On Thu, 1 Mar 2012 20:22:59 +0100
Daniel Vetter <daniel.vetter at ffwll.ch> wrote:
> drm/i915 wants to read/write more than one page in its fastpath
> and hence needs to prefault more than PAGE_SIZE bytes.
>
> Add new functions in filemap.h to make that possible.
>
> Also kill a copy&pasted spurious space in both functions while at it.
>
>
> ...
>
> +/* Multipage variants of the above prefault helpers, useful if more than
> + * PAGE_SIZE of date needs to be prefaulted. These are separate from the above
> + * functions (which only handle up to PAGE_SIZE) to avoid clobbering the
> + * filemap.c hotpaths. */
Like this please:
/*
* Multipage variants of the above prefault helpers, useful if more than
* PAGE_SIZE of date needs to be prefaulted. These are separate from the above
* functions (which only handle up to PAGE_SIZE) to avoid clobbering the
* filemap.c hotpaths.
*/
and s/date/data/
> +static inline int fault_in_multipages_writeable(char __user *uaddr, int size)
> +{
> + int ret;
> + const char __user *end = uaddr + size - 1;
> +
> + if (unlikely(size == 0))
> + return 0;
> +
> + /*
> + * Writing zeroes into userspace here is OK, because we know that if
> + * the zero gets there, we'll be overwriting it.
> + */
Yeah, like that.
> + while (uaddr <= end) {
> + ret = __put_user(0, uaddr);
> + if (ret != 0)
> + return ret;
> + uaddr += PAGE_SIZE;
> + }
> +
> + /* Check whether the range spilled into the next page. */
> + if (((unsigned long)uaddr & PAGE_MASK) ==
> + ((unsigned long)end & PAGE_MASK))
> + ret = __put_user(0, end);
> +
> + return ret;
> +}
> +
> +static inline int fault_in_multipages_readable(const char __user *uaddr,
> + int size)
> +{
> + volatile char c;
> + int ret;
> + const char __user *end = uaddr + size - 1;
> +
> + if (unlikely(size == 0))
> + return 0;
> +
> + while (uaddr <= end) {
> + ret = __get_user(c, uaddr);
> + if (ret != 0)
> + return ret;
> + uaddr += PAGE_SIZE;
> + }
> +
> + /* Check whether the range spilled into the next page. */
> + if (((unsigned long)uaddr & PAGE_MASK) ==
> + ((unsigned long)end & PAGE_MASK)) {
> + ret = __get_user(c, end);
> + (void)c;
> + }
> +
> + return ret;
> +}
Please merge it via the DRI tree.
