From 332f606b32b6291a944c8cf23b91f53a6e676525 Mon Sep 17 00:00:00 2001 From: Miklos Szeredi Date: Wed, 18 Aug 2021 22:08:24 +0200 Subject: 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 Signed-off-by: Miklos Szeredi --- fs/posix_acl.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) (limited to 'fs/posix_acl.c') 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 #include #include +#include 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); -- cgit v1.2.3