Subject: Re: linux-next: build failure after merge of the bcachefs tree

From: Qi Zheng <[email-masked]>
Date: Wed, 13 Sep 2023 09:10:11 +0800

Hi Stephen,

On 2023/9/13 07:35, Stephen Rothwell wrote:
> Hi Qi,
> 
> Thanks for the corrections.  See below.
> 
> On Tue, 12 Sep 2023 10:47:14 +0800 Qi Zheng <[email-masked]> wrote:
>>
>>> diff --git a/fs/bcachefs/btree_cache.c b/fs/bcachefs/btree_cache.c
>>> index 245ddd92b2d1..7f0eded6c296 100644
>>> --- a/fs/bcachefs/btree_cache.c
>>> +++ b/fs/bcachefs/btree_cache.c
>>> @@ -285,7 +285,7 @@ static int btree_node_write_and_reclaim(struct bch_fs *c, struct btree *b)
>>>    static unsigned long bch2_btree_cache_scan(struct shrinker *shrink,
>>>    					   struct shrink_control *sc)
>>>    {
>>> -	struct bch_fs *c = container_of(shrink, struct bch_fs,
>>> +	struct bch_fs *c = container_of(&shrink, struct bch_fs,
>>>    					btree_cache.shrink);
>>
>> The shrink passed in here will be a local variable, so its address can
>> not be used directly. So need to be modified as follows:
>>
>> 	struct bch_fs *c = shrink->private_data;
> 
> OK.
> 
>>> @@ -384,7 +384,7 @@ static unsigned long bch2_btree_cache_scan(struct shrinker *shrink,
>>>    static unsigned long bch2_btree_cache_count(struct shrinker *shrink,
>>>    					    struct shrink_control *sc)
>>>    {
>>> -	struct bch_fs *c = container_of(shrink, struct bch_fs,
>>> +	struct bch_fs *c = container_of(&shrink, struct bch_fs,
>>>    					btree_cache.shrink);
>>
>> Ditto.
> 
> OK
> 
>>>    > @@ -473,12 +474,14 @@ int bch2_fs_btree_cache_init(struct bch_fs *c)
>>>    >   	mutex_init(&c->verify_lock);
>>>    > -	bc->shrink.count_objects	= bch2_btree_cache_count;
>>> -	bc->shrink.scan_objects		= bch2_btree_cache_scan;
>>> -	bc->shrink.seeks		= 4;
>>> -	ret = register_shrinker(&bc->shrink, "%s/btree_cache", c->name);
>>> -	if (ret)
>>> +	shrink = shrinker_alloc(0, "%s/btree_cache", c->name);
>>> +	if (!shrink)
>>>    		goto err;
>>
>> Here the 'ret' needs to be set to -ENOMEM.
>>
>> 	if (!shrink) {
>> 		ret = -ENOMEM;
>> 		goto err;
>> 	}
> 
> Except err: does this:
> 
>      return -BCH_ERR_ENOMEM_fs_btree_cache_init;
> 
> so ret does not need to be set.
> 
>>> +	bc->shrink = shrink;
>>> +	shrink->count_objects	= bch2_btree_cache_count;
>>> +	shrink->scan_objects	= bch2_btree_cache_scan;
>>> +	shrink->seeks		= 4;
>>
>> 	shrink->private_data = c;
> 
> OK
> 
>>> diff --git a/fs/bcachefs/btree_key_cache.c b/fs/bcachefs/btree_key_cache.c
>>> index 505e7c365ab7..88d33690233b 100644
>>> --- a/fs/bcachefs/btree_key_cache.c
>>> +++ b/fs/bcachefs/btree_key_cache.c
>>> @@ -838,7 +838,7 @@ void bch2_btree_key_cache_drop(struct btree_trans *trans,
>>>    static unsigned long bch2_btree_key_cache_scan(struct shrinker *shrink,
