linux-kernel - Re: [PATCH] ksmbd: Use common error handling code in ksmbd_vfs_path

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Message-id: <175953064635.1793333.2429881029964457140@noble.neil.brown.name>
Date: Sat, 04 Oct 2025 08:30:46 +1000
From: NeilBrown <neilb@...mail.net>
To: "Markus Elfring" <Markus.Elfring@....de>
Cc: linux-cifs@...r.kernel.org, "Namjae Jeon" <linkinjeon@...nel.org>,
 "Sergey Senozhatsky" <senozhatsky@...omium.org>,
 "Steve French" <smfrench@...il.com>, "Tom Talpey" <tom@...pey.com>,
 "LKML" <linux-kernel@...r.kernel.org>, kernel-janitors@...r.kernel.org,
 "Stefan Metzmacher" <metze@...ba.org>
Subject:
 Re: [PATCH] ksmbd: Use common error handling code in ksmbd_vfs_path_lookup()

On Sat, 04 Oct 2025, Markus Elfring wrote:
> From: Markus Elfring <elfring@...rs.sourceforge.net>
> Date: Fri, 3 Oct 2025 20:26:56 +0200
> 
> Add a jump target so that a bit of exception handling can be better reused
> at the end of this function implementation.

I think this is a good cleanup - thanks.  But I think it could be even
better.

- rename the "path" parameter to "return_path" or similar.
- declare  struct path path __free(path_-put) = {};
- change all "path->" instances to "path."
- remove all those path_put() calls, but leave the "return xxx"
- at the point of successful return, use

   return_path->dentry = no_free_ptr(path.dentry);
   return_path->mnt = no_free_ptr(path.mnt);
   return 0;

This is based on the pattern in kern_path_parent() and
__start_removing_path().

Thanks,
NeilBrown


> 
> Signed-off-by: Markus Elfring <elfring@...rs.sourceforge.net>
> ---
>  fs/smb/server/vfs.c | 32 ++++++++++++++------------------
>  1 file changed, 14 insertions(+), 18 deletions(-)
> 
> diff --git a/fs/smb/server/vfs.c b/fs/smb/server/vfs.c
> index 891ed2dc2b73..3535655b4d86 100644
> --- a/fs/smb/server/vfs.c
> +++ b/fs/smb/server/vfs.c
> @@ -94,17 +94,13 @@ static int ksmbd_vfs_path_lookup(struct ksmbd_share_config *share_conf,
>  	if (err)
>  		return err;
>  
> -	if (unlikely(type != LAST_NORM)) {
> -		path_put(path);
> -		return -ENOENT;
> -	}
> +	if (unlikely(type != LAST_NORM))
> +		goto put_path;
>  
>  	if (do_lock) {
>  		err = mnt_want_write(path->mnt);
> -		if (err) {
> -			path_put(path);
> -			return -ENOENT;
> -		}
> +		if (err)
> +			goto put_path;
>  
>  		inode_lock_nested(path->dentry->d_inode, I_MUTEX_PARENT);
>  		d = lookup_one_qstr_excl(&last, path->dentry, 0);
> @@ -116,8 +112,7 @@ static int ksmbd_vfs_path_lookup(struct ksmbd_share_config *share_conf,
>  		}
>  		inode_unlock(path->dentry->d_inode);
>  		mnt_drop_write(path->mnt);
> -		path_put(path);
> -		return -ENOENT;
> +		goto put_path;
>  	}
>  
>  	d = lookup_noperm_unlocked(&last, path->dentry);
> @@ -125,21 +120,22 @@ static int ksmbd_vfs_path_lookup(struct ksmbd_share_config *share_conf,
>  		dput(d);
>  		d = ERR_PTR(-ENOENT);
>  	}
> -	if (IS_ERR(d)) {
> -		path_put(path);
> -		return -ENOENT;
> -	}
> +	if (IS_ERR(d))
> +		goto put_path;
> +
>  	dput(path->dentry);
>  	path->dentry = d;
>  
>  	if (test_share_config_flag(share_conf, KSMBD_SHARE_FLAG_CROSSMNT)) {
>  		err = follow_down(path, 0);
> -		if (err < 0) {
> -			path_put(path);
> -			return -ENOENT;
> -		}
> +		if (err < 0)
> +			goto put_path;
>  	}
>  	return 0;
> +
> +put_path:
> +	path_put(path);
> +	return -ENOENT;
>  }
>  
>  void ksmbd_vfs_query_maximal_access(struct mnt_idmap *idmap,
> -- 
> 2.51.0
> 
> 
>