Eric Biggers <ebiggers@xxxxxxxxxx> writes:
> 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).
Thank you, Eric. I'll make sure that next rev will take these comments
into account. It definitely makes sense to move (or duplicate) the
details as a kerneldoc comment.
>> +{
>> + 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.
To be honest, I wasn't really sure that if the d_flags should be set on
error either. I'll drop that, and then the 'if' statement will make more
sense without the '||'.
Cheers
--
Luís
