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authorMiklos Szeredi <mszeredi@redhat.com>2021-08-18 22:08:24 +0200
committerMiklos Szeredi <mszeredi@redhat.com>2021-08-18 22:08:24 +0200
commit332f606b32b6291a944c8cf23b91f53a6e676525 (patch)
treec3a46cae0901eec40dd900a9a64c8ad1e51647ba /fs/posix_acl.c
parent0cad6246621b5887d5b33fea84219d2a71f2f99a (diff)
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>
Diffstat (limited to 'fs/posix_acl.c')
-rw-r--r--fs/posix_acl.c13
1 files changed, 12 insertions, 1 deletions
diff --git a/fs/posix_acl.c b/fs/posix_acl.c
index 4f1ef826e040..f5c25f580dd9 100644
--- a/fs/posix_acl.c
+++ b/fs/posix_acl.c
@@ -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);