[PATCH v4 48/48] mm: shrinker: convert shrinker_rwsem to mutex

[Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>]

Now there are no readers of shrinker_rwsem, so we can simply replace it
with mutex lock.

Signed-off-by: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
---
 drivers/md/dm-cache-metadata.c |  2 +-
 fs/super.c                     |  2 +-
 mm/shrinker.c                  | 28 ++++++++++++++--------------
 mm/shrinker_debug.c            | 14 +++++++-------
 4 files changed, 23 insertions(+), 23 deletions(-)

diff --git a/drivers/md/dm-cache-metadata.c b/drivers/md/dm-cache-metadata.c
index acffed750e3e..9e0c69958587 100644
--- a/drivers/md/dm-cache-metadata.c
+++ b/drivers/md/dm-cache-metadata.c
@@ -1828,7 +1828,7 @@ int dm_cache_metadata_abort(struct dm_cache_metadata *cmd)
         * Replacement block manager (new_bm) is created and old_bm destroyed 
outside of
         * cmd root_lock to avoid ABBA deadlock that would result (due to 
life-cycle of
         * shrinker associated with the block manager's bufio client vs cmd 
root_lock).
-        * - must take shrinker_rwsem without holding cmd->root_lock
+        * - must take shrinker_mutex without holding cmd->root_lock
         */
        new_bm = dm_block_manager_create(cmd->bdev, 
DM_CACHE_METADATA_BLOCK_SIZE << SECTOR_SHIFT,
                                         CACHE_MAX_CONCURRENT_LOCKS);
diff --git a/fs/super.c b/fs/super.c
index a28193045345..60c2d290c754 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -54,7 +54,7 @@ static char *sb_writers_name[SB_FREEZE_LEVELS] = {
  * One thing we have to be careful of with a per-sb shrinker is that we don't
  * drop the last active reference to the superblock from within the shrinker.
  * If that happens we could trigger unregistering the shrinker from within the
- * shrinker path and that leads to deadlock on the shrinker_rwsem. Hence we
+ * shrinker path and that leads to deadlock on the shrinker_mutex. Hence we
  * take a passive reference to the superblock to avoid this from occurring.
  */
 static unsigned long super_cache_scan(struct shrinker *shrink,
diff --git a/mm/shrinker.c b/mm/shrinker.c
index a12dede5d21f..3d44a335ef3c 100644
--- a/mm/shrinker.c
+++ b/mm/shrinker.c
@@ -8,7 +8,7 @@
 #include "internal.h"
 
 LIST_HEAD(shrinker_list);
-DECLARE_RWSEM(shrinker_rwsem);
+DEFINE_MUTEX(shrinker_mutex);
 
 #ifdef CONFIG_MEMCG
 static int shrinker_nr_max;
@@ -80,7 +80,7 @@ int alloc_shrinker_info(struct mem_cgroup *memcg)
        int nid, ret = 0;
        int array_size = 0;
 
-       down_write(&shrinker_rwsem);
+       mutex_lock(&shrinker_mutex);
        array_size = shrinker_unit_size(shrinker_nr_max);
        for_each_node(nid) {
                info = kvzalloc_node(sizeof(*info) + array_size, GFP_KERNEL, 
nid);
@@ -91,7 +91,7 @@ int alloc_shrinker_info(struct mem_cgroup *memcg)
                        goto err;
                rcu_assign_pointer(memcg->nodeinfo[nid]->shrinker_info, info);
        }
-       up_write(&shrinker_rwsem);
+       mutex_unlock(&shrinker_mutex);
 
        return ret;
 
@@ -104,7 +104,7 @@ static struct shrinker_info *shrinker_info_protected(struct 
mem_cgroup *memcg,
                                                     int nid)
 {
        return rcu_dereference_protected(memcg->nodeinfo[nid]->shrinker_info,
-                                        lockdep_is_held(&shrinker_rwsem));
+                                        lockdep_is_held(&shrinker_mutex));
 }
 
 static struct shrinker_info *shrinker_info_rcu(struct mem_cgroup *memcg,
@@ -161,7 +161,7 @@ static int expand_shrinker_info(int new_id)
        if (!root_mem_cgroup)
                goto out;
 
-       lockdep_assert_held(&shrinker_rwsem);
+       lockdep_assert_held(&shrinker_mutex);
 
        new_size = shrinker_unit_size(new_nr_max);
        old_size = shrinker_unit_size(shrinker_nr_max);
@@ -224,7 +224,7 @@ static int shrinker_memcg_alloc(struct shrinker *shrinker)
        if (mem_cgroup_disabled())
                return -ENOSYS;
 
-       down_write(&shrinker_rwsem);
+       mutex_lock(&shrinker_mutex);
        id = idr_alloc(&shrinker_idr, shrinker, 0, 0, GFP_KERNEL);
        if (id < 0)
                goto unlock;
@@ -238,7 +238,7 @@ static int shrinker_memcg_alloc(struct shrinker *shrinker)
        shrinker->id = id;
        ret = 0;
 unlock:
-       up_write(&shrinker_rwsem);
+       mutex_unlock(&shrinker_mutex);
        return ret;
 }
 
