[patch] error handling of ERR_PTR() returns

[patch] error handling of ERR_PTR() returns

[Dan Carpenter]

There are a couple functions which return ERR_PTR as well as NULL.  The 
caller needs to handle both.

Smatch also complains about the handling of alloc_extent_map() but as far 
as I can see that doesn't actually return an ERR_PTR.

Compile tested on 2.6.29.

regards,
dan carpenter

--- orig/fs/btrfs/disk-io.c	2009-04-07 16:15:36.000000000 +0300
+++ devel/fs/btrfs/disk-io.c	2009-04-07 16:23:33.000000000 +0300
@@ -123,7 +123,7 @@
 
 	spin_lock(&em_tree->lock);
 	em = lookup_extent_mapping(em_tree, start, len);
-	if (em) {
+	if (!IS_ERR(em) && em) {
 		em->bdev =
 			BTRFS_I(inode)->root->fs_info->fs_devices->latest_bdev;
 		spin_unlock(&em_tree->lock);
@@ -1216,8 +1216,8 @@
 	int ret;
 
 	root = btrfs_read_fs_root_no_name(fs_info, location);
-	if (!root)
-		return NULL;
+	if (!root || IS_ERR(root))
+		return root;
 
 	if (root->in_sysfs)
 		return root;
@@ -1324,7 +1324,7 @@
 	spin_lock(&em_tree->lock);
 	em = lookup_extent_mapping(em_tree, offset, PAGE_CACHE_SIZE);
 	spin_unlock(&em_tree->lock);
-	if (!em) {
+	if (!em || IS_ERR(em)) {
 		__unplug_io_fn(bdi, page);
 		return;
 	}

Re: [patch] error handling of ERR_PTR() returns

[Andrey Kuzmin]

Since both NULL ptr and IS_ERR(ptr) are treated as error, why not
redefine IS_ERR to handle both, simplifying caller's life?

Regards,
Andrey



On Tue, Apr 7, 2009 at 5:38 PM, Dan Carpenter <error27@gmail.com> wrote=
:
> There are a couple functions which return ERR_PTR as well as NULL. =C2=
=A0The
> caller needs to handle both.
>
> Smatch also complains about the handling of alloc_extent_map() but as=
 far
> as I can see that doesn't actually return an ERR_PTR.
>
> Compile tested on 2.6.29.
>
> regards,
> dan carpenter
>
> --- orig/fs/btrfs/disk-io.c =C2=A0 =C2=A0 2009-04-07 16:15:36.0000000=
00 +0300
> +++ devel/fs/btrfs/disk-io.c =C2=A0 =C2=A02009-04-07 16:23:33.0000000=
00 +0300
> @@ -123,7 +123,7 @@
>
> =C2=A0 =C2=A0 =C2=A0 =C2=A0spin_lock(&em_tree->lock);
> =C2=A0 =C2=A0 =C2=A0 =C2=A0em =3D lookup_extent_mapping(em_tree, star=
t, len);
> - =C2=A0 =C2=A0 =C2=A0 if (em) {
> + =C2=A0 =C2=A0 =C2=A0 if (!IS_ERR(em) && em) {
> =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0em->bdev =3D
> =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0=
 =C2=A0 =C2=A0BTRFS_I(inode)->root->fs_info->fs_devices->latest_bdev;
> =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0spin_unlock(&e=
m_tree->lock);
> @@ -1216,8 +1216,8 @@
> =C2=A0 =C2=A0 =C2=A0 =C2=A0int ret;
>
> =C2=A0 =C2=A0 =C2=A0 =C2=A0root =3D btrfs_read_fs_root_no_name(fs_inf=
o, location);
> - =C2=A0 =C2=A0 =C2=A0 if (!root)
> - =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 return NULL;
> + =C2=A0 =C2=A0 =C2=A0 if (!root || IS_ERR(root))
> + =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 return root;
>
> =C2=A0 =C2=A0 =C2=A0 =C2=A0if (root->in_sysfs)
> =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0return root;
> @@ -1324,7 +1324,7 @@
> =C2=A0 =C2=A0 =C2=A0 =C2=A0spin_lock(&em_tree->lock);
> =C2=A0 =C2=A0 =C2=A0 =C2=A0em =3D lookup_extent_mapping(em_tree, offs=
et, PAGE_CACHE_SIZE);
> =C2=A0 =C2=A0 =C2=A0 =C2=A0spin_unlock(&em_tree->lock);
> - =C2=A0 =C2=A0 =C2=A0 if (!em) {
> + =C2=A0 =C2=A0 =C2=A0 if (!em || IS_ERR(em)) {
> =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0__unplug_io_fn=
(bdi, page);
> =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0return;
> =C2=A0 =C2=A0 =C2=A0 =C2=A0}
> --
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ml
>
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Re: [patch] error handling of ERR_PTR() returns

[Jeff Mahoney]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Andrey Kuzmin wrote:
> Since both NULL ptr and IS_ERR(ptr) are treated as error, why not
> redefine IS_ERR to handle both, simplifying caller's life?

IS_ERR is a global kernel function, and NULL isn't always an error.

- -Jeff

> On Tue, Apr 7, 2009 at 5:38 PM, Dan Carpenter <error27@gmail.com> wrote:
>> There are a couple functions which return ERR_PTR as well as NULL.  The
>> caller needs to handle both.
>>
>> Smatch also complains about the handling of alloc_extent_map() but as far
>> as I can see that doesn't actually return an ERR_PTR.
>>
>> Compile tested on 2.6.29.
>>
>> regards,
>> dan carpenter
>>
>> --- orig/fs/btrfs/disk-io.c     2009-04-07 16:15:36.000000000 +0300
>> +++ devel/fs/btrfs/disk-io.c    2009-04-07 16:23:33.000000000 +0300
>> @@ -123,7 +123,7 @@
>>
>>        spin_lock(&em_tree->lock);
>>        em = lookup_extent_mapping(em_tree, start, len);
>> -       if (em) {
>> +       if (!IS_ERR(em) && em) {
>>                em->bdev =
>>                        BTRFS_I(inode)->root->fs_info->fs_devices->latest_bdev;
>>                spin_unlock(&em_tree->lock);
>> @@ -1216,8 +1216,8 @@
>>        int ret;
>>
>>        root = btrfs_read_fs_root_no_name(fs_info, location);
>> -       if (!root)
>> -               return NULL;
>> +       if (!root || IS_ERR(root))
>> +               return root;
>>
>>        if (root->in_sysfs)
>>                return root;
>> @@ -1324,7 +1324,7 @@
>>        spin_lock(&em_tree->lock);
>>        em = lookup_extent_mapping(em_tree, offset, PAGE_CACHE_SIZE);
>>        spin_unlock(&em_tree->lock);
>> -       if (!em) {
>> +       if (!em || IS_ERR(em)) {
>>                __unplug_io_fn(bdi, page);
>>                return;
>>        }
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>
> --
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> the body of a message to majordomo@vger.kernel.org
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- --
Jeff Mahoney
SUSE Labs
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