[PATCH v5 8/8] mm: shrinkers: convert shrinker_rwsem to mutex

From: Qi Zheng
Date: Mon Mar 13 2023 - 07:31:48 EST

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In reply to: Qi Zheng: "[PATCH v5 7/8] mm: vmscan: remove shrinker_rwsem from synchronize_shrinkers()"
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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>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Acked-by: Kirill Tkhai <tkhai@xxxxx>
---
drivers/md/dm-cache-metadata.c | 2 +-
drivers/md/dm-thin-metadata.c | 2 +-
fs/super.c | 2 +-
mm/shrinker_debug.c | 14 +++++++-------
mm/vmscan.c | 34 +++++++++++++++++-----------------
5 files changed, 27 insertions(+), 27 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/drivers/md/dm-thin-metadata.c b/drivers/md/dm-thin-metadata.c
index fd464fb024c3..9f5cb52c5763 100644
--- a/drivers/md/dm-thin-metadata.c
+++ b/drivers/md/dm-thin-metadata.c
@@ -1887,7 +1887,7 @@ int dm_pool_abort_metadata(struct dm_pool_metadata *pmd)
* Replacement block manager (new_bm) is created and old_bm destroyed outside of
* pmd root_lock to avoid ABBA deadlock that would result (due to life-cycle of
* shrinker associated with the block manager's bufio client vs pmd root_lock).
- * - must take shrinker_rwsem without holding pmd->root_lock
+ * - must take shrinker_mutex without holding pmd->root_lock
*/
new_bm = dm_block_manager_create(pmd->bdev, THIN_METADATA_BLOCK_SIZE << SECTOR_SHIFT,
THIN_MAX_CONCURRENT_LOCKS);
diff --git a/fs/super.c b/fs/super.c
index 84332d5cb817..91a4037b1d95 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_debug.c b/mm/shrinker_debug.c
index 37d54d037495..fdd155fd35ed 100644
--- a/mm/shrinker_debug.c
+++ b/mm/shrinker_debug.c
@@ -8,7 +8,7 @@
#include <linux/srcu.h>

/* defined in vmscan.c */
-extern struct rw_semaphore shrinker_rwsem;
+extern struct mutex shrinker_mutex;
extern struct list_head shrinker_list;
extern struct srcu_struct shrinker_srcu;

@@ -168,7 +168,7 @@ 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)
@@ -211,7 +211,7 @@ 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;
@@ -229,7 +229,7 @@ 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);

@@ -241,7 +241,7 @@ struct dentry *shrinker_debugfs_remove(struct shrinker *shrinker)
{
struct dentry *entry = shrinker->debugfs_entry;

- lockdep_assert_held(&shrinker_rwsem);
+ lockdep_assert_held(&shrinker_mutex);

kfree_const(shrinker->name);
shrinker->name = NULL;
@@ -266,14 +266,14 @@ 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;
}
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 2b22a42d83c4..8faac4310cb5 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -35,7 +35,7 @@
#include <linux/cpuset.h>
#include <linux/compaction.h>
#include <linux/notifier.h>
-#include <linux/rwsem.h>
+#include <linux/mutex.h>
#include <linux/delay.h>
#include <linux/kthread.h>
#include <linux/freezer.h>
@@ -202,7 +202,7 @@ static void set_task_reclaim_state(struct task_struct *task,
}

LIST_HEAD(shrinker_list);
-DECLARE_RWSEM(shrinker_rwsem);
+DEFINE_MUTEX(shrinker_mutex);
DEFINE_SRCU(shrinker_srcu);
static atomic_t shrinker_srcu_generation = ATOMIC_INIT(0);

@@ -225,7 +225,7 @@ static struct shrinker_info *shrinker_info_protected(struct mem_cgroup *memcg,
{
return srcu_dereference_check(memcg->nodeinfo[nid]->shrinker_info,
&shrinker_srcu,
- lockdep_is_held(&shrinker_rwsem));
+ lockdep_is_held(&shrinker_mutex));
}

static struct shrinker_info *shrinker_info_srcu(struct mem_cgroup *memcg,
@@ -304,7 +304,7 @@ int alloc_shrinker_info(struct mem_cgroup *memcg)
int nid, size, ret = 0;
int map_size, defer_size = 0;

