[PATCH] xfs: don't leak perag metadata reservation on finobt block free

[Brian Foster <bfoster@redhat.com>]

We started using the perag metadata reservation for free inode btree
blocks in commit 76d771b4cbe33 ("xfs: use per-AG reservations for
the finobt"). While this change consumes metadata res. for finobt
block allocations, we still don't replenish the res. pool when
finobt blocks are freed. This leads to leaking reservation as finobt
blocks are allocated and freed over time, which in turn can lead to
overruse of blocks that should be protected by the reservation.

Update the finobt free block path to specify the metadata
reservation type as done in the allocation path.

Signed-off-by: Brian Foster <bfoster@redhat.com>
---
 fs/xfs/libxfs/xfs_ialloc_btree.c | 25 +++++++++++++++++++++----
 1 file changed, 21 insertions(+), 4 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_ialloc_btree.c b/fs/xfs/libxfs/xfs_ialloc_btree.c
index 47f44d624cb1..18fe6b3a7802 100644
--- a/fs/xfs/libxfs/xfs_ialloc_btree.c
+++ b/fs/xfs/libxfs/xfs_ialloc_btree.c
@@ -146,16 +146,33 @@ xfs_finobt_alloc_block(
 }
 
 STATIC int
-xfs_inobt_free_block(
+__xfs_inobt_free_block(
 	struct xfs_btree_cur	*cur,
-	struct xfs_buf		*bp)
+	struct xfs_buf		*bp,
+	enum xfs_ag_resv_type	resv)
 {
 	struct xfs_owner_info	oinfo;
 
 	xfs_rmap_ag_owner(&oinfo, XFS_RMAP_OWN_INOBT);
 	return xfs_free_extent(cur->bc_tp,
 			XFS_DADDR_TO_FSB(cur->bc_mp, XFS_BUF_ADDR(bp)), 1,
-			&oinfo, XFS_AG_RESV_NONE);
+			&oinfo, resv);
+}
+
+STATIC int
+xfs_inobt_free_block(
+	struct xfs_btree_cur	*cur,
+	struct xfs_buf		*bp)
+{
+	return __xfs_inobt_free_block(cur, bp, XFS_AG_RESV_NONE);
+}
+
+STATIC int
+xfs_finobt_free_block(
+	struct xfs_btree_cur	*cur,
+	struct xfs_buf		*bp)
+{
+	return __xfs_inobt_free_block(cur, bp, XFS_AG_RESV_METADATA);
 }
 
 STATIC int
@@ -380,7 +397,7 @@ static const struct xfs_btree_ops xfs_finobt_ops = {
 	.dup_cursor		= xfs_inobt_dup_cursor,
 	.set_root		= xfs_finobt_set_root,
 	.alloc_block		= xfs_finobt_alloc_block,
-	.free_block		= xfs_inobt_free_block,
+	.free_block		= xfs_finobt_free_block,
 	.get_minrecs		= xfs_inobt_get_minrecs,
 	.get_maxrecs		= xfs_inobt_get_maxrecs,
 	.init_key_from_rec	= xfs_inobt_init_key_from_rec,
-- 
2.13.6