Re: [PATCH v2 2/8] fscrypt: Drop d_revalidate if key is available

[Al Viro <viro@zeniv.linux.org.uk>]

On Fri, Dec 15, 2023 at 04:16:02PM -0500, Gabriel Krisman Bertazi wrote:
> fscrypt dentries are always valid once the key is available.  Since the
> key cannot be removed without evicting the dentry, we don't need to keep
> retrying to revalidate it.
> 
> Signed-off-by: Gabriel Krisman Bertazi <krisman@suse.de>
> ---
>  fs/crypto/fname.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/crypto/fname.c b/fs/crypto/fname.c
> index 7b3fc189593a..0457ba2d7d76 100644
> --- a/fs/crypto/fname.c
> +++ b/fs/crypto/fname.c
> @@ -591,8 +591,15 @@ int fscrypt_d_revalidate(struct dentry *dentry, unsigned int flags)
>  	 * reverting to no-key names without evicting the directory's inode
>  	 * -- which implies eviction of the dentries in the directory.
>  	 */
> -	if (!(dentry->d_flags & DCACHE_NOKEY_NAME))
> +	if (!(dentry->d_flags & DCACHE_NOKEY_NAME)) {
> +		/*
> +		 * If fscrypt is the only feature requiring
> +		 * revalidation for this dentry, we can just disable it.
> +		 */
> +		if (dentry->d_op->d_revalidate == &fscrypt_d_revalidate)

Umm...  What about ceph?  IOW, why do we care how had we gotten to that
function - directly via ->d_revalidate() or from ->d_revalidate() instance?