[PATCH v4 38/48] xfs: dynamically allocate the xfs-inodegc shrinker

[Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>]

In preparation for implementing lockless slab shrink, use new APIs to
dynamically allocate the xfs-inodegc 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_mount.

Signed-off-by: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
Reviewed-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
---
 fs/xfs/xfs_icache.c | 26 +++++++++++++++-----------
 fs/xfs/xfs_mount.c  |  4 ++--
 fs/xfs/xfs_mount.h  |  2 +-
 3 files changed, 18 insertions(+), 14 deletions(-)

diff --git a/fs/xfs/xfs_icache.c b/fs/xfs/xfs_icache.c
index 453890942d9f..751c380afd5a 100644
--- a/fs/xfs/xfs_icache.c
+++ b/fs/xfs/xfs_icache.c
@@ -2225,8 +2225,7 @@ xfs_inodegc_shrinker_count(
        struct shrinker         *shrink,
        struct shrink_control   *sc)
 {
-       struct xfs_mount        *mp = container_of(shrink, struct xfs_mount,
-                                                  m_inodegc_shrinker);
+       struct xfs_mount        *mp = shrink->private_data;
        struct xfs_inodegc      *gc;
        int                     cpu;
 
@@ -2247,8 +2246,7 @@ xfs_inodegc_shrinker_scan(
        struct shrinker         *shrink,
        struct shrink_control   *sc)
 {
-       struct xfs_mount        *mp = container_of(shrink, struct xfs_mount,
-                                                  m_inodegc_shrinker);
+       struct xfs_mount        *mp = shrink->private_data;
        struct xfs_inodegc      *gc;
        int                     cpu;
        bool                    no_items = true;
@@ -2284,13 +2282,19 @@ int
 xfs_inodegc_register_shrinker(
        struct xfs_mount        *mp)
 {
-       struct shrinker         *shrink = &mp->m_inodegc_shrinker;
+       mp->m_inodegc_shrinker = shrinker_alloc(SHRINKER_NONSLAB,
+                                               "xfs-inodegc:%s",
+                                               mp->m_super->s_id);
+       if (!mp->m_inodegc_shrinker)
+               return -ENOMEM;
+
+       mp->m_inodegc_shrinker->count_objects = xfs_inodegc_shrinker_count;
+       mp->m_inodegc_shrinker->scan_objects = xfs_inodegc_shrinker_scan;
+       mp->m_inodegc_shrinker->seeks = 0;
+       mp->m_inodegc_shrinker->batch = XFS_INODEGC_SHRINKER_BATCH;
+       mp->m_inodegc_shrinker->private_data = mp;
 
-       shrink->count_objects = xfs_inodegc_shrinker_count;
-       shrink->scan_objects = xfs_inodegc_shrinker_scan;
-       shrink->seeks = 0;
-       shrink->flags = SHRINKER_NONSLAB;
-       shrink->batch = XFS_INODEGC_SHRINKER_BATCH;
+       shrinker_register(mp->m_inodegc_shrinker);
 
-       return register_shrinker(shrink, "xfs-inodegc:%s", mp->m_super->s_id);
+       return 0;
 }
diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index fb87ffb48f7f..640d09891a4e 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -1018,7 +1018,7 @@ xfs_mountfs(
  out_log_dealloc:
        xfs_log_mount_cancel(mp);
  out_inodegc_shrinker:
-       unregister_shrinker(&mp->m_inodegc_shrinker);
+       shrinker_free(mp->m_inodegc_shrinker);
  out_fail_wait:
        if (mp->m_logdev_targp && mp->m_logdev_targp != mp->m_ddev_targp)
                xfs_buftarg_drain(mp->m_logdev_targp);
@@ -1100,7 +1100,7 @@ xfs_unmountfs(
 #if defined(DEBUG)
        xfs_errortag_clearall(mp);
 #endif
-       unregister_shrinker(&mp->m_inodegc_shrinker);
+       shrinker_free(mp->m_inodegc_shrinker);
        xfs_free_perag(mp);
 
        xfs_errortag_del(mp);
diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
index e2866e7fa60c..562c294ca08e 100644
--- a/fs/xfs/xfs_mount.h
+++ b/fs/xfs/xfs_mount.h
@@ -217,7 +217,7 @@ typedef struct xfs_mount {
        atomic_t                m_agirotor;     /* last ag dir inode alloced */
 
        /* Memory shrinker to throttle and reprioritize inodegc */
-       struct shrinker         m_inodegc_shrinker;
+       struct shrinker         *m_inodegc_shrinker;
        /*
         * Workqueue item so that we can coalesce multiple inode flush attempts
         * into a single flush.
-- 
2.30.2