Messages in this thread | | | Date | Thu, 1 Mar 2012 12:15:57 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH] mm: extend prefault helpers to fault in more than PAGE_SIZE |
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On Thu, 1 Mar 2012 20:22:59 +0100 Daniel Vetter <daniel.vetter@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.
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