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Revert "mm: shrinkers: convert shrinker_rwsem to mutex" 

Conflicts: drivers/md/dm-thin-metadata.c - We already have
	d48300120627 ("dm thin metadata: Fix ABBA deadlock by resetting
dm_bufio_client")
	so conflicted code is gone

JIRA: https://issues.redhat.com/browse/RHEL-27741

commit 47a7c01c3efc6581f5dcca40928baeb38e1e40c2
Author: Qi Zheng <zhengqi.arch@bytedance.com>
Date:   Fri Jun 9 08:15:12 2023 +0000

    Revert "mm: shrinkers: convert shrinker_rwsem to mutex"

    Patch series "revert shrinker_srcu related changes".

    This patch (of 7):

    This reverts commit cf2e309ebca7bb0916771839f9b580b06c778530.

    Kernel test robot reports -88.8% regression in stress-ng.ramfs.ops_per_sec
    test case [1], which is caused by commit f95bdb700bc6 ("mm: vmscan: make
    global slab shrink lockless").  The root cause is that SRCU has to be
    careful to not frequently check for SRCU read-side critical section exits.
    Therefore, even if no one is currently in the SRCU read-side critical
    section, synchronize_srcu() cannot return quickly.  That's why
    unregister_shrinker() has become slower.

    After discussion, we will try to use the refcount+RCU method [2] proposed
    by Dave Chinner to continue to re-implement the lockless slab shrink.  So
    revert the shrinker_mutex back to shrinker_rwsem first.

    [1]. https://lore.kernel.org/lkml/202305230837.db2c233f-yujie.liu@intel.com/
    [2]. https://lore.kernel.org/lkml/ZIJhou1d55d4H1s0@dread.disaster.area/

    Link: https://lkml.kernel.org/r/20230609081518.3039120-1-qi.zheng@linux.dev
    Link: https://lkml.kernel.org/r/20230609081518.3039120-2-qi.zheng@linux.dev
    Reported-by: kernel test robot <yujie.liu@intel.com>
    Closes: https://lore.kernel.org/oe-lkp/202305230837.db2c233f-yujie.liu@intel
.com
    Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
    Cc: Dave Chinner <david@fromorbit.com>
    Cc: Kirill Tkhai <tkhai@ya.ru>
    Cc: Muchun Song <muchun.song@linux.dev>
    Cc: Roman Gushchin <roman.gushchin@linux.dev>
    Cc: Vlastimil Babka <vbabka@suse.cz>
    Cc: Yujie Liu <yujie.liu@intel.com>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Signed-off-by: Chris von Recklinghausen <crecklin@redhat.com>
This commit is contained in:
Chris von Recklinghausen 2024-04-12 15:17:09 -04:00
parent 2f0ee0c1c4
commit d91048d120
4 changed files with 26 additions and 26 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
drivers/md/dm-cache-metadata.c
View File

@ -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 * 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 * 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). * shrinker associated with the block manager's bufio client vs cmd root_lock).
* - must take shrinker_mutex without holding cmd->root_lock * - must take shrinker_rwsem without holding cmd->root_lock
*/ */
new_bm = dm_block_manager_create(cmd->bdev, DM_CACHE_METADATA_BLOCK_SIZE << SECTOR_SHIFT, new_bm = dm_block_manager_create(cmd->bdev, DM_CACHE_METADATA_BLOCK_SIZE << SECTOR_SHIFT,
CACHE_MAX_CONCURRENT_LOCKS); CACHE_MAX_CONCURRENT_LOCKS);

2
fs/super.c
View File

@ -178,7 +178,7 @@ static void super_wake(struct super_block *sb, unsigned int flag)
* One thing we have to be careful of with a per-sb shrinker is that we don't * 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. * drop the last active reference to the superblock from within the shrinker.
* If that happens we could trigger unregistering the shrinker from within the * If that happens we could trigger unregistering the shrinker from within the
* shrinker path and that leads to deadlock on the shrinker_mutex. Hence we * shrinker path and that leads to deadlock on the shrinker_rwsem. Hence we
* take a passive reference to the superblock to avoid this from occurring. * take a passive reference to the superblock to avoid this from occurring.
*/ */
static unsigned long super_cache_scan(struct shrinker *shrink, static unsigned long super_cache_scan(struct shrinker *shrink,

