[PATCH RFC v3 12/13] mm: add SLAB_TYPESAFE_BY_RCU to files_cache

[Andrii Nakryiko]

Add RCU protection for file struct's backing memory by adding
SLAB_TYPESAFE_BY_RCU flag to files_cachep. This will allow to locklessly
access struct file's fields under RCU lock protection without having to
take much more expensive and contended locks.

This is going to be used for lockless uprobe look up in the next patch.

Suggested-by: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
---
 kernel/fork.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/fork.c b/kernel/fork.c
index 76ebafb956a6..91ecc32a491c 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -3157,8 +3157,8 @@ void __init proc_caches_init(void)
 			NULL);
 	files_cachep = kmem_cache_create("files_cache",
 			sizeof(struct files_struct), 0,
-			SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
-			NULL);
+			SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_TYPESAFE_BY_RCU|
+			SLAB_ACCOUNT, NULL);
 	fs_cachep = kmem_cache_create("fs_cache",
 			sizeof(struct fs_struct), 0,
 			SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT,
-- 
2.43.5