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

[Qi Zheng <zhengqi.arch@bytedance.com>]

Hi Stephen,

On 2023/9/12 10:04, Stephen Rothwell wrote:
> Hi all,
> 
> After merging the bcachefs tree, today's linux-next build (x86_64
> allmodconfig) failed like this:
> 
> fs/bcachefs/btree_cache.c: In function 'bch2_fs_btree_cache_exit':
> fs/bcachefs/btree_cache.c:403:9: error: implicit declaration of function 'unregister_shrinker'; did you mean 'unregister_chrdev'? [-Werror=implicit-function-declaration]
>    403 |         unregister_shrinker(&bc->shrink);
>        |         ^~~~~~~~~~~~~~~~~~~
>        |         unregister_chrdev
> fs/bcachefs/btree_cache.c: In function 'bch2_fs_btree_cache_init':
> fs/bcachefs/btree_cache.c:479:15: error: implicit declaration of function 'register_shrinker'; did you mean 'register_chrdev'? [-Werror=implicit-function-declaration]
>    479 |         ret = register_shrinker(&bc->shrink, "%s/btree_cache", c->name);
>        |               ^~~~~~~~~~~~~~~~~
>        |               register_chrdev
> cc1: all warnings being treated as errors
> 
> Caused by commits
> 
>    5ec30115c066 ("bcachefs: Initial commit")
> 
> interacting with commit
> 
>    eba045d9350d ("mm: shrinker: remove old APIs")
> 
> from v6.6-rc1.
> 
> I have applied the following merge resolution patch for today.  More may
> be needed.

Thanks for doing this! Some needed fixes below.

> 
>  From 801ad185700d9a7abcf156233b9db6cf6d831581 Mon Sep 17 00:00:00 2001
> From: Stephen Rothwell <sfr@canb.auug.org.au>
> Date: Tue, 12 Sep 2023 11:27:22 +1000
> Subject: [PATCH] bcachefs: convert to dynamically allocated shrinkers
> 
> Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
> ---
>   fs/bcachefs/btree_cache.c     | 19 +++++++++++--------
>   fs/bcachefs/btree_key_cache.c | 18 +++++++++++-------
>   fs/bcachefs/btree_types.h     |  4 ++--
>   fs/bcachefs/fs.c              |  2 +-
>   fs/bcachefs/sysfs.c           |  2 +-
>   5 files changed, 26 insertions(+), 19 deletions(-)
> 
> 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;

>   	struct btree_cache *bc = &c->btree_cache;
>   	struct btree *b, *t;
> @@ -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.

>   	struct btree_cache *bc = &c->btree_cache;
>   
> @@ -400,7 +400,7 @@ 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 +454,7 @@ 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 +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;
	}


> +	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..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;

>   	struct btree_key_cache *bc = &c->btree_key_cache;
>   	struct bucket_table *tbl;
> @@ -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.

>   	struct btree_key_cache *bc = &c->btree_key_cache;
>   	long nr = atomic_long_read(&bc->nr_keys) -
> @@ -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);

>   
>   	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)