linux-kernel - Re: [PATCH] btrfs: Fix passing 0 to ERR_PTR in btrfs_search_dir_index

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Message-ID: <01b2539f-6560-baa2-d968-5675f0ff2815@huawei.com>
Date: Tue, 22 Oct 2024 11:22:40 +0800
From: Yue Haibing <yuehaibing@...wei.com>
To: Johannes Thumshirn <Johannes.Thumshirn@....com>, "clm@...com"
	<clm@...com>, "josef@...icpanda.com" <josef@...icpanda.com>,
	"dsterba@...e.com" <dsterba@...e.com>, "mpdesouza@...e.com"
	<mpdesouza@...e.com>, "gniebler@...e.com" <gniebler@...e.com>
CC: "linux-btrfs@...r.kernel.org" <linux-btrfs@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] btrfs: Fix passing 0 to ERR_PTR in
 btrfs_search_dir_index_item()

On 2024/10/21 16:25, Johannes Thumshirn wrote:
> On 19.10.24 11:07, Yue Haibing wrote:
>> Return NULL instead of passing to ERR_PTR while ret is zero, this fix
>> smatch warnings:
>>
>> fs/btrfs/dir-item.c:353
>>   btrfs_search_dir_index_item() warn: passing zero to 'ERR_PTR'
>>
>> Fixes: 9dcbe16fccbb ("btrfs: use btrfs_for_each_slot in btrfs_search_dir_index_item")
>> Signed-off-by: Yue Haibing <yuehaibing@...wei.com>
>> ---
>>   fs/btrfs/dir-item.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/fs/btrfs/dir-item.c b/fs/btrfs/dir-item.c
>> index 001c0c2f872c..cdb30ec7366a 100644
>> --- a/fs/btrfs/dir-item.c
>> +++ b/fs/btrfs/dir-item.c
>> @@ -350,7 +350,7 @@ btrfs_search_dir_index_item(struct btrfs_root *root, struct btrfs_path *path,
>>   	if (ret > 0)
>>   		ret = 0;
>>   
>> -	return ERR_PTR(ret);
>> +	return ret ? ERR_PTR(ret) : NULL;
>>   }
>>   
>>   struct btrfs_dir_item *btrfs_lookup_xattr(struct btrfs_trans_handle *trans,
> 
> The only caller to this is in btrfs_unlink_subvol(), which does the 
> following:
> 
> 
>                   di = btrfs_search_dir_index_item(root, path, dir_ino,
> 						  &fname.disk_name);
>                   if (IS_ERR_OR_NULL(di)) {
>                           if (!di)
>                                   ret = -ENOENT;
>                           else
>                                   ret = PTR_ERR(di);
>                           btrfs_abort_transaction(trans, ret);
>                           goto out;
>                   }
> 
> to do:
> 
> diff --git a/fs/btrfs/dir-item.c b/fs/btrfs/dir-item.c
> index d3093eba54a5..e755228d909a 100644
> --- a/fs/btrfs/dir-item.c
> +++ b/fs/btrfs/dir-item.c
> @@ -345,10 +345,7 @@ btrfs_search_dir_index_item(struct btrfs_root 
> *root, struct btrfs_path *path,
>                          return di;
>          }
>          /* Adjust return code if the key was not found in the next leaf. */


ret is output variable of btrfs_for_each_slot, that return value can be 0, if a
valid slot was found, 1 if there were no more leaves, and < 0 if there was an
error.

> -       if (ret > 0)
> -               ret = 0;
> -
> -       return ERR_PTR(ret);
> +       return ERR_PTR(-ENOENT);

This overwrite other ret code, which expecting return to upstream caller

>   }
> 
>   struct btrfs_dir_item *btrfs_lookup_xattr(struct btrfs_trans_handle 
> *trans,
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index 35f89d14c110..00602634db3a 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -4337,11 +4337,8 @@ static int btrfs_unlink_subvol(struct 
> btrfs_trans_handle *trans,
>           */
>          if (btrfs_ino(inode) == BTRFS_EMPTY_SUBVOL_DIR_OBJECTID) {
>                  di = btrfs_search_dir_index_item(root, path, dir_ino, 
> &fname.disk_name);
> -               if (IS_ERR_OR_NULL(di)) {
> -                       if (!di)
> -                               ret = -ENOENT;
> -                       else
> -                               ret = PTR_ERR(di);
> +               if (IS_ERR(di)) {
> +                       ret = PTR_ERR(di);
>                          btrfs_abort_transaction(trans, ret);
>                          goto out;
>                  }
> This is completely untested though and needs to be re-checked if it's 
> even correct.