xfs: treat CoW fork operations as delalloc for quota accounting

Source kernel commit: 4b4c1326fd7c7210d23d9dd3bfc51f2b6477bb9e

Since the CoW fork only exists in memory, it is incorrect to update the
on-disk quota block counts when we modify the CoW fork.  Unlike the data
fork, even real extents in the CoW fork are only delalloc-style
reservations (on-disk they're owned by the refcountbt) so they must not
be tracked in the on disk quota info.  Ensure the i_delayed_blks
accounting reflects this too.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>

diff --git a/libxfs/xfs_bmap.c b/libxfs/xfs_bmap.c
index 87b9b12a6c2722ccc50a8448b9715564ba3c414d..15a0f8f0c40c4b6f3a0e7e3fb6c57d8853df5e6b 100644 (file)
--- a/libxfs/xfs_bmap.c
+++ b/libxfs/xfs_bmap.c
@@ -3334,8 +3334,35 @@ xfs_bmap_btalloc_accounting(
        struct xfs_bmalloca     *ap,
        struct xfs_alloc_arg    *args)
 {
-       if (!(ap->flags & XFS_BMAPI_COWFORK))
-               ap->ip->i_d.di_nblocks += args->len;
+       if (ap->flags & XFS_BMAPI_COWFORK) {
+               /*
+                * COW fork blocks are in-core only and thus are treated as
+                * in-core quota reservation (like delalloc blocks) even when
+                * converted to real blocks. The quota reservation is not
+                * accounted to disk until blocks are remapped to the data
+                * fork. So if these blocks were previously delalloc, we
+                * already have quota reservation and there's nothing to do
+                * yet.
+                */
+               if (ap->wasdel)
+                       return;
+
+               /*
+                * Otherwise, we've allocated blocks in a hole. The transaction
+                * has acquired in-core quota reservation for this extent.
+                * Rather than account these as real blocks, however, we reduce
+                * the transaction quota reservation based on the allocation.
+                * This essentially transfers the transaction quota reservation
+                * to that of a delalloc extent.
+                */
+               ap->ip->i_delayed_blks += args->len;
+               xfs_trans_mod_dquot_byino(ap->tp, ap->ip, XFS_TRANS_DQ_RES_BLKS,
+                               -(long)args->len);
+               return;
+       }
+
+       /* data/attr fork only */
+       ap->ip->i_d.di_nblocks += args->len;
        xfs_trans_log_inode(ap->tp, ap->ip, XFS_ILOG_CORE);
        if (ap->wasdel)
                ap->ip->i_delayed_blks -= args->len;
@@ -4811,6 +4838,7 @@ xfs_bmap_del_extent_cow(
                xfs_iext_insert(ip, icur, &new, state);
                break;
        }
+       ip->i_delayed_blks -= del->br_blockcount;
 }
 
 /*