[PATCH v4 39/48] xfs: dynamically allocate the xfs-qm shrinker

[Qi Zheng via Linux-erofs]

In preparation for implementing lockless slab shrink, use new APIs to
dynamically allocate the xfs-qm shrinker, so that it can be freed
asynchronously using kfree_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.a...@bytedance.com>
Reviewed-by: Muchun Song <songmuc...@bytedance.com>
---
 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