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authorDaniel Vetter <daniel.vetter@ffwll.ch>2012-03-25 19:47:41 +0200
committerDaniel Vetter <daniel.vetter@ffwll.ch>2012-03-27 13:36:30 +0200
commitf56f821feb7b36223f309e0ec05986bb137ce418 (patch)
tree5d6ae677300d4ea171bad39ba8f7aa65cf24c6d9 /include/linux/pagemap.h
parentd174bd6472d79fb5603dc8bd35e5184d83194ea8 (diff)
mm: extend prefault helpers to fault in more than PAGE_SIZE
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. v2: As suggested by Andrew Morton, add a multipage parameter to both functions to avoid the additional branch for the pagemap.c hotpath. My gcc 4.6 here seems to dtrt and indeed reap these branches where not needed. v3: Becaus I couldn't find a way around adding a uaddr += PAGE_SIZE to the filemap.c hotpaths (that the compiler couldn't remove again), let's go with separate new functions for the multipage use-case. v4: Adjust comment to CodingStlye and fix spelling. Acked-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Diffstat (limited to 'include/linux/pagemap.h')
-rw-r--r--include/linux/pagemap.h64
1 files changed, 62 insertions, 2 deletions
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index cfaaa6949b8b..c93a9a9bcd35 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -426,7 +426,7 @@ static inline int fault_in_pages_writeable(char __user *uaddr, int size)
*/
if (((unsigned long)uaddr & PAGE_MASK) !=
((unsigned long)end & PAGE_MASK))
- ret = __put_user(0, end);
+ ret = __put_user(0, end);
}
return ret;
}
@@ -445,13 +445,73 @@ static inline int fault_in_pages_readable(const char __user *uaddr, int size)
if (((unsigned long)uaddr & PAGE_MASK) !=
((unsigned long)end & PAGE_MASK)) {
- ret = __get_user(c, end);
+ ret = __get_user(c, end);
(void)c;
}
}
return ret;
}
+/*
+ * Multipage variants of the above prefault helpers, useful if more than
+ * PAGE_SIZE of data 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.
+ */
+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.
+ */
+ 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;
+}
+
int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
pgoff_t index, gfp_t gfp_mask);
int add_to_page_cache_lru(struct page *page, struct address_space *mapping,