On Mon, Feb 12, 2024 at 09:13:14PM -0500, Gabriel Krisman Bertazi wrote:
> Finally, we need to clean the dentry->flags even for unencrypted
> dentries, so the ->d_lock might be acquired even for them.  In order to

might => must?

> diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h
> index 47567a6a4f9d..d1f17b90c30f 100644
> --- a/include/linux/fscrypt.h
> +++ b/include/linux/fscrypt.h
> @@ -951,10 +951,29 @@ static inline int fscrypt_prepare_rename(struct inode 
> *old_dir,
>  static inline void fscrypt_prepare_dentry(struct dentry *dentry,
>                                         bool is_nokey_name)
>  {
> +     /*
> +      * This code tries to only take ->d_lock when necessary to write
> +      * to ->d_flags.  We shouldn't be peeking on d_flags for
> +      * DCACHE_OP_REVALIDATE unlocked, but in the unlikely case
> +      * there is a race, the worst it can happen is that we fail to
> +      * unset DCACHE_OP_REVALIDATE and pay the cost of an extra
> +      * d_revalidate.
> +      */
>       if (is_nokey_name) {
>               spin_lock(&dentry->d_lock);
>               dentry->d_flags |= DCACHE_NOKEY_NAME;
>               spin_unlock(&dentry->d_lock);
> +     } else if (dentry->d_flags & DCACHE_OP_REVALIDATE &&
> +                dentry->d_op->d_revalidate == fscrypt_d_revalidate) {
> +             /*
> +              * Unencrypted dentries and encrypted dentries where the
> +              * key is available are always valid from fscrypt
> +              * perspective. Avoid the cost of calling
> +              * fscrypt_d_revalidate unnecessarily.
> +              */
> +             spin_lock(&dentry->d_lock);
> +             dentry->d_flags &= ~DCACHE_OP_REVALIDATE;
> +             spin_unlock(&dentry->d_lock);
>       }
>  }

Does this all get optimized out when !CONFIG_FS_ENCRYPTION?

As-is, I don't think the d_revalidate part will be optimized out.

You may need to create a !CONFIG_FS_ENCRYPTION stub explicitly.

- Eric


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