[PATCH v6 30/45] ext4: dynamically allocate the ext4-es shrinker

Qi Zheng
2023-09-11T21:17:37Z

In preparation for implementing lockless slab shrink, use new APIs to
dynamically allocate the ext4-es shrinker, so that it can be freed
asynchronously via RCU. Then it doesn't need to wait for RCU read-side
critical section when releasing the struct ext4_sb_info.

Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
CC: "Theodore Ts'o" <tytso@mit.edu>
CC: Andreas Dilger <adilger.kernel@dilger.ca>
CC: linux-ext4@vger.kernel.org
---
fs/ext4/ext4.h | 2 +-
fs/ext4/extents_status.c | 23 +++++++++++++----------
2 files changed, 14 insertions(+), 11 deletions(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 9418359b1d9d..8eeff770992c 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1653,7 +1653,7 @@ struct ext4_sb_info {
__u32 s_csum_seed;

/* Reclaim extents from extent status tree */
- struct shrinker s_es_shrinker;
+ struct shrinker *s_es_shrinker;
struct list_head s_es_list; /* List of inodes with reclaimable extents */
long s_es_nr_inode;
struct ext4_es_stats s_es_stats;
diff --git a/fs/ext4/extents_status.c b/fs/ext4/extents_status.c
index 6f7de14c0fa8..deec7d1f4e50 100644
--- a/fs/ext4/extents_status.c
+++ b/fs/ext4/extents_status.c
@@ -1606,7 +1606,7 @@ static unsigned long ext4_es_count(struct shrinker *shrink,
unsigned long nr;
struct ext4_sb_info *sbi;

- sbi = container_of(shrink, struct ext4_sb_info, s_es_shrinker);
+ sbi = shrink->private_data;
nr = percpu_counter_read_positive(&sbi->s_es_stats.es_stats_shk_cnt);
trace_ext4_es_shrink_count(sbi->s_sb, sc->nr_to_scan, nr);
return nr;
@@ -1615,8 +1615,7 @@ static unsigned long ext4_es_count(struct shrinker *shrink,
static unsigned long ext4_es_scan(struct shrinker *shrink,
struct shrink_control *sc)
{
- struct ext4_sb_info *sbi = container_of(shrink,
- struct ext4_sb_info, s_es_shrinker);
+ struct ext4_sb_info *sbi = shrink->private_data;
int nr_to_scan = sc->nr_to_scan;
int ret, nr_shrunk;

@@ -1700,13 +1699,17 @@ int ext4_es_register_shrinker(struct ext4_sb_info *sbi)
if (err)
goto err3;

- sbi->s_es_shrinker.scan_objects = ext4_es_scan;
- sbi->s_es_shrinker.count_objects = ext4_es_count;
- sbi->s_es_shrinker.seeks = DEFAULT_SEEKS;
- err = register_shrinker(&sbi->s_es_shrinker, "ext4-es:%s",
- sbi->s_sb->s_id);
- if (err)
+ sbi->s_es_shrinker = shrinker_alloc(0, "ext4-es:%s", sbi->s_sb->s_id);
+ if (!sbi->s_es_shrinker) {
+ err = -ENOMEM;
goto err4;
+ }
+
+ sbi->s_es_shrinker->scan_objects = ext4_es_scan;
+ sbi->s_es_shrinker->count_objects = ext4_es_count;
+ sbi->s_es_shrinker->private_data = sbi;
+
+ shrinker_register(sbi->s_es_shrinker);

return 0;
err4:
@@ -1726,7 +1729,7 @@ void ext4_es_unregister_shrinker(struct ext4_sb_info *sbi)
percpu_counter_destroy(&sbi->s_es_stats.es_stats_cache_misses);
percpu_counter_destroy(&sbi->s_es_stats.es_stats_all_cnt);
percpu_counter_destroy(&sbi->s_es_stats.es_stats_shk_cnt);
- unregister_shrinker(&sbi->s_es_shrinker);
+ shrinker_free(sbi->s_es_shrinker);
}

/*
--
2.30.2