On 7/27/23 17:04, Qi Zheng wrote:
> In preparation for implementing lockless slab shrink, use new APIs to
> dynamically allocate the dm-zoned-meta 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 dmz_metadata.
>
> Signed-off-by: Qi Zheng <zhengqi.a...@bytedance.com>
> Reviewed-by: Muchun Song <songmuc...@bytedance.com>
> ---
> drivers/md/dm-zoned-metadata.c | 28 ++++++++++++++++------------
> 1 file changed, 16 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/md/dm-zoned-metadata.c b/drivers/md/dm-zoned-metadata.c
> index 9d3cca8e3dc9..0bcb26a43578 100644
> --- a/drivers/md/dm-zoned-metadata.c
> +++ b/drivers/md/dm-zoned-metadata.c
> @@ -187,7 +187,7 @@ struct dmz_metadata {
> struct rb_root mblk_rbtree;
> struct list_head mblk_lru_list;
> struct list_head mblk_dirty_list;
> - struct shrinker mblk_shrinker;
> + struct shrinker *mblk_shrinker;
>
> /* Zone allocation management */
> struct mutex map_lock;
> @@ -615,7 +615,7 @@ static unsigned long dmz_shrink_mblock_cache(struct
> dmz_metadata *zmd,
> static unsigned long dmz_mblock_shrinker_count(struct shrinker *shrink,
> struct shrink_control *sc)
> {
> - struct dmz_metadata *zmd = container_of(shrink, struct dmz_metadata,
> mblk_shrinker);
> + struct dmz_metadata *zmd = shrink->private_data;
>
> return atomic_read(&zmd->nr_mblks);
> }
> @@ -626,7 +626,7 @@ static unsigned long dmz_mblock_shrinker_count(struct
> shrinker *shrink,
> static unsigned long dmz_mblock_shrinker_scan(struct shrinker *shrink,
> struct shrink_control *sc)
> {
> - struct dmz_metadata *zmd = container_of(shrink, struct dmz_metadata,
> mblk_shrinker);
> + struct dmz_metadata *zmd = shrink->private_data;
> unsigned long count;
>
> spin_lock(&zmd->mblk_lock);
> @@ -2936,19 +2936,23 @@ int dmz_ctr_metadata(struct dmz_dev *dev, int num_dev,
> */
> zmd->min_nr_mblks = 2 + zmd->nr_map_blocks + zmd->zone_nr_bitmap_blocks
> * 16;
> zmd->max_nr_mblks = zmd->min_nr_mblks + 512;
> - zmd->mblk_shrinker.count_objects = dmz_mblock_shrinker_count;
> - zmd->mblk_shrinker.scan_objects = dmz_mblock_shrinker_scan;
> - zmd->mblk_shrinker.seeks = DEFAULT_SEEKS;
>
> /* Metadata cache shrinker */
> - ret = register_shrinker(&zmd->mblk_shrinker, "dm-zoned-meta:(%u:%u)",
> - MAJOR(dev->bdev->bd_dev),
> - MINOR(dev->bdev->bd_dev));
> - if (ret) {
> - dmz_zmd_err(zmd, "Register metadata cache shrinker failed");
> + zmd->mblk_shrinker = shrinker_alloc(0, "dm-zoned-meta:(%u:%u)",
> + MAJOR(dev->bdev->bd_dev),
> + MINOR(dev->bdev->bd_dev));
> + if (!zmd->mblk_shrinker) {
> + dmz_zmd_err(zmd, "Allocate metadata cache shrinker failed");
ret is not set here, so dmz_ctr_metadata() will return success. You need to add:
ret = -ENOMEM;
or something.
> goto err;
> }
>
> + zmd->mblk_shrinker->count_objects = dmz_mblock_shrinker_count;
> + zmd->mblk_shrinker->scan_objects = dmz_mblock_shrinker_scan;
> + zmd->mblk_shrinker->seeks = DEFAULT_SEEKS;
> + zmd->mblk_shrinker->private_data = zmd;
> +
> + shrinker_register(zmd->mblk_shrinker);
I fail to see how this new shrinker API is better... Why isn't there a
shrinker_alloc_and_register() function ? That would avoid adding all this code
all over the place as the new API call would be very similar to the current
shrinker_register() call with static allocation.
> +
> dmz_zmd_info(zmd, "DM-Zoned metadata version %d", zmd->sb_version);
> for (i = 0; i < zmd->nr_devs; i++)
> dmz_print_dev(zmd, i);
> @@ -2995,7 +2999,7 @@ int dmz_ctr_metadata(struct dmz_dev *dev, int num_dev,
> */
> void dmz_dtr_metadata(struct dmz_metadata *zmd)
> {
> - unregister_shrinker(&zmd->mblk_shrinker);
> + shrinker_free(zmd->mblk_shrinker);
> dmz_cleanup_metadata(zmd);
> kfree(zmd);
> }
--
Damien Le Moal
Western Digital Research
