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.
>
> ---
>
> --- 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
_
-
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