vfs: move ACL cache lookup into generic code
This moves logic for checking the cached ACL values from low-level
filesystems into generic code. The end result is a streamlined ACL
check that doesn't need to load the inode->i_op->check_acl pointer at
all for the common cached case.
The filesystems also don't need to check for a non-blocking RCU walk
case in their acl_check() functions, because that is all handled at a
VFS layer.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/namei.c b/fs/namei.c
index b7fad00..120efc7 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -32,6 +32,7 @@
#include <linux/fcntl.h>
#include <linux/device_cgroup.h>
#include <linux/fs_struct.h>
+#include <linux/posix_acl.h>
#include <asm/uaccess.h>
#include "internal.h"
@@ -173,12 +174,58 @@
EXPORT_SYMBOL(putname);
#endif
+static int check_acl(struct inode *inode, int mask)
+{
+ struct posix_acl *acl;
+
+ /*
+ * Under RCU walk, we cannot even do a "get_cached_acl()",
+ * because that involves locking and getting a refcount on
+ * a cached ACL.
+ *
+ * So the only case we handle during RCU walking is the
+ * case of a cached "no ACL at all", which needs no locks
+ * or refcounts.
+ */
+ if (mask & MAY_NOT_BLOCK) {
+ if (negative_cached_acl(inode, ACL_TYPE_ACCESS))
+ return -EAGAIN;
+ return -ECHILD;
+ }
+
+ acl = get_cached_acl(inode, ACL_TYPE_ACCESS);
+
+ /*
+ * A filesystem can force a ACL callback by just never
+ * filling the ACL cache. But normally you'd fill the
+ * cache either at inode instantiation time, or on the
+ * first ->check_acl call.
+ *
+ * If the filesystem doesn't have a check_acl() function
+ * at all, we'll just create the negative cache entry.
+ */
+ if (acl == ACL_NOT_CACHED) {
+ if (inode->i_op->check_acl)
+ return inode->i_op->check_acl(inode, mask);
+
+ set_cached_acl(inode, ACL_TYPE_ACCESS, NULL);
+ return -EAGAIN;
+ }
+
+ if (acl) {
+ int error = posix_acl_permission(inode, acl, mask);
+ posix_acl_release(acl);
+ return error;
+ }
+
+ return -EAGAIN;
+}
+
/*
* This does basic POSIX ACL permission checking
*/
static int acl_permission_check(struct inode *inode, int mask)
{
- int (*check_acl)(struct inode *inode, int mask);
unsigned int mode = inode->i_mode;
mask &= MAY_READ | MAY_WRITE | MAY_EXEC | MAY_NOT_BLOCK;
@@ -189,8 +236,7 @@
if (current_fsuid() == inode->i_uid)
mode >>= 6;
else {
- check_acl = inode->i_op->check_acl;
- if (IS_POSIXACL(inode) && (mode & S_IRWXG) && check_acl) {
+ if (IS_POSIXACL(inode) && (mode & S_IRWXG)) {
int error = check_acl(inode, mask);
if (error != -EAGAIN)
return error;