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ovl: enable RCU'd ->get_acl()

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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:
Miklos Szeredi
2021-08-18 22:08:24 +02:00
parent 0cad624662
commit 332f606b32
4 changed files with 23 additions and 5 deletions
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3
include/linux/posix_acl.h
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@@ -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);