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SubjectRe: [PATCH] fs: filp_cachep can be static in fs/file_table.c
On Tue, Dec 09, 2008 at 11:48:45PM +0100, Eric Dumazet wrote:
> Hi Andrew
>
> Please find two cleanups before patch re-submission to use
> SLAB_DESTROY_BY_RCU for "struct file".
>
> Thank you
>
> [PATCH] fs: filp_cachep can be static in fs/file_table.c
>
> 1) Documentation cleanup
>
> Documentation/filesystems/files.txt was not updated when
> f_count became an atomic_long_t.
> atomic_long_inc_not_zero() is now used instead of atomic_inc_not_zero()
>
> 2) filp_cachep can be static to fs/file_table.c
>
> Instead of creating the "filp" kmem_cache in vfs_caches_init(),
> we can do it a litle be later in files_init(), so that filp_cachep
> is static to fs/file_table.c

Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

> Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
> ---
> Documentation/filesystems/files.txt | 6 +++---
> fs/dcache.c | 6 ------
> fs/file_table.c | 10 +++++++++-
> include/linux/fdtable.h | 2 --
> 4 files changed, 12 insertions(+), 12 deletions(-)
>
> diff --git a/Documentation/filesystems/files.txt b/Documentation/filesystems/files.txt
> index bb0142f..ac2facc 100644
> --- a/Documentation/filesystems/files.txt
> +++ b/Documentation/filesystems/files.txt
> @@ -76,13 +76,13 @@ the fdtable structure -
> 5. Handling of the file structures is special. Since the look-up
> of the fd (fget()/fget_light()) are lock-free, it is possible
> that look-up may race with the last put() operation on the
> - file structure. This is avoided using atomic_inc_not_zero()
> + file structure. This is avoided using atomic_long_inc_not_zero()
> on ->f_count :
>
> rcu_read_lock();
> file = fcheck_files(files, fd);
> if (file) {
> - if (atomic_inc_not_zero(&file->f_count))
> + if (atomic_long_inc_not_zero(&file->f_count))
> *fput_needed = 1;
> else
> /* Didn't get the reference, someone's freed */
> @@ -92,7 +92,7 @@ the fdtable structure -
> ....
> return file;
>
> - atomic_inc_not_zero() detects if refcounts is already zero or
> + atomic_long_inc_not_zero() detects if refcounts is already zero or
> goes to zero during increment. If it does, we fail
> fget()/fget_light().
>
> diff --git a/fs/dcache.c b/fs/dcache.c
> index a1d86c7..fa1ba03 100644
> --- a/fs/dcache.c
> +++ b/fs/dcache.c
> @@ -2313,9 +2313,6 @@ static void __init dcache_init(void)
> /* SLAB cache for __getname() consumers */
> struct kmem_cache *names_cachep __read_mostly;
>
> -/* SLAB cache for file structures */
> -struct kmem_cache *filp_cachep __read_mostly;
> -
> EXPORT_SYMBOL(d_genocide);
>
> void __init vfs_caches_init_early(void)
> @@ -2337,9 +2334,6 @@ void __init vfs_caches_init(unsigned long mempages)
> names_cachep = kmem_cache_create("names_cache", PATH_MAX, 0,
> SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
>
> - filp_cachep = kmem_cache_create("filp", sizeof(struct file), 0,
> - SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
> -
> dcache_init();
> inode_init();
> files_init(mempages);
> diff --git a/fs/file_table.c b/fs/file_table.c
> index 5ad0eca..a46e880 100644
> --- a/fs/file_table.c
> +++ b/fs/file_table.c
> @@ -32,6 +32,9 @@ struct files_stat_struct files_stat = {
> /* public. Not pretty! */
> __cacheline_aligned_in_smp DEFINE_SPINLOCK(files_lock);
>
> +/* SLAB cache for file structures */
> +static struct kmem_cache *filp_cachep __read_mostly;
> +
> static struct percpu_counter nr_files __cacheline_aligned_in_smp;
>
> static inline void file_free_rcu(struct rcu_head *head)
> @@ -397,7 +400,12 @@ too_bad:
> void __init files_init(unsigned long mempages)
> {
> int n;
> - /* One file with associated inode and dcache is very roughly 1K.
> +
> + filp_cachep = kmem_cache_create("filp", sizeof(struct file), 0,
> + SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);
> +
> + /*
> + * One file with associated inode and dcache is very roughly 1K.
> * Per default don't use more than 10% of our memory for files.
> */
>
> diff --git a/include/linux/fdtable.h b/include/linux/fdtable.h
> index 4aab6f1..09d6c5b 100644
> --- a/include/linux/fdtable.h
> +++ b/include/linux/fdtable.h
> @@ -57,8 +57,6 @@ struct files_struct {
>
> #define files_fdtable(files) (rcu_dereference((files)->fdt))
>
> -extern struct kmem_cache *filp_cachep;
> -
> struct file_operations;
> struct vfsmount;
> struct dentry;
> --
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