On 8/28/24 12:56, Christian Brauner wrote:
> Switch to the new kmem_cache_create_rcu() helper which allows us to use
> a custom free pointer offset avoiding the need to have an external free
> pointer which would grow struct file behind our backs.
>
> Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx>
Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx>
> ---
> fs/file_table.c | 6 +++---
> include/linux/fs.h | 2 ++
> 2 files changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/fs/file_table.c b/fs/file_table.c
> index 694199a1a966..83d5ac1fadc0 100644
> --- a/fs/file_table.c
> +++ b/fs/file_table.c
> @@ -514,9 +514,9 @@ EXPORT_SYMBOL(__fput_sync);
>
> void __init files_init(void)
> {
> - filp_cachep = kmem_cache_create("filp", sizeof(struct file), 0,
> - SLAB_TYPESAFE_BY_RCU | SLAB_HWCACHE_ALIGN |
> - SLAB_PANIC | SLAB_ACCOUNT, NULL);
> + filp_cachep = kmem_cache_create_rcu("filp", sizeof(struct file),
> + offsetof(struct file, f_freeptr),
> + SLAB_HWCACHE_ALIGN | SLAB_PANIC | SLAB_ACCOUNT);
> percpu_counter_init(&nr_files, 0, GFP_KERNEL);
> }
>
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 61097a9cf317..5ca83e87adef 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -1026,6 +1026,7 @@ static inline int ra_has_index(struct file_ra_state *ra, pgoff_t index)
> * @f_task_work: task work entry point
> * @f_llist: work queue entrypoint
> * @f_ra: file's readahead state
> + * @f_freeptr: Pointer used by SLAB_TYPESAFE_BY_RCU file cache (don't touch.)
> */
> struct file {
> atomic_long_t f_count;
> @@ -1057,6 +1058,7 @@ struct file {
> struct callback_head f_task_work;
> struct llist_node f_llist;
> struct file_ra_state f_ra;
> + freeptr_t f_freeptr;
> };
> /* --- cacheline 3 boundary (192 bytes) --- */
> } __randomize_layout
>