>>>    					   struct shrink_control *sc)
>>>    {
>>> -	struct bch_fs *c = container_of(shrink, struct bch_fs,
>>> +	struct bch_fs *c = container_of(&shrink, struct bch_fs,
>>>    					btree_key_cache.shrink);
>>
>> 	struct bch_fs *c = shrink->private_data;
>>
> 
> OK
> 
>>> @@ -936,7 +936,7 @@ static unsigned long bch2_btree_key_cache_scan(struct shrinker *shrink,
>>>    static unsigned long bch2_btree_key_cache_count(struct shrinker *shrink,
>>>    					    struct shrink_control *sc)
>>>    {
>>> -	struct bch_fs *c = container_of(shrink, struct bch_fs,
>>> +	struct bch_fs *c = container_of(&shrink, struct bch_fs,
>>>    					btree_key_cache.shrink);
>>
>> Ditto.
> 
> OK
> 
>>> @@ -957,7 +957,7 @@ void bch2_fs_btree_key_cache_exit(struct btree_key_cache *bc)
>>>    	int cpu;
>>>    #endif
>>>    > -	unregister_shrinker(&bc->shrink);
>>> +	shrinker_free(bc->shrink);
>>>    >   	mutex_lock(&bc->lock);
>>>    > @@ -1031,6 +1031,7 @@ void bch2_fs_btree_key_cache_init_early(struct btree_key_cache *c)
>>>    int bch2_fs_btree_key_cache_init(struct btree_key_cache *bc)
>>>    {
>>>    	struct bch_fs *c = container_of(bc, struct bch_fs, btree_key_cache);
>>> +	struct shrinker *shrink;
>>>    >   #ifdef __KERNEL__
>>>    	bc->pcpu_freed = alloc_percpu(struct btree_key_cache_freelist);
>>> @@ -1043,11 +1044,14 @@ int bch2_fs_btree_key_cache_init(struct btree_key_cache *bc)
>>
>> 	struct bch_fs *c = container_of(bc, struct bch_fs, btree_key_cache);
> 
> Already done n this function.
> 
>>>    >   	bc->table_init_done = true;
>>>    > -	bc->shrink.seeks		= 0;
>>> -	bc->shrink.count_objects	= bch2_btree_key_cache_count;
>>> -	bc->shrink.scan_objects		= bch2_btree_key_cache_scan;
>>> -	if (register_shrinker(&bc->shrink, "%s/btree_key_cache", c->name))
>>> +	shrink = shrinker_alloc(0, "%s/btree_key_cache", c->name);
>>> +	if (!shrink)
>>>    		return -BCH_ERR_ENOMEM_fs_btree_cache_init;
>>> +	bc->shrink = shrink;
>>> +	shrink->seeks		= 0;
>>> +	shrink->count_objects	= bch2_btree_key_cache_count;
>>> +	shrink->scan_objects	= bch2_btree_key_cache_scan;
>>
>> 	shrink->private_data = c;
> 
> OK
> 
> So the merge resolution patch now looks like this:
> 
> From: Stephen Rothwell <[email-masked]>
> Date: Tue, 12 Sep 2023 11:27:22 +1000
> Subject: [PATCH] bcachefs: convert to dynamically allocated shrinkers
> 
> Signed-off-by: Stephen Rothwell <[email-masked]>
> ---
>   fs/bcachefs/btree_cache.c     | 22 ++++++++++++----------
>   fs/bcachefs/btree_key_cache.c | 21 ++++++++++++---------
>   fs/bcachefs/btree_types.h     |  4 ++--
>   fs/bcachefs/fs.c              |  2 +-
>   fs/bcachefs/sysfs.c           |  2 +-
>   5 files changed, 28 insertions(+), 23 deletions(-)

