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 <[email protected]>
>> Reviewed-by: Muchun Song <[email protected]>
>> ---
>> 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);
>> }
>
On 7/27/23 17:55, Qi Zheng wrote:
>>> 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.
And that results in more code in many places instead of less code + a simple
inline helper in the shrinker header file... So not adding that super simple
helper is not exactly the best choice in my opinion.
--
Damien Le Moal
Western Digital Research
On 2023/7/27 18:20, Damien Le Moal wrote:
> On 7/27/23 17:55, Qi Zheng wrote:
>>>> 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.
>
> And that results in more code in many places instead of less code + a simple
> inline helper in the shrinker header file... So not adding that super simple
It also needs to be exported to the driver for use.
> helper is not exactly the best choice in my opinion.
Hm, either one is fine for me. If no one else objects, I can add this
helper. ;)
>