ovl: enable RCU'd ->get_acl()
Overlayfs does not cache ACL's (to avoid double caching). Instead it just calls the underlying filesystem's i_op->get_acl(), which will return the cached value, if possible. In rcu path walk, however, get_cached_acl_rcu() is employed to get the value from the cache, which will fail on overlayfs resulting in dropping out of rcu walk mode. This can result in a big performance hit in certain situations. Fix by calling ->get_acl() with rcu=true in case of ACL_DONT_CACHE (which indicates pass-through) Reported-by: garyhuang <zjh.20052005@163.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
This commit is contained in:
parent
0cad624662
commit
332f606b32
|
@ -13,6 +13,7 @@
|
|||
#include <linux/fiemap.h>
|
||||
#include <linux/fileattr.h>
|
||||
#include <linux/security.h>
|
||||
#include <linux/namei.h>
|
||||
#include "overlayfs.h"
|
||||
|
||||
|
||||
|
@ -452,12 +453,12 @@ struct posix_acl *ovl_get_acl(struct inode *inode, int type, bool rcu)
|
|||
const struct cred *old_cred;
|
||||
struct posix_acl *acl;
|
||||
|
||||
if (rcu)
|
||||
return ERR_PTR(-ECHILD);
|
||||
|
||||
if (!IS_ENABLED(CONFIG_FS_POSIX_ACL) || !IS_POSIXACL(realinode))
|
||||
return NULL;
|
||||
|
||||
if (rcu)
|
||||
return get_cached_acl_rcu(realinode, type);
|
||||
|
||||
old_cred = ovl_override_creds(inode->i_sb);
|
||||
acl = get_acl(realinode, type);
|
||||
revert_creds(old_cred);
|
||||
|
|
|
@ -22,6 +22,7 @@
|
|||
#include <linux/xattr.h>
|
||||
#include <linux/export.h>
|
||||
#include <linux/user_namespace.h>
|
||||
#include <linux/namei.h>
|
||||
|
||||
static struct posix_acl **acl_by_type(struct inode *inode, int type)
|
||||
{
|
||||
|
@ -56,7 +57,17 @@ EXPORT_SYMBOL(get_cached_acl);
|
|||
|
||||
struct posix_acl *get_cached_acl_rcu(struct inode *inode, int type)
|
||||
{
|
||||
return rcu_dereference(*acl_by_type(inode, type));
|
||||
struct posix_acl *acl = rcu_dereference(*acl_by_type(inode, type));
|
||||
|
||||
if (acl == ACL_DONT_CACHE) {
|
||||
struct posix_acl *ret;
|
||||
|
||||
ret = inode->i_op->get_acl(inode, type, LOOKUP_RCU);
|
||||
if (!IS_ERR(ret))
|
||||
acl = ret;
|
||||
}
|
||||
|
||||
return acl;
|
||||
}
|
||||
EXPORT_SYMBOL(get_cached_acl_rcu);
|
||||
|
||||
|
|
|
@ -581,6 +581,11 @@ static inline void mapping_allow_writable(struct address_space *mapping)
|
|||
|
||||
struct posix_acl;
|
||||
#define ACL_NOT_CACHED ((void *)(-1))
|
||||
/*
|
||||
* ACL_DONT_CACHE is for stacked filesystems, that rely on underlying fs to
|
||||
* cache the ACL. This also means that ->get_acl() can be called in RCU mode
|
||||
* with the LOOKUP_RCU flag.
|
||||
*/
|
||||
#define ACL_DONT_CACHE ((void *)(-3))
|
||||
|
||||
static inline struct posix_acl *
|
||||
|
|
|
@ -72,6 +72,8 @@ extern struct posix_acl *get_posix_acl(struct inode *, int);
|
|||
extern int set_posix_acl(struct user_namespace *, struct inode *, int,
|
||||
struct posix_acl *);
|
||||
|
||||
struct posix_acl *get_cached_acl_rcu(struct inode *inode, int type);
|
||||
|
||||
#ifdef CONFIG_FS_POSIX_ACL
|
||||
int posix_acl_chmod(struct user_namespace *, struct inode *, umode_t);
|
||||
extern int posix_acl_create(struct inode *, umode_t *, struct posix_acl **,
|
||||
|
@ -84,7 +86,6 @@ extern int simple_set_acl(struct user_namespace *, struct inode *,
|
|||
extern int simple_acl_create(struct inode *, struct inode *);
|
||||
|
||||
struct posix_acl *get_cached_acl(struct inode *inode, int type);
|
||||
struct posix_acl *get_cached_acl_rcu(struct inode *inode, int type);
|
||||
void set_cached_acl(struct inode *inode, int type, struct posix_acl *acl);
|
||||
void forget_cached_acl(struct inode *inode, int type);
|
||||
void forget_all_cached_acls(struct inode *inode);
|
||||
|
|
Loading…
Reference in New Issue