This version looks good to me.

Reviewed-by: Qi Zheng <[email-masked]>

Thanks,
Qi

> 
> diff --git a/fs/bcachefs/btree_cache.c b/fs/bcachefs/btree_cache.c
> index 245ddd92b2d1..d8cd0bbc33cc 100644
> --- a/fs/bcachefs/btree_cache.c
> +++ b/fs/bcachefs/btree_cache.c
> @@ -285,8 +285,7 @@ static int btree_node_write_and_reclaim(struct bch_fs *c, struct btree *b)
>   static unsigned long bch2_btree_cache_scan(struct shrinker *shrink,
>   					   struct shrink_control *sc)
>   {
> -	struct bch_fs *c = container_of(shrink, struct bch_fs,
> -					btree_cache.shrink);
> +	struct bch_fs *c = shrink->private_data;
>   	struct btree_cache *bc = &c->btree_cache;
>   	struct btree *b, *t;
>   	unsigned long nr = sc->nr_to_scan;
> @@ -384,8 +383,7 @@ static unsigned long bch2_btree_cache_scan(struct shrinker *shrink,
>   static unsigned long bch2_btree_cache_count(struct shrinker *shrink,
>   					    struct shrink_control *sc)
>   {
> -	struct bch_fs *c = container_of(shrink, struct bch_fs,
> -					btree_cache.shrink);
> +	struct bch_fs *c = shrink->private_data;
>   	struct btree_cache *bc = &c->btree_cache;
>   
>   	if (bch2_btree_shrinker_disabled)
> @@ -400,7 +398,7 @@ void bch2_fs_btree_cache_exit(struct bch_fs *c)
>   	struct btree *b;
>   	unsigned i, flags;
>   
> -	unregister_shrinker(&bc->shrink);
> +	shrinker_free(bc->shrink);
>   
>   	/* vfree() can allocate memory: */
>   	flags = memalloc_nofs_save();
> @@ -454,6 +452,7 @@ void bch2_fs_btree_cache_exit(struct bch_fs *c)
>   int bch2_fs_btree_cache_init(struct bch_fs *c)
>   {
>   	struct btree_cache *bc = &c->btree_cache;
> +	struct shrinker *shrink;
>   	unsigned i;
>   	int ret = 0;
>   
> @@ -473,12 +472,15 @@ int bch2_fs_btree_cache_init(struct bch_fs *c)
>   
>   	mutex_init(&c->verify_lock);
>   
> -	bc->shrink.count_objects	= bch2_btree_cache_count;
> -	bc->shrink.scan_objects		= bch2_btree_cache_scan;
> -	bc->shrink.seeks		= 4;
> -	ret = register_shrinker(&bc->shrink, "%s/btree_cache", c->name);
> -	if (ret)
> +	shrink = shrinker_alloc(0, "%s/btree_cache", c->name);
> +	if (!shrink)
>   		goto err;
> +	bc->shrink = shrink;
> +	shrink->count_objects	= bch2_btree_cache_count;
> +	shrink->scan_objects	= bch2_btree_cache_scan;
> +	shrink->seeks		= 4;
> +	shrink->private_data	= c;
> +	shrinker_register(shrink);
>   
>   	return 0;
>   err:
> diff --git a/fs/bcachefs/btree_key_cache.c b/fs/bcachefs/btree_key_cache.c
> index 505e7c365ab7..ed387eb915c3 100644
> --- a/fs/bcachefs/btree_key_cache.c
> +++ b/fs/bcachefs/btree_key_cache.c
> @@ -838,8 +838,7 @@ void bch2_btree_key_cache_drop(struct btree_trans *trans,
>   static unsigned long bch2_btree_key_cache_scan(struct shrinker *shrink,
>   					   struct shrink_control *sc)
>   {
> -	struct bch_fs *c = container_of(shrink, struct bch_fs,
> -					btree_key_cache.shrink);
> +	struct bch_fs *c = shrink->private_data;
>   	struct btree_key_cache *bc = &c->btree_key_cache;
>   	struct bucket_table *tbl;
>   	struct bkey_cached *ck, *t;
> @@ -936,8 +935,7 @@ static unsigned long bch2_btree_key_cache_scan(struct shrinker *shrink,
>   static unsigned long bch2_btree_key_cache_count(struct shrinker *shrink,
>   					    struct shrink_control *sc)
>   {
