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

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Message-ID: <7daf798c-64e1-4d22-9840-8954db354c9a@wdc.com>
Date: Mon, 21 Oct 2024 08:25:44 +0000
From: Johannes Thumshirn <Johannes.Thumshirn@....com>
To: Yue Haibing <yuehaibing@...wei.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 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. */
-       if (ret > 0)
-               ret = 0;
-
-       return ERR_PTR(ret);
+       return ERR_PTR(-ENOENT);
  }

  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.