linux-ext4 - Re: [PATCH v2 30/54] fs: change evict_dentries_for_decrypted

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Message-ID: <20250828-risse-negieren-f9a3d1526782@brauner>
Date: Thu, 28 Aug 2025 14:25:21 +0200
From: Christian Brauner <brauner@...nel.org>
To: Josef Bacik <josef@...icpanda.com>
Cc: linux-fsdevel@...r.kernel.org, linux-btrfs@...r.kernel.org, 
	kernel-team@...com, linux-ext4@...r.kernel.org, linux-xfs@...r.kernel.org, 
	viro@...iv.linux.org.uk, amir73il@...il.com
Subject: Re: [PATCH v2 30/54] fs: change evict_dentries_for_decrypted_inodes
 to use refcount

On Tue, Aug 26, 2025 at 11:39:30AM -0400, Josef Bacik wrote:
> Instead of checking for I_WILL_FREE|I_FREEING simply use the refcount to
> make sure we have a live inode.
> 
> Signed-off-by: Josef Bacik <josef@...icpanda.com>
> ---

I have no idea how the lifetime of such decrypted inodes are managed.
I suppose they don't carry a separate reference but are still somehow
safe to be accessed based on the mk_decrypted_inodes list. In any case
something must hold an i_obj_count if we want to use igrab() since I
don't see any relevant rcu protection here.

>  fs/crypto/keyring.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/crypto/keyring.c b/fs/crypto/keyring.c
> index 7557f6a88b8f..969db498149a 100644
> --- a/fs/crypto/keyring.c
> +++ b/fs/crypto/keyring.c
> @@ -956,13 +956,16 @@ static void evict_dentries_for_decrypted_inodes(struct fscrypt_master_key *mk)
>  
>  	list_for_each_entry(ci, &mk->mk_decrypted_inodes, ci_master_key_link) {
>  		inode = ci->ci_inode;
> +
>  		spin_lock(&inode->i_lock);
> -		if (inode->i_state & (I_FREEING | I_WILL_FREE | I_NEW)) {
> +		if (inode->i_state & I_NEW) {
>  			spin_unlock(&inode->i_lock);
>  			continue;
>  		}
> -		__iget(inode);
>  		spin_unlock(&inode->i_lock);
> +
> +		if (!igrab(inode))
> +			continue;
>  		spin_unlock(&mk->mk_decrypted_inodes_lock);
>  
>  		shrink_dcache_inode(inode);
> -- 
> 2.49.0
>