14
mm/shrinker_debug.c
View File

@ -8,7 +8,7 @@
#include <linux/srcu.h> #include <linux/srcu.h>
/* defined in vmscan.c */ /* defined in vmscan.c */
extern struct mutex shrinker_mutex; extern struct rw_semaphore shrinker_rwsem;
extern struct list_head shrinker_list; extern struct list_head shrinker_list;
extern struct srcu_struct shrinker_srcu; extern struct srcu_struct shrinker_srcu;
@ -168,7 +168,7 @@ int shrinker_debugfs_add(struct shrinker *shrinker)
char buf[128]; char buf[128];
int id; int id;
lockdep_assert_held(&shrinker_mutex); lockdep_assert_held(&shrinker_rwsem);
/* debugfs isn't initialized yet, add debugfs entries later. */ /* debugfs isn't initialized yet, add debugfs entries later. */
if (!shrinker_debugfs_root) if (!shrinker_debugfs_root)
@ -211,7 +211,7 @@ int shrinker_debugfs_rename(struct shrinker *shrinker, const char *fmt, ...)
if (!new) if (!new)
return -ENOMEM; return -ENOMEM;
mutex_lock(&shrinker_mutex); down_write(&shrinker_rwsem);
old = shrinker->name; old = shrinker->name;
shrinker->name = new; shrinker->name = new;
@ -229,7 +229,7 @@ int shrinker_debugfs_rename(struct shrinker *shrinker, const char *fmt, ...)
shrinker->debugfs_entry = entry; shrinker->debugfs_entry = entry;
} }
mutex_unlock(&shrinker_mutex); up_write(&shrinker_rwsem);
kfree_const(old); kfree_const(old);
@ -242,7 +242,7 @@ struct dentry *shrinker_debugfs_detach(struct shrinker *shrinker,
{ {
struct dentry *entry = shrinker->debugfs_entry; struct dentry *entry = shrinker->debugfs_entry;
lockdep_assert_held(&shrinker_mutex); lockdep_assert_held(&shrinker_rwsem);
kfree_const(shrinker->name); kfree_const(shrinker->name);
shrinker->name = NULL; shrinker->name = NULL;
@ -271,14 +271,14 @@ static int __init shrinker_debugfs_init(void)
shrinker_debugfs_root = dentry; shrinker_debugfs_root = dentry;
/* Create debugfs entries for shrinkers registered at boot */ /* Create debugfs entries for shrinkers registered at boot */
mutex_lock(&shrinker_mutex); down_write(&shrinker_rwsem);
list_for_each_entry(shrinker, &shrinker_list, list) list_for_each_entry(shrinker, &shrinker_list, list)
if (!shrinker->debugfs_entry) { if (!shrinker->debugfs_entry) {
ret = shrinker_debugfs_add(shrinker); ret = shrinker_debugfs_add(shrinker);
if (ret) if (ret)
break; break;
} }
mutex_unlock(&shrinker_mutex); up_write(&shrinker_rwsem);
return ret; return ret;
} }

