mm: write iovec cleanup

Hide some of the open-coded nr_segs tests into the iovec helpers.  This is all
to simplify generic_file_buffered_write, because that gets more complex in the
next patch.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 7 insertions, 10 deletions

diff --git a/mm/filemap_xip.c b/mm/filemap_xip.c
index 53ee6a299635..32132f3cd641 100644
--- a/mm/filemap_xip.c
+++ b/mm/filemap_xip.c
@@ -15,7 +15,6 @@
 #include <linux/rmap.h>
 #include <linux/sched.h>
 #include <asm/tlbflush.h>
-#include "filemap.h"
 
 /*
  * We do use our own empty page to avoid interference with other users
@@ -288,6 +287,7 @@ __xip_file_write(struct file *filp, const char __user *buf,
                 unsigned long index;
                 unsigned long offset;
                 size_t copied;
+                char *kaddr;
 
                 offset = (pos & (PAGE_CACHE_SIZE -1)); /* Within page */
                 index = pos >> PAGE_CACHE_SHIFT;
@@ -295,14 +295,6 @@ __xip_file_write(struct file *filp, const char __user *buf,
                 if (bytes > count)
                         bytes = count;
 
-                /*
-                 * Bring in the user page that we will copy from _first_.
-                 * Otherwise there's a nasty deadlock on copying from the
-                 * same page as we're writing to, without it being marked
-                 * up-to-date.
-                 */
-                fault_in_pages_readable(buf, bytes);
-
                 page = a_ops->get_xip_page(mapping,
                                            index*(PAGE_SIZE/512), 0);
                 if (IS_ERR(page) && (PTR_ERR(page) == -ENODATA)) {
@@ -319,8 +311,13 @@ __xip_file_write(struct file *filp, const char __user *buf,
                         break;
                 }
 
-                copied = filemap_copy_from_user(page, offset, buf, bytes);
+                fault_in_pages_readable(buf, bytes);
+                kaddr = kmap_atomic(page, KM_USER0);
+                copied = bytes -
+                        __copy_from_user_inatomic_nocache(kaddr, buf, bytes);
+                kunmap_atomic(kaddr, KM_USER0);
                 flush_dcache_page(page);
+
                 if (likely(copied > 0)) {
                         status = copied;