Re: [PATCH] fs: hide file and bfile caches behind runtime const machinery

[Jan Kara]

On Sat 28-03-26 18:37:28, Mateusz Guzik wrote:
> s/cachep/cache/ for consistency with namei and dentry caches.
> 
> Signed-off-by: Mateusz Guzik <mjguzik@xxxxxxxxx>

Looks good. Feel free to add:

Reviewed-by: Jan Kara <jack@xxxxxxx>

								Honza

> ---
>  fs/file.c                         |  2 +-
>  fs/file_table.c                   | 31 +++++++++++++++++++------------
>  include/asm-generic/vmlinux.lds.h |  4 +++-
>  3 files changed, 23 insertions(+), 14 deletions(-)
> 
> diff --git a/fs/file.c b/fs/file.c
> index 384c83ce768d..2c81c0b162d0 100644
> --- a/fs/file.c
> +++ b/fs/file.c
> @@ -200,7 +200,7 @@ static struct fdtable *alloc_fdtable(unsigned int slots_wanted)
>  	/*
>  	 * Check if the allocation size would exceed INT_MAX. kvmalloc_array()
>  	 * and kvmalloc() will warn if the allocation size is greater than
> -	 * INT_MAX, as filp_cachep objects are not __GFP_NOWARN.
> +	 * INT_MAX, as filp_cache objects are not __GFP_NOWARN.
>  	 *
>  	 * This can happen when sysctl_nr_open is set to a very high value and
>  	 * a process tries to use a file descriptor near that limit. For example,
> diff --git a/fs/file_table.c b/fs/file_table.c
> index aaa5faaace1e..c40ec1be2899 100644
> --- a/fs/file_table.c
> +++ b/fs/file_table.c
> @@ -30,6 +30,8 @@
>  
>  #include <linux/atomic.h>
>  
> +#include <asm/runtime-const.h>
> +
>  #include "internal.h"
>  
>  /* sysctl tunables... */
> @@ -38,8 +40,10 @@ static struct files_stat_struct files_stat = {
>  };
>  
>  /* SLAB cache for file structures */
> -static struct kmem_cache *filp_cachep __ro_after_init;
> -static struct kmem_cache *bfilp_cachep __ro_after_init;
> +static struct kmem_cache *__filp_cache __ro_after_init;
> +#define filp_cache runtime_const_ptr(__filp_cache)
> +static struct kmem_cache *__bfilp_cache __ro_after_init;
> +#define bfilp_cache runtime_const_ptr(__bfilp_cache)
>  
>  static struct percpu_counter nr_files __cacheline_aligned_in_smp;
>  
> @@ -74,9 +78,9 @@ static inline void file_free(struct file *f)
>  	put_cred(f->f_cred);
>  	if (unlikely(f->f_mode & FMODE_BACKING)) {
>  		path_put(backing_file_user_path(f));
> -		kmem_cache_free(bfilp_cachep, backing_file(f));
> +		kmem_cache_free(bfilp_cache, backing_file(f));
>  	} else {
> -		kmem_cache_free(filp_cachep, f);
> +		kmem_cache_free(filp_cache, f);
>  	}
>  }
>  
> @@ -234,13 +238,13 @@ struct file *alloc_empty_file(int flags, const struct cred *cred)
>  			goto over;
>  	}
>  
> -	f = kmem_cache_alloc(filp_cachep, GFP_KERNEL);
> +	f = kmem_cache_alloc(filp_cache, GFP_KERNEL);
>  	if (unlikely(!f))
>  		return ERR_PTR(-ENOMEM);
>  
>  	error = init_file(f, flags, cred);
>  	if (unlikely(error)) {
> -		kmem_cache_free(filp_cachep, f);
> +		kmem_cache_free(filp_cache, f);
>  		return ERR_PTR(error);
>  	}
>  
> @@ -268,13 +272,13 @@ struct file *alloc_empty_file_noaccount(int flags, const struct cred *cred)
>  	struct file *f;
>  	int error;
>  
> -	f = kmem_cache_alloc(filp_cachep, GFP_KERNEL);
> +	f = kmem_cache_alloc(filp_cache, GFP_KERNEL);
>  	if (unlikely(!f))
>  		return ERR_PTR(-ENOMEM);
>  
>  	error = init_file(f, flags, cred);
>  	if (unlikely(error)) {
> -		kmem_cache_free(filp_cachep, f);
> +		kmem_cache_free(filp_cache, f);
>  		return ERR_PTR(error);
>  	}
>  
> @@ -295,13 +299,13 @@ struct file *alloc_empty_backing_file(int flags, const struct cred *cred)
>  	struct backing_file *ff;
>  	int error;
>  
> -	ff = kmem_cache_alloc(bfilp_cachep, GFP_KERNEL);
> +	ff = kmem_cache_alloc(bfilp_cache, GFP_KERNEL);
>  	if (unlikely(!ff))
>  		return ERR_PTR(-ENOMEM);
>  
>  	error = init_file(&ff->file, flags, cred);
>  	if (unlikely(error)) {
> -		kmem_cache_free(bfilp_cachep, ff);
> +		kmem_cache_free(bfilp_cache, ff);
>  		return ERR_PTR(error);
>  	}
>  
> @@ -593,14 +597,17 @@ void __init files_init(void)
>  		.freeptr_offset = offsetof(struct file, f_freeptr),
>  	};
>  
> -	filp_cachep = kmem_cache_create("filp", sizeof(struct file), &args,
> +	__filp_cache = kmem_cache_create("filp", sizeof(struct file), &args,
>  				SLAB_HWCACHE_ALIGN | SLAB_PANIC |
>  				SLAB_ACCOUNT | SLAB_TYPESAFE_BY_RCU);
> +	runtime_const_init(ptr, __filp_cache);
>  
>  	args.freeptr_offset = offsetof(struct backing_file, bf_freeptr);
> -	bfilp_cachep = kmem_cache_create("bfilp", sizeof(struct backing_file),
> +	__bfilp_cache = kmem_cache_create("bfilp", sizeof(struct backing_file),
>  				&args, SLAB_HWCACHE_ALIGN | SLAB_PANIC |
>  				SLAB_ACCOUNT | SLAB_TYPESAFE_BY_RCU);
> +	runtime_const_init(ptr, __bfilp_cache);
> +
>  	percpu_counter_init(&nr_files, 0, GFP_KERNEL);
>  }
>  
> diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
> index 1e1580febe4b..4f8e734c4336 100644
> --- a/include/asm-generic/vmlinux.lds.h
> +++ b/include/asm-generic/vmlinux.lds.h
> @@ -975,7 +975,9 @@
>  		RUNTIME_CONST(shift, d_hash_shift)			\
>  		RUNTIME_CONST(ptr, dentry_hashtable)			\
>  		RUNTIME_CONST(ptr, __dentry_cache)			\
> -		RUNTIME_CONST(ptr, __names_cache)
> +		RUNTIME_CONST(ptr, __names_cache)			\
> +		RUNTIME_CONST(ptr, __filp_cache)			\
> +		RUNTIME_CONST(ptr, __bfilp_cache)
>  
>  /* Alignment must be consistent with (kunit_suite *) in include/kunit/test.h */
>  #define KUNIT_TABLE()							\
> -- 
> 2.48.1
> 
-- 
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR