[PATCH v5 36/45] xfs: dynamically allocate the xfs-qm shrinker

[Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>]

In preparation for implementing lockless slab shrink, use new APIs to
dynamically allocate the xfs-qm shrinker, so that it can be freed
asynchronously via RCU. Then it doesn't need to wait for RCU read-side
critical section when releasing the struct xfs_quotainfo.

Signed-off-by: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
Reviewed-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
CC: Chandan Babu R <chandan.babu@xxxxxxxxxx>
CC: "Darrick J. Wong" <djwong@xxxxxxxxxx>
CC: linux-xfs@xxxxxxxxxxxxxxx
---
 fs/xfs/xfs_qm.c | 28 +++++++++++++++-------------
 fs/xfs/xfs_qm.h |  2 +-
 2 files changed, 16 insertions(+), 14 deletions(-)

diff --git a/fs/xfs/xfs_qm.c b/fs/xfs/xfs_qm.c
index 6abcc34fafd8..15ba23f11271 100644
--- a/fs/xfs/xfs_qm.c
+++ b/fs/xfs/xfs_qm.c
@@ -504,8 +504,7 @@ xfs_qm_shrink_scan(
 	struct shrinker		*shrink,
 	struct shrink_control	*sc)
 {
-	struct xfs_quotainfo	*qi = container_of(shrink,
-					struct xfs_quotainfo, qi_shrinker);
+	struct xfs_quotainfo	*qi = shrink->private_data;
 	struct xfs_qm_isolate	isol;
 	unsigned long		freed;
 	int			error;
@@ -539,8 +538,7 @@ xfs_qm_shrink_count(
 	struct shrinker		*shrink,
 	struct shrink_control	*sc)
 {
-	struct xfs_quotainfo	*qi = container_of(shrink,
-					struct xfs_quotainfo, qi_shrinker);
+	struct xfs_quotainfo	*qi = shrink->private_data;
 
 	return list_lru_shrink_count(&qi->qi_lru, sc);
 }
@@ -680,15 +678,19 @@ xfs_qm_init_quotainfo(
 	if (XFS_IS_PQUOTA_ON(mp))
 		xfs_qm_set_defquota(mp, XFS_DQTYPE_PROJ, qinf);
 
-	qinf->qi_shrinker.count_objects = xfs_qm_shrink_count;
-	qinf->qi_shrinker.scan_objects = xfs_qm_shrink_scan;
-	qinf->qi_shrinker.seeks = DEFAULT_SEEKS;
-	qinf->qi_shrinker.flags = SHRINKER_NUMA_AWARE;
-
-	error = register_shrinker(&qinf->qi_shrinker, "xfs-qm:%s",
-				  mp->m_super->s_id);
-	if (error)
+	qinf->qi_shrinker = shrinker_alloc(SHRINKER_NUMA_AWARE, "xfs-qm:%s",
+					   mp->m_super->s_id);
+	if (!qinf->qi_shrinker) {
+		error = -ENOMEM;
 		goto out_free_inos;
+	}
+
+	qinf->qi_shrinker->count_objects = xfs_qm_shrink_count;
+	qinf->qi_shrinker->scan_objects = xfs_qm_shrink_scan;
+	qinf->qi_shrinker->seeks = DEFAULT_SEEKS;
+	qinf->qi_shrinker->private_data = qinf;
+
+	shrinker_register(qinf->qi_shrinker);
 
 	return 0;
 
@@ -718,7 +720,7 @@ xfs_qm_destroy_quotainfo(
 	qi = mp->m_quotainfo;
 	ASSERT(qi != NULL);
 
-	unregister_shrinker(&qi->qi_shrinker);
+	shrinker_free(qi->qi_shrinker);
 	list_lru_destroy(&qi->qi_lru);
 	xfs_qm_destroy_quotainos(qi);
 	mutex_destroy(&qi->qi_tree_lock);
diff --git a/fs/xfs/xfs_qm.h b/fs/xfs/xfs_qm.h
index 9683f0457d19..d5c9fc4ba591 100644
--- a/fs/xfs/xfs_qm.h
+++ b/fs/xfs/xfs_qm.h
@@ -63,7 +63,7 @@ struct xfs_quotainfo {
 	struct xfs_def_quota	qi_usr_default;
 	struct xfs_def_quota	qi_grp_default;
 	struct xfs_def_quota	qi_prj_default;
-	struct shrinker		qi_shrinker;
+	struct shrinker		*qi_shrinker;
 
 	/* Minimum and maximum quota expiration timestamp values. */
 	time64_t		qi_expiry_min;
-- 
2.30.2