On Fri, 16 May 2014 10:42:29 +0800 Tang Chen <tangchen@xxxxxxxxxxxxxx> wrote:
> We use the following command to online a memory_block:
>
> echo online|online_kernel|online_movable > /sys/devices/system/memory/memoryXXX/state
>
> But, if we typed "online_movbale" by mistake (typo, not "online_movable"), it will be
> recognized as "online", and it will online the memory block successfully. "online" command
> will put the memory block into the same zone as it was in before last offlined, which may
> be ZONE_NORMAL, not ZONE_MOVABLE. Since it succeeds without any warning, it may confuse
> users.
>
> ...
>
> --- a/drivers/base/memory.c
> +++ b/drivers/base/memory.c
> @@ -319,19 +319,27 @@ store_mem_state(struct device *dev,
> struct device_attribute *attr, const char *buf, size_t count)
> {
> struct memory_block *mem = to_memory_block(dev);
> - int ret, online_type;
> + int ret, online_type, len;
>
> ret = lock_device_hotplug_sysfs();
> if (ret)
> return ret;
>
> - if (!strncmp(buf, "online_kernel", min_t(int, count, 13)))
> + /*
> + * count passed from user space includes \0, so the real length
> + * is count-1.
> + */
> + len = count - 1;
> +
> + if (len == strlen("online_kernel") &&
> + !strncmp(buf, "online_kernel", len))
> online_type = ONLINE_KERNEL;
> - else if (!strncmp(buf, "online_movable", min_t(int, count, 14)))
> + else if (len == strlen("online_movable") &&
> + !strncmp(buf, "online_movable", len))
> online_type = ONLINE_MOVABLE;
> - else if (!strncmp(buf, "online", min_t(int, count, 6)))
> + else if (len == strlen("online") && !strncmp(buf, "online", len))
> online_type = ONLINE_KEEP;
> - else if (!strncmp(buf, "offline", min_t(int, count, 7)))
> + else if (len == strlen("offline") && !strncmp(buf, "offline", len))
> online_type = -1;
> else {
> ret = -EINVAL;
hm, why is this code so complicated? Is it because it is trying not to
trip over possibly-absent trailing newline? If so, please take a look
at sysfs_streq().
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