[PATCH v3 3/3] fs: use kmem_cache_create_rcu()

[Christian Brauner <brauner@kernel.org>]

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@kernel.org>
---
 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

-- 
2.45.2