/xfs/xfs_reflink.c
> @@ -376,16 +376,15 @@ xfs_reflink_allocate_cow(
> resblks = XFS_DIOSTRAT_SPACE_RES(mp, resaligned);
>
> xfs_iunlock(ip, *lockmode);
> - error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, resblks, 0, 0, &tp);
> - *lockmode = XFS_ILOCK_EXCL;
> - xfs_ilock(ip, *lockmode);
>
> - if (error)
> + error = xfs_trans_alloc_inode(ip, &M_RES(mp)->tr_write, resblks, 0,
> + false, &tp);
> + if (error) {
> + /* This function must return with ILOCK_EXCL held. */
> + *lockmode = XFS_ILOCK_EXCL;
> + xfs_ilock(ip, *lockmode);
> return error;
> -
> - error = xfs_qm_dqattach_locked(ip, false);
> - if (error)
> - goto out_trans_cancel;
> + }
>
> /*
> * Check for an overlapping extent again now that we dropped the ilock.
> @@ -398,12 +397,6 @@ xfs_reflink_allocate_cow(
> goto convert;
> }
>
> - error = xfs_trans_reserve_quota_nblks(tp, ip, resblks, 0, false);
> - if (error)
> - goto out_trans_cancel;
> -
> - xfs_trans_ijoin(tp, ip, 0);
> -
> /* Allocate the entire reservation as unwritten blocks. */
> nimaps = 1;
> error = xfs_bmapi_write(tp, ip, imap->br_startoff, imap->br_blockcount,
> @@ -997,7 +990,7 @@ xfs_reflink_remap_extent(
> struct xfs_mount *mp = ip->i_mount;
> struct xfs_trans *tp;
> xfs_off_t newlen;
> - int64_t qres, qdelta;
> + int64_t qdelta = 0;
> unsigned int resblks;
> bool smap_real;
> bool dmap_written = xfs_bmap_is_written_extent(dmap);
> @@ -1005,15 +998,22 @@ xfs_reflink_remap_extent(
> int nimaps;
> int error;
>
> - /* Start a rolling transaction to switch the mappings */
> + /*
> + * Start a rolling transaction to switch the mappings.
> + *
> + * Adding a written extent to the extent map can cause a bmbt split,
> + * and removing a mapped extent from the extent can cause a bmbt split.
> + * The two operations cannot both cause a split since they operate on
> + * the same index in the bmap btree, so we only need a reservation for
> + * one bmbt split if either thing is happening. However, we haven't
> + * locked the inode yet, so we reserve assuming this is the case.
> + */
> resblks = XFS_EXTENTADD_SPACE_RES(mp, XFS_DATA_FORK);
> - error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, resblks, 0, 0, &tp);
> + error = xfs_trans_alloc_inode(ip, &M_RES(mp)->tr_write, resblks, 0,
> + false, &tp);
> if (error)
> goto out;
>
> - xfs_ilock(ip, XFS_ILOCK_EXCL);
> - xfs_trans_ijoin(tp, ip, 0);
> -
> /*
> * Read what's currently mapped in the destination file into smap.
> * If smap isn't a hole, we will have to remove it before we can add
> @@ -1061,15 +1061,9 @@ xfs_reflink_remap_extent(
> }
>
> /*
> - * Compute quota reservation if we think the quota block counter for
> + * Increase quota reservation if we think the quota block counter for
> * this file could increase.
> *
> - * Adding a written extent to the extent map can cause a bmbt split,
> - * and removing a mapped extent from the extent can cause a bmbt split.
> - * The two operations cannot both cause a split since they operate on
> - * the same index in the bmap btree, so we only need a reservation for
> - * one bmbt split if either thing is happening.
> - *
> * 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. We log only the delta to the quota block counts, so if the
> @@ -1083,13 +1077,9 @@ xfs_reflink_remap_extent(
> * before we started. That should have removed all the delalloc
> * reservations, but we code defensively.
> */
> - qres = qdelta = 0;
> - if (smap_real || dmap_written)
> - qres = XFS_EXTENTADD_SPACE_RES(mp, XFS_DATA_FORK);
> - if (!smap_real && dmap_written)
> - qres += dmap->br_blockcount;
> - if (qres > 0) {
> - error = xfs_trans_reserve_quota_nblks(tp, ip, qres, 0, false);
> + if (!smap_real && dmap_written) {
> + error = xfs_trans_reserve_quota_nblks(tp, ip,
> + dmap->br_blockcount, 0, false);
> if (error)
> goto out_cancel;
> }
>