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SubjectRe: [PATCH v3 34/49] ext4: dynamically allocate the ext4-es shrinker
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On 2023/7/27 16:04, Qi Zheng wrote:
> In preparation for implementing lockless slab shrink, use new APIs to
> dynamically allocate the ext4-es 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 ext4_sb_info.
>
> Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
> Reviewed-by: Muchun Song <songmuchun@bytedance.com>
> ---
> fs/ext4/ext4.h | 2 +-
> fs/ext4/extents_status.c | 22 ++++++++++++----------
> 2 files changed, 13 insertions(+), 11 deletions(-)
>
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index 1e2259d9967d..82397bf0b33e 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -1657,7 +1657,7 @@ 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 9b5b8951afb4..74bb64fadbc4 100644
> --- a/fs/ext4/extents_status.c
> +++ b/fs/ext4/extents_status.c
> @@ -1596,7 +1596,7 @@ 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;
> @@ -1605,8 +1605,7 @@ 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;
>
> @@ -1690,14 +1689,17 @@ 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)

Here should set err to -ENOMEM, will fix.

> goto err4;
>
> + 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;
> + sbi->s_es_shrinker->private_data = sbi;
> +
> + shrinker_register(sbi->s_es_shrinker);
> +
> return 0;
> err4:
> percpu_counter_destroy(&sbi->s_es_stats.es_stats_shk_cnt);
> @@ -1716,7 +1718,7 @@ 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);
> }
>
> /*

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