34
mm/vmscan.c
View File

@ -35,7 +35,7 @@
#include <linux/cpuset.h> #include <linux/cpuset.h>
#include <linux/compaction.h> #include <linux/compaction.h>
#include <linux/notifier.h> #include <linux/notifier.h>
#include <linux/mutex.h> #include <linux/rwsem.h>
#include <linux/delay.h> #include <linux/delay.h>
#include <linux/kthread.h> #include <linux/kthread.h>
#include <linux/freezer.h> #include <linux/freezer.h>
@ -191,7 +191,7 @@ struct scan_control {
int vm_swappiness = 60; int vm_swappiness = 60;
LIST_HEAD(shrinker_list); LIST_HEAD(shrinker_list);
DEFINE_MUTEX(shrinker_mutex); DECLARE_RWSEM(shrinker_rwsem);
DEFINE_SRCU(shrinker_srcu); DEFINE_SRCU(shrinker_srcu);
static atomic_t shrinker_srcu_generation = ATOMIC_INIT(0); static atomic_t shrinker_srcu_generation = ATOMIC_INIT(0);
@ -214,7 +214,7 @@ static struct shrinker_info *shrinker_info_protected(struct mem_cgroup *memcg,
{ {
return srcu_dereference_check(memcg->nodeinfo[nid]->shrinker_info, return srcu_dereference_check(memcg->nodeinfo[nid]->shrinker_info,
&shrinker_srcu, &shrinker_srcu,
lockdep_is_held(&shrinker_mutex)); lockdep_is_held(&shrinker_rwsem));
} }
static struct shrinker_info *shrinker_info_srcu(struct mem_cgroup *memcg, static struct shrinker_info *shrinker_info_srcu(struct mem_cgroup *memcg,
@ -293,7 +293,7 @@ int alloc_shrinker_info(struct mem_cgroup *memcg)
int nid, size, ret = 0; int nid, size, ret = 0;
int map_size, defer_size = 0; int map_size, defer_size = 0;
mutex_lock(&shrinker_mutex); down_write(&shrinker_rwsem);
map_size = shrinker_map_size(shrinker_nr_max); map_size = shrinker_map_size(shrinker_nr_max);
defer_size = shrinker_defer_size(shrinker_nr_max); defer_size = shrinker_defer_size(shrinker_nr_max);
size = map_size + defer_size; size = map_size + defer_size;
@ -309,7 +309,7 @@ int alloc_shrinker_info(struct mem_cgroup *memcg)
info->map_nr_max = shrinker_nr_max; info->map_nr_max = shrinker_nr_max;
rcu_assign_pointer(memcg->nodeinfo[nid]->shrinker_info, info); rcu_assign_pointer(memcg->nodeinfo[nid]->shrinker_info, info);
} }
mutex_unlock(&shrinker_mutex); up_write(&shrinker_rwsem);
return ret; return ret;
} }
@ -325,7 +325,7 @@ static int expand_shrinker_info(int new_id)
if (!root_mem_cgroup) if (!root_mem_cgroup)
goto out; goto out;
lockdep_assert_held(&shrinker_mutex); lockdep_assert_held(&shrinker_rwsem);
map_size = shrinker_map_size(new_nr_max); map_size = shrinker_map_size(new_nr_max);
defer_size = shrinker_defer_size(new_nr_max); defer_size = shrinker_defer_size(new_nr_max);
@ -375,7 +375,7 @@ static int prealloc_memcg_shrinker(struct shrinker *shrinker)
if (mem_cgroup_disabled()) if (mem_cgroup_disabled())
return -ENOSYS; return -ENOSYS;
mutex_lock(&shrinker_mutex); down_write(&shrinker_rwsem);
id = idr_alloc(&shrinker_idr, shrinker, 0, 0, GFP_KERNEL); id = idr_alloc(&shrinker_idr, shrinker, 0, 0, GFP_KERNEL);
if (id < 0) if (id < 0)
goto unlock; goto unlock;
@ -389,7 +389,7 @@ static int prealloc_memcg_shrinker(struct shrinker *shrinker)
shrinker->id = id; shrinker->id = id;
ret = 0; ret = 0;
unlock: unlock:
mutex_unlock(&shrinker_mutex); up_write(&shrinker_rwsem);
return ret; return ret;
} }