- down_write(&shrinker_rwsem);
+ mutex_lock(&shrinker_mutex);
map_size = shrinker_map_size(shrinker_nr_max);
defer_size = shrinker_defer_size(shrinker_nr_max);
size = map_size + defer_size;
@@ -320,7 +320,7 @@ int alloc_shrinker_info(struct mem_cgroup *memcg)
info->map_nr_max = shrinker_nr_max;
rcu_assign_pointer(memcg->nodeinfo[nid]->shrinker_info, info);
}
- up_write(&shrinker_rwsem);
+ mutex_unlock(&shrinker_mutex);

return ret;
}
@@ -336,7 +336,7 @@ static int expand_shrinker_info(int new_id)
if (!root_mem_cgroup)
goto out;

- lockdep_assert_held(&shrinker_rwsem);
+ lockdep_assert_held(&shrinker_mutex);

map_size = shrinker_map_size(new_nr_max);
defer_size = shrinker_defer_size(new_nr_max);
@@ -386,7 +386,7 @@ static int prealloc_memcg_shrinker(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;
@@ -400,7 +400,7 @@ static int prealloc_memcg_shrinker(struct shrinker *shrinker)
shrinker->id = id;
ret = 0;
unlock:
- up_write(&shrinker_rwsem);
+ mutex_unlock(&shrinker_mutex);
return ret;
}

@@ -410,7 +410,7 @@ static void unregister_memcg_shrinker(struct shrinker *shrinker)

BUG_ON(id < 0);

- lockdep_assert_held(&shrinker_rwsem);
+ lockdep_assert_held(&shrinker_mutex);

idr_remove(&shrinker_idr, id);
}
@@ -445,7 +445,7 @@ 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);
@@ -454,7 +454,7 @@ void reparent_shrinker_deferred(struct mem_cgroup *memcg)
atomic_long_add(nr, &parent_info->nr_deferred[i]);
}
}
- up_write(&shrinker_rwsem);
+ mutex_unlock(&shrinker_mutex);
}

static bool cgroup_reclaim(struct scan_control *sc)
@@ -703,9 +703,9 @@ void free_prealloced_shrinker(struct shrinker *shrinker)
shrinker->name = NULL;
#endif
if (shrinker->flags & SHRINKER_MEMCG_AWARE) {
- down_write(&shrinker_rwsem);
+ mutex_lock(&shrinker_mutex);
unregister_memcg_shrinker(shrinker);
- up_write(&shrinker_rwsem);
+ mutex_unlock(&shrinker_mutex);
return;
}

@@ -715,11 +715,11 @@ void free_prealloced_shrinker(struct shrinker *shrinker)

void register_shrinker_prepared(struct shrinker *shrinker)
{
- 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);
}

static int __register_shrinker(struct shrinker *shrinker)
@@ -769,13 +769,13 @@ void unregister_shrinker(struct shrinker *shrinker)
if (!(shrinker->flags & SHRINKER_REGISTERED))
return;

- down_write(&shrinker_rwsem);
+ mutex_lock(&shrinker_mutex);
list_del_rcu(&shrinker->list);
shrinker->flags &= ~SHRINKER_REGISTERED;
if (shrinker->flags & SHRINKER_MEMCG_AWARE)
unregister_memcg_shrinker(shrinker);
debugfs_entry = shrinker_debugfs_remove(shrinker);
- up_write(&shrinker_rwsem);
+ mutex_unlock(&shrinker_mutex);

atomic_inc(&shrinker_srcu_generation);
synchronize_srcu(&shrinker_srcu);
--
2.20.1

Next message: Péter Ujfalusi: "Re: [PATCH 2/6] kbuild: deb-pkg: do not take KERNELRELEASE from the source version"
Previous message: Qi Zheng: "[PATCH v5 7/8] mm: vmscan: remove shrinker_rwsem from synchronize_shrinkers()"
In reply to: Qi Zheng: "[PATCH v5 7/8] mm: vmscan: remove shrinker_rwsem from synchronize_shrinkers()"
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