On Wed, 7 Nov 2012 03:01:28 -0800
Anton Vorontsov <anton.vorontsov@xxxxxxxxxx> wrote:
> This patch introduces vmpressure_fd() system call. The system call creates
> a new file descriptor that can be used to monitor Linux' virtual memory
> management pressure.
I noticed a couple of quick things as I was looking this over...
> +static ssize_t vmpressure_read(struct file *file, char __user *buf,
> + size_t count, loff_t *ppos)
> +{
> + struct vmpressure_watch *watch = file->private_data;
> + struct vmpressure_event event;
> + int ret;
> +
> + if (count < sizeof(event))
> + return -EINVAL;
> +
> + ret = wait_event_interruptible(watch->waitq,
> + atomic_read(&watch->pending));
Would it make sense to support non-blocking reads? Perhaps a process would
like to simply know that current pressure level?
> +SYSCALL_DEFINE1(vmpressure_fd, struct vmpressure_config __user *, config)
> +{
> + struct vmpressure_watch *watch;
> + struct file *file;
> + int ret;
> + int fd;
> +
> + watch = kzalloc(sizeof(*watch), GFP_KERNEL);
> + if (!watch)
> + return -ENOMEM;
> +
> + ret = copy_from_user(&watch->config, config, sizeof(*config));
> + if (ret)
> + goto err_free;
This is wrong - you'll return the number of uncopied bytes to user space.
You'll need a "ret = -EFAULT;" in there somewhere.
jon
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