> -	struct bch_fs *c = container_of(shrink, struct bch_fs,
> -					btree_key_cache.shrink);
> +	struct bch_fs *c = shrink->private_data;
>   	struct btree_key_cache *bc = &c->btree_key_cache;
>   	long nr = atomic_long_read(&bc->nr_keys) -
>   		atomic_long_read(&bc->nr_dirty);
> @@ -957,7 +955,7 @@ void bch2_fs_btree_key_cache_exit(struct btree_key_cache *bc)
>   	int cpu;
>   #endif
>   
> -	unregister_shrinker(&bc->shrink);
> +	shrinker_free(bc->shrink);
>   
>   	mutex_lock(&bc->lock);
>   
> @@ -1031,6 +1029,7 @@ void bch2_fs_btree_key_cache_init_early(struct btree_key_cache *c)
>   int bch2_fs_btree_key_cache_init(struct btree_key_cache *bc)
>   {
>   	struct bch_fs *c = container_of(bc, struct bch_fs, btree_key_cache);
> +	struct shrinker *shrink;
>   
>   #ifdef __KERNEL__
>   	bc->pcpu_freed = alloc_percpu(struct btree_key_cache_freelist);
> @@ -1043,11 +1042,15 @@ int bch2_fs_btree_key_cache_init(struct btree_key_cache *bc)
>   
>   	bc->table_init_done = true;
>   
> -	bc->shrink.seeks		= 0;
> -	bc->shrink.count_objects	= bch2_btree_key_cache_count;
> -	bc->shrink.scan_objects		= bch2_btree_key_cache_scan;
> -	if (register_shrinker(&bc->shrink, "%s/btree_key_cache", c->name))
> +	shrink = shrinker_alloc(0, "%s/btree_key_cache", c->name);
> +	if (!shrink)
>   		return -BCH_ERR_ENOMEM_fs_btree_cache_init;
> +	bc->shrink = shrink;
> +	shrink->seeks		= 0;
> +	shrink->count_objects	= bch2_btree_key_cache_count;
> +	shrink->scan_objects	= bch2_btree_key_cache_scan;
> +	shrink->private_data	= c;
> +	shrinker_register(shrink);
>   	return 0;
>   }
>   
> diff --git a/fs/bcachefs/btree_types.h b/fs/bcachefs/btree_types.h
> index 70398aaa095e..fac0abdaf167 100644
> --- a/fs/bcachefs/btree_types.h
> +++ b/fs/bcachefs/btree_types.h
> @@ -163,7 +163,7 @@ struct btree_cache {
>   	unsigned		used;
>   	unsigned		reserve;
>   	atomic_t		dirty;
> -	struct shrinker		shrink;
> +	struct shrinker		*shrink;
>   
>   	/*
>   	 * If we need to allocate memory for a new btree node and that
> @@ -321,7 +321,7 @@ struct btree_key_cache {
>   	bool			table_init_done;
>   	struct list_head	freed_pcpu;
>   	struct list_head	freed_nonpcpu;
> -	struct shrinker		shrink;
> +	struct shrinker		*shrink;
>   	unsigned		shrink_iter;
>   	struct btree_key_cache_freelist __percpu *pcpu_freed;
>   
> diff --git a/fs/bcachefs/fs.c b/fs/bcachefs/fs.c
> index 48431700b83e..bdc8573631bd 100644
> --- a/fs/bcachefs/fs.c
> +++ b/fs/bcachefs/fs.c
> @@ -1885,7 +1885,7 @@ static struct dentry *bch2_mount(struct file_system_type *fs_type,
>   		sb->s_flags	|= SB_POSIXACL;
>   #endif
>   
> -	sb->s_shrink.seeks = 0;
> +	sb->s_shrink->seeks = 0;
>   
>   	vinode = bch2_vfs_inode_get(c, BCACHEFS_ROOT_SUBVOL_INUM);
>   	ret = PTR_ERR_OR_ZERO(vinode);
> diff --git a/fs/bcachefs/sysfs.c b/fs/bcachefs/sysfs.c
> index 41c6900c34c1..a9f480c26bb4 100644
> --- a/fs/bcachefs/sysfs.c
> +++ b/fs/bcachefs/sysfs.c
> @@ -522,7 +522,7 @@ STORE(bch2_fs)
>   
>   		sc.gfp_mask = GFP_KERNEL;
>   		sc.nr_to_scan = strtoul_or_return(buf);
> -		c->btree_cache.shrink.scan_objects(&c->btree_cache.shrink, &sc);
> +		c->btree_cache.shrink->scan_objects(c->btree_cache.shrink, &sc);
>   	}
>   
>   	if (attr == &sysfs_btree_wakeup)