Messages in this thread | | | Date | Thu, 27 Jul 2023 16:55:27 +0800 | Subject | Re: [PATCH v3 28/49] dm zoned: dynamically allocate the dm-zoned-meta shrinker | From | Qi Zheng <> |
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Hi,
On 2023/7/27 16:30, Damien Le Moal wrote: > 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.arch@bytedance.com> >> Reviewed-by: Muchun Song <songmuchun@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.
Indeed, will fix.
>> 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.
In some registration scenarios, memory needs to be allocated in advance. So we continue to use the previous prealloc/register_prepared() algorithm. The shrinker_alloc_and_register() is just a helper function that combines the two, and this increases the number of APIs that shrinker exposes to the outside, so I choose not to add this helper.
Thanks, Qi
> >> + >> 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); >> } >
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