Re: [PATCH 1/2] fscrypt: new helper function - fscrypt_prepare_atomic_open()

[Eric Biggers <ebiggers@kernel.org>]

On Wed, Mar 15, 2023 at 11:08:23AM +0000, Luís Henriques wrote:
> > So, actually I think this patch doesn't make sense.  If ceph is doing the above
> > in its ->lookup() anyway, then it just should do the exact same thing in its
> > ->atomic_open() too.
> 
> In fact, my initial fix for the cephfs bug was doing just that.  It was a
> single patch to ceph_atomic_open() that would simply do:
> 
> 	if (IS_ENCRYPTED(dir)) {
> 		set_bit(CEPH_MDS_R_FSCRYPT_FILE, &req->r_req_flags);
> 		err = __fscrypt_prepare_readdir(dir);
> 		if (!err && !fscrypt_has_encryption_key(dir)) {
> 			spin_lock(&dentry->d_lock);
> 			dentry->d_flags |= DCACHE_NOKEY_NAME;
> 			spin_unlock(&dentry->d_lock);
> 		}
> 	}
> 
> What made me want to create a new helper was that I simply needed to call
> fscrypt_get_encryption_info() to force the encryption info to be set in
> the parent directory.  But this function was only accessible through
> __fscrypt_prepare_readdir(), which isn't really a great function name for
> what I need here.
> 
> Since __fscrypt_prepare_readdir() doesn't seem to be used anywhere else,
> maybe it could be removed and fscrypt_get_encryption_info() be exported
> instead?

Well, fscrypt_get_encryption_info() *used* to be exported, but it was hard to
keep track of its use cases (some of which were not actually necessary), which
is why it eventually got replaced with use-case oriented helper functions.

Maybe just use fscrypt_prepare_lookup_partial() for the name of your new helper
function (instead of fscrypt_prepare_atomic_open())?

- Eric