On Thu, May 03, 2007 at 11:14:50PM -0700, Andrew Morton wrote:
>On Sat, 28 Apr 2007 13:30:23 +0800 WANG Cong <[email protected]> wrote:
>
>> Since 'sysfs_create_file' is declared with attribute warn_unused_result, we must always check its return value carefully.
>>
>
>Well that's not really the reason for your patch.
>
>warn_unused_result is there to tell us that there are deeper problems in
>the code which need addressing: the failure to check the
>sysfs_create_file() return value means that bugs in the kernel can remain
>undetected, or can be harder to find.
Oh, thanks very much for your pointing.
>
>>
>> ---
>>
>> --- linux-2.6.21-rc7-mm2/drivers/block/nbd.c.orig 2007-04-27 17:27:47.000000000 +0800
>> +++ linux-2.6.21-rc7-mm2/drivers/block/nbd.c 2007-04-27 17:47:32.000000000 +0800
>> @@ -373,7 +373,10 @@ static void nbd_do_it(struct nbd_device
>> BUG_ON(lo->magic != LO_MAGIC);
>>
>> lo->pid = current->pid;
>> - sysfs_create_file(&lo->disk->kobj, &pid_attr.attr);
>> + if (sysfs_create_file(&lo->disk->kobj, &pid_attr.attr)) {
>> + printk(KERN_ERR "nbd: sysfs_create_file failed!");
>> + return;
>> + }
>>
>> while ((req = nbd_read_stat(lo)) != NULL)
>> nbd_end_request(req);
>
>It would better saner to propagate this error back through callers:
>
>--- a/drivers/block/nbd.c~nbd-check-the-return-value-of-sysfs_create_file-fix
>+++ a/drivers/block/nbd.c
>@@ -366,23 +366,25 @@ static struct disk_attribute pid_attr =
> .show = pid_show,
> };
>
>-static void nbd_do_it(struct nbd_device *lo)
>+static int nbd_do_it(struct nbd_device *lo)
> {
> struct request *req;
>+ int ret;
>
> BUG_ON(lo->magic != LO_MAGIC);
>
> lo->pid = current->pid;
>- if (sysfs_create_file(&lo->disk->kobj, &pid_attr.attr)) {
>+ ret = sysfs_create_file(&lo->disk->kobj, &pid_attr.attr);
>+ if (ret) {
> printk(KERN_ERR "nbd: sysfs_create_file failed!");
>- return;
>+ return ret;
> }
>
> while ((req = nbd_read_stat(lo)) != NULL)
> nbd_end_request(req);
>
> sysfs_remove_file(&lo->disk->kobj, &pid_attr.attr);
>- return;
>+ return 0;
> }
>
> static void nbd_clear_que(struct nbd_device *lo)
>@@ -572,7 +574,9 @@ static int nbd_ioctl(struct inode *inode
> case NBD_DO_IT:
> if (!lo->file)
> return -EINVAL;
>- nbd_do_it(lo);
>+ error = nbd_do_it(lo);
>+ if (error)
>+ return error;
> /* on return tidy up in case we have a signal */
> /* Forcibly shutdown the socket causing all listeners
> * to error
>_
Well, better code. ;) I didn't consider changing the type of nbd_do_it().
Thanks again!
-
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