fs: convert core functions to zero_user_page

It's very common for file systems to need to zero part or all of a page,
the simplist way is just to use kmap_atomic() and memset().  There's
actually a library function in include/linux/highmem.h that does exactly
that, but it's confusingly named memclear_highpage_flush(), which is
descriptive of *how* it does the work rather than what the *purpose* is.
So this patchset renames the function to zero_user_page(), and calls it
from the various places that currently open code it.

This first patch introduces the new function call, and converts all the
core kernel callsites, both the open-coded ones and the old
memclear_highpage_flush() ones.  Following this patch is a series of
conversions for each file system individually, per AKPM, and finally a
patch deprecating the old call.  The diffstat below shows the entire
patchset.

[akpm@linux-foundation.org: fix a few things]
Signed-off-by: Nate Diller <nate.diller@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 5 insertions, 10 deletions

diff --git a/fs/mpage.c b/fs/mpage.c
index fa2441f57b41..0fb914fc2ee0 100644
--- a/fs/mpage.c
+++ b/fs/mpage.c
@@ -284,11 +284,9 @@ do_mpage_readpage(struct bio *bio, struct page *page, unsigned nr_pages,
         }
 
         if (first_hole != blocks_per_page) {
-                char *kaddr = kmap_atomic(page, KM_USER0);
-                memset(kaddr + (first_hole << blkbits), 0,
-                                PAGE_CACHE_SIZE - (first_hole << blkbits));
-                flush_dcache_page(page);
-                kunmap_atomic(kaddr, KM_USER0);
+                zero_user_page(page, first_hole << blkbits,
+                                PAGE_CACHE_SIZE - (first_hole << blkbits),
+                                KM_USER0);
                 if (first_hole == 0) {
                         SetPageUptodate(page);
                         unlock_page(page);
@@ -576,14 +574,11 @@ page_is_mapped:
                  * written out to the file."
                  */
                 unsigned offset = i_size & (PAGE_CACHE_SIZE - 1);
-                char *kaddr;
 
                 if (page->index > end_index || !offset)
                         goto confused;
-                kaddr = kmap_atomic(page, KM_USER0);
-                memset(kaddr + offset, 0, PAGE_CACHE_SIZE - offset);
-                flush_dcache_page(page);
-                kunmap_atomic(kaddr, KM_USER0);
+                zero_user_page(page, offset, PAGE_CACHE_SIZE - offset,
+                                KM_USER0);
         }
 
         /*