RCUify freeing acls, let check_acl() go ahead in RCU mode if acl is cached

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 9 insertions, 9 deletions

diff --git a/include/linux/posix_acl.h b/include/linux/posix_acl.h
index a9c2fb2..b768110 100644
--- a/include/linux/posix_acl.h
+++ b/include/linux/posix_acl.h
@@ -9,6 +9,7 @@
 #define __LINUX_POSIX_ACL_H
 
 #include <linux/slab.h>
+#include <linux/rcupdate.h>
 
 #define ACL_UNDEFINED_ID	(-1)
 
@@ -38,7 +39,10 @@ struct posix_acl_entry {
 };
 
 struct posix_acl {
-	atomic_t		a_refcount;
+	union {
+		atomic_t		a_refcount;
+		struct rcu_head		a_rcu;
+	};
 	unsigned int		a_count;
 	struct posix_acl_entry	a_entries[0];
 };
@@ -65,7 +69,7 @@ static inline void
 posix_acl_release(struct posix_acl *acl)
 {
 	if (acl && atomic_dec_and_test(&acl->a_refcount))
-		kfree(acl);
+		kfree_rcu(acl, a_rcu);
 }
 
 
@@ -110,13 +114,9 @@ static inline struct posix_acl *get_cached_acl(struct inode *inode, int type)
 	return acl;
 }
 
-static inline int negative_cached_acl(struct inode *inode, int type)
+static inline struct posix_acl *get_cached_acl_rcu(struct inode *inode, int type)
 {
-	struct posix_acl **p = acl_by_type(inode, type);
-	struct posix_acl *acl = ACCESS_ONCE(*p);
-	if (acl)
-		return 0;
-	return 1;
+	return rcu_dereference(*acl_by_type(inode, type));
 }
 
 static inline void set_cached_acl(struct inode *inode,
@@ -127,7 +127,7 @@ static inline void set_cached_acl(struct inode *inode,
 	struct posix_acl *old;
 	spin_lock(&inode->i_lock);
 	old = *p;
-	*p = posix_dup_acl(acl);
+	rcu_assign_pointer(*p, posix_acl_dup(acl));
 	spin_unlock(&inode->i_lock);
 	if (old != ACL_NOT_CACHED)
 		posix_acl_release(old);