Fuse is about to join overlayfs in relying on get_acl respecting ACL_DONT_CACHE so update the documentation in get_acl to reflect that fact. The comment and this change description should give people a clue that respecting ACL_DONT_CACHE in get_acl is important, and they should audit the filesystems before removing that support. Additionaly update the comment above the call to get_acl itself and remove the wrong information that an implementation of get_acl can prevent caching by calling forget_cached_acl. Replace that with the correct information that to prevent caching all that is necessary is to set inode->i_acl = inode->i_default_acl = ACL_DONT_CACHE when the inode is initialized. Signed-off-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx> --- fs/posix_acl.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/fs/posix_acl.c b/fs/posix_acl.c index 2fd0fde16fe1..3c24fc263401 100644 --- a/fs/posix_acl.c +++ b/fs/posix_acl.c @@ -121,14 +121,17 @@ struct posix_acl *get_acl(struct inode *inode, int type) * could wait for that other task to complete its job, but it's easier * to just call ->get_acl to fetch the ACL ourself. (This is going to * be an unlikely race.) + * + * ACL_DONT_CACHE is treated as another task updating the acl and + * remains set. */ if (cmpxchg(p, ACL_NOT_CACHED, sentinel) != ACL_NOT_CACHED) /* fall through */ ; /* * Normally, the ACL returned by ->get_acl will be cached. - * A filesystem can prevent that by calling - * forget_cached_acl(inode, type) in ->get_acl. + * A filesystem can prevent that by calling setting + * inode->i_acl = inode->i_default_acl = ACL_DONT_CACHE. * * If the filesystem doesn't have a get_acl() function at all, we'll * just create the negative cache entry. -- 2.14.1