@ -399,7 +399,7 @@ static void unregister_memcg_shrinker(struct shrinker *shrinker)
BUG_ON(id < 0); BUG_ON(id < 0);
lockdep_assert_held(&shrinker_mutex); lockdep_assert_held(&shrinker_rwsem);
idr_remove(&shrinker_idr, id); idr_remove(&shrinker_idr, id);
} }
@ -434,7 +434,7 @@ void reparent_shrinker_deferred(struct mem_cgroup *memcg)
parent = root_mem_cgroup; parent = root_mem_cgroup;
/* Prevent from concurrent shrinker_info expand */ /* Prevent from concurrent shrinker_info expand */
mutex_lock(&shrinker_mutex); down_write(&shrinker_rwsem);
for_each_node(nid) { for_each_node(nid) {
child_info = shrinker_info_protected(memcg, nid); child_info = shrinker_info_protected(memcg, nid);
parent_info = shrinker_info_protected(parent, nid); parent_info = shrinker_info_protected(parent, nid);
@ -443,7 +443,7 @@ void reparent_shrinker_deferred(struct mem_cgroup *memcg)
atomic_long_add(nr, &parent_info->nr_deferred[i]); atomic_long_add(nr, &parent_info->nr_deferred[i]);
} }
} }
mutex_unlock(&shrinker_mutex); up_write(&shrinker_rwsem);
} }
static bool cgroup_reclaim(struct scan_control *sc) static bool cgroup_reclaim(struct scan_control *sc)
@ -744,9 +744,9 @@ void free_prealloced_shrinker(struct shrinker *shrinker)
shrinker->name = NULL; shrinker->name = NULL;
#endif #endif
if (shrinker->flags & SHRINKER_MEMCG_AWARE) { if (shrinker->flags & SHRINKER_MEMCG_AWARE) {
mutex_lock(&shrinker_mutex); down_write(&shrinker_rwsem);
unregister_memcg_shrinker(shrinker); unregister_memcg_shrinker(shrinker);
mutex_unlock(&shrinker_mutex); up_write(&shrinker_rwsem);
return; return;
} }
@ -756,11 +756,11 @@ void free_prealloced_shrinker(struct shrinker *shrinker)
void register_shrinker_prepared(struct shrinker *shrinker) void register_shrinker_prepared(struct shrinker *shrinker)
{ {
mutex_lock(&shrinker_mutex); down_write(&shrinker_rwsem);
list_add_tail_rcu(&shrinker->list, &shrinker_list); list_add_tail_rcu(&shrinker->list, &shrinker_list);
shrinker->flags |= SHRINKER_REGISTERED; shrinker->flags |= SHRINKER_REGISTERED;
shrinker_debugfs_add(shrinker); shrinker_debugfs_add(shrinker);
mutex_unlock(&shrinker_mutex); up_write(&shrinker_rwsem);
} }
static int __register_shrinker(struct shrinker *shrinker) static int __register_shrinker(struct shrinker *shrinker)
@ -811,13 +811,13 @@ void unregister_shrinker(struct shrinker *shrinker)
if (!(shrinker->flags & SHRINKER_REGISTERED)) if (!(shrinker->flags & SHRINKER_REGISTERED))
return; return;
mutex_lock(&shrinker_mutex); down_write(&shrinker_rwsem);
list_del_rcu(&shrinker->list); list_del_rcu(&shrinker->list);
shrinker->flags &= ~SHRINKER_REGISTERED; shrinker->flags &= ~SHRINKER_REGISTERED;
if (shrinker->flags & SHRINKER_MEMCG_AWARE) if (shrinker->flags & SHRINKER_MEMCG_AWARE)
unregister_memcg_shrinker(shrinker); unregister_memcg_shrinker(shrinker);
debugfs_entry = shrinker_debugfs_detach(shrinker, &debugfs_id); debugfs_entry = shrinker_debugfs_detach(shrinker, &debugfs_id);
mutex_unlock(&shrinker_mutex); up_write(&shrinker_rwsem);
atomic_inc(&shrinker_srcu_generation); atomic_inc(&shrinker_srcu_generation);
synchronize_srcu(&shrinker_srcu); synchronize_srcu(&shrinker_srcu);