@@ -248,7 +248,7 @@ static void shrinker_memcg_remove(struct shrinker *shrinker)
 
        BUG_ON(id < 0);
 
-       lockdep_assert_held(&shrinker_rwsem);
+       lockdep_assert_held(&shrinker_mutex);
 
        idr_remove(&shrinker_idr, id);
 }
@@ -299,7 +299,7 @@ void reparent_shrinker_deferred(struct mem_cgroup *memcg)
                parent = root_mem_cgroup;
 
        /* Prevent from concurrent shrinker_info expand */
-       down_write(&shrinker_rwsem);
+       mutex_lock(&shrinker_mutex);
        for_each_node(nid) {
                child_info = shrinker_info_protected(memcg, nid);
                parent_info = shrinker_info_protected(parent, nid);
@@ -312,7 +312,7 @@ void reparent_shrinker_deferred(struct mem_cgroup *memcg)
                        }
                }
        }
-       up_write(&shrinker_rwsem);
+       mutex_unlock(&shrinker_mutex);
 }
 #else
 static int shrinker_memcg_alloc(struct shrinker *shrinker)
@@ -708,11 +708,11 @@ void shrinker_register(struct shrinker *shrinker)
                return;
        }
 
-       down_write(&shrinker_rwsem);
+       mutex_lock(&shrinker_mutex);
        list_add_tail_rcu(&shrinker->list, &shrinker_list);
        shrinker->flags |= SHRINKER_REGISTERED;
        shrinker_debugfs_add(shrinker);
-       up_write(&shrinker_rwsem);
+       mutex_unlock(&shrinker_mutex);
 
        init_completion(&shrinker->done);
        /*
@@ -745,7 +745,7 @@ void shrinker_free(struct shrinker *shrinker)
                wait_for_completion(&shrinker->done);
        }
 
-       down_write(&shrinker_rwsem);
+       mutex_lock(&shrinker_mutex);
        if (shrinker->flags & SHRINKER_REGISTERED) {
                /*
                 * Lookups on the shrinker are over and will fail in the future,
@@ -760,7 +760,7 @@ void shrinker_free(struct shrinker *shrinker)
 
        if (shrinker->flags & SHRINKER_MEMCG_AWARE)
                shrinker_memcg_remove(shrinker);
-       up_write(&shrinker_rwsem);
+       mutex_unlock(&shrinker_mutex);
 
        if (debugfs_entry)
                shrinker_debugfs_remove(debugfs_entry, debugfs_id);
diff --git a/mm/shrinker_debug.c b/mm/shrinker_debug.c
index aa2027075ed9..b698ca9e309e 100644
--- a/mm/shrinker_debug.c
+++ b/mm/shrinker_debug.c
@@ -7,7 +7,7 @@
 #include <linux/memcontrol.h>
 
 /* defined in vmscan.c */
-extern struct rw_semaphore shrinker_rwsem;
+extern struct mutex shrinker_mutex;
 extern struct list_head shrinker_list;
 
 static DEFINE_IDA(shrinker_debugfs_ida);
@@ -163,7 +163,7 @@ int shrinker_debugfs_add(struct shrinker *shrinker)
        char buf[128];
        int id;
 
-       lockdep_assert_held(&shrinker_rwsem);
+       lockdep_assert_held(&shrinker_mutex);
 
        /* debugfs isn't initialized yet, add debugfs entries later. */
        if (!shrinker_debugfs_root)
@@ -220,7 +220,7 @@ int shrinker_debugfs_rename(struct shrinker *shrinker, 
const char *fmt, ...)
        if (!new)
                return -ENOMEM;
 
-       down_write(&shrinker_rwsem);
+       mutex_lock(&shrinker_mutex);
 
        old = shrinker->name;
        shrinker->name = new;
@@ -238,7 +238,7 @@ int shrinker_debugfs_rename(struct shrinker *shrinker, 
const char *fmt, ...)
                        shrinker->debugfs_entry = entry;
        }
 
-       up_write(&shrinker_rwsem);
+       mutex_unlock(&shrinker_mutex);
 
        kfree_const(old);
 
@@ -251,7 +251,7 @@ struct dentry *shrinker_debugfs_detach(struct shrinker 
*shrinker,
 {
        struct dentry *entry = shrinker->debugfs_entry;
 
-       lockdep_assert_held(&shrinker_rwsem);
+       lockdep_assert_held(&shrinker_mutex);
 
        shrinker_debugfs_name_free(shrinker);
 
@@ -279,14 +279,14 @@ static int __init shrinker_debugfs_init(void)
        shrinker_debugfs_root = dentry;
 
        /* Create debugfs entries for shrinkers registered at boot */
-       down_write(&shrinker_rwsem);
+       mutex_lock(&shrinker_mutex);
        list_for_each_entry(shrinker, &shrinker_list, list)
                if (!shrinker->debugfs_entry) {
                        ret = shrinker_debugfs_add(shrinker);
                        if (ret)
                                break;
                }
-       up_write(&shrinker_rwsem);
+       mutex_unlock(&shrinker_mutex);
 
        return ret;
 }
-- 
2.30.2