On Thu, Mar 09, 2023 at 12:19:09PM +0000, Luís Henriques wrote:
> This patch introduces a new helper function which prepares an atomic_open.
> Because atomic open can act as a lookup if handed a dentry that is negative,
> we need to set DCACHE_NOKEY_NAME if the key for the parent isn't available.
>
> The reason for getting the encryption info before checking if the directory
> has the encryption key is because we may have the key available but the
> encryption info isn't yet set (maybe due to a drop_caches). The regular
> open path will use fscrypt_file_open for that but in the atomic open a
> different approach is required.
>
> Signed-off-by: Luís Henriques <lhenriques@xxxxxxx>
> ---
> fs/crypto/hooks.c | 14 ++++++++++++++
> include/linux/fscrypt.h | 6 ++++++
> 2 files changed, 20 insertions(+)
>
> diff --git a/fs/crypto/hooks.c b/fs/crypto/hooks.c
> index 7b8c5a1104b5..cbb828ecc5eb 100644
> --- a/fs/crypto/hooks.c
> +++ b/fs/crypto/hooks.c
> @@ -117,6 +117,20 @@ int __fscrypt_prepare_readdir(struct inode *dir)
> }
> EXPORT_SYMBOL_GPL(__fscrypt_prepare_readdir);
>
> +int __fscrypt_prepare_atomic_open(struct inode *dir, struct dentry *dentry)
Anything exported to filesystems should have a kerneldoc comment. That would be
a good place to put some of the explanation that you currently have only in the
commit message.
Also, double-underscored functions are not for use by filesystems directly.
Normally the pattern would be to make fscrypt_prepare_atomic_open() an inline
function that checks IS_ENCRYPTED() and calls an out-of-line function
__fscrypt_prepare_atomic_open(). But if it happens to be simpler to make the
caller handle the IS_ENCRYPTED() check in this case, then there should simply be
one function: fscrypt_prepare_atomic_open() (no leading underscores).
> +{
> + int err = fscrypt_get_encryption_info(dir, true);
> +
> + if (err || (!err && !fscrypt_has_encryption_key(dir))) {
> + spin_lock(&dentry->d_lock);
> + dentry->d_flags |= DCACHE_NOKEY_NAME;
> + spin_unlock(&dentry->d_lock);
> + }
Why does DCACHE_NOKEY_NAME need to be set on error?
Also note that the '!err &&' part has no effect.
- Eric
