On Thu, 7 Nov 2024 at 12:22, Mateusz Guzik <mjguzik@xxxxxxxxx> wrote:
>
> How about filesystems maintaing a flag: IOP_EVERYONECANTRAREVERSE?
It's actually just easier if a filesystem just does
cache_no_acl(inode);
in its read-inode function if it knows it has no ACL's.
Some filesystems already do that, eg btrfs has
/*
* try to precache a NULL acl entry for files that don't have
* any xattrs or acls
*/
....
if (!maybe_acls)
cache_no_acl(inode);
in btrfs_read_locked_inode(). If that 'maybe' is just reliable enough,
that's all it takes.
I tried to do the same thing for ext4, and failed miserably, but
that's probably because my logic for "maybe_acls" was broken since I'm
not familiar enough with ext4 at that level, and I made it do just
/* Initialize the "no ACL's" state for the simple cases */
if (!ext4_test_inode_state(inode, EXT4_STATE_XATTR) && !ei->i_file_acl)
cache_no_acl(inode);
which doesn't seem to be a strong enough text.
Linus
