Commit ea566e18 authored Aug 28, 2024 by Christian Brauner

fs: use kmem_cache_create_rcu()

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.

Link: https://lore.kernel.org/r/20240828-work-kmem_cache-rcu-v3-3-5460bc1f09f6@kernel.org

Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>

parent d345bd2e

fs/file_table.c

+3 −3

Original line number	Diff line number	Diff line
		@@ -511,9 +511,9 @@ 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);
		}

include/linux/fs.h

+2 −0

Original line number	Diff line number	Diff line
		@@ -1011,6 +1011,7 @@ 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;
		@@ -1042,6 +1043,7 @@ 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