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vfs: move ACL cache lookup into generic code

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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>
This commit is contained in:
Linus Torvalds
2011-07-22 19:30:19 -07:00
committed by Al Viro
parent 3ca30d40a9
commit e77819e57f
12 changed files with 64 additions and 68 deletions
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52
fs/namei.c
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@@ -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 @@ void putname(const char *name)
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 @@ static int acl_permission_check(struct inode *inode, int mask)
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;