linux-ext4 - + ext4-use-simple_prepare_write-to-zero-page-data.patch added to -mm tree

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Date:	Mon, 09 Apr 2007 23:19:51 -0700
From:	akpm@...ux-foundation.org
To:	mm-commits@...r.kernel.org
Cc:	nate.diller@...il.com, linux-ext4@...r.kernel.org
Subject: + ext4-use-simple_prepare_write-to-zero-page-data.patch added to -mm tree


The patch titled
     ext4: use simple_prepare_write to zero page data
has been added to the -mm tree.  Its filename is
     ext4-use-simple_prepare_write-to-zero-page-data.patch

*** Remember to use Documentation/SubmitChecklist when testing your code ***

See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this

------------------------------------------------------
Subject: ext4: use simple_prepare_write to zero page data
From: Nate Diller <nate.diller@...il.com>

It's common for file systems to need to zero data on either side of a
write, if a page is not Uptodate during prepare_write.  It just so happens
that simple_prepare_write() in libfs.c does exactly that, so we can avoid
duplication and just call that function to zero page data.

Signed-off-by: Nate Diller <nate.diller@...il.com>
Cc: <linux-ext4@...r.kernel.org>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
---

 fs/ext4/writeback.c |   17 +----------------
 1 file changed, 1 insertion(+), 16 deletions(-)

diff -puN fs/ext4/writeback.c~ext4-use-simple_prepare_write-to-zero-page-data fs/ext4/writeback.c
--- a/fs/ext4/writeback.c~ext4-use-simple_prepare_write-to-zero-page-data
+++ a/fs/ext4/writeback.c
@@ -819,21 +819,6 @@ int ext4_wb_writepages(struct address_sp
 	return 0;
 }
 
-static void ext4_wb_clear_page(struct page *page, int from, int to)
-{
-	void *kaddr;
-
-	if (to < PAGE_CACHE_SIZE || from > 0) {
-		kaddr = kmap_atomic(page, KM_USER0);
-		if (PAGE_CACHE_SIZE > to)
-			memset(kaddr + to, 0, PAGE_CACHE_SIZE - to);
-		if (0 < from)
-			memset(kaddr, 0, from);
-		flush_dcache_page(page);
-		kunmap_atomic(kaddr, KM_USER0);
-	}
-}
-
 int ext4_wb_prepare_write(struct file *file, struct page *page,
 			      unsigned from, unsigned to)
 {
@@ -863,7 +848,7 @@ int ext4_wb_prepare_write(struct file *f
 			/* this block isn't allocated yet, reserve space */
 			wb_debug("reserve space for new block\n");
 			page->private = 1;
-			ext4_wb_clear_page(page, from, to);
+			simple_prepare_write(file, page, from, to);
 			ClearPageMappedToDisk(page);
 		} else { 
 			/* block is already mapped, so no need to reserve */
_

Patches currently in -mm which might be from nate.diller@...il.com are

cifs-use-simple_prepare_write-to-zero-page-data.patch
ext4-use-simple_prepare_write-to-zero-page-data.patch
reiser4-use-simple_prepare_write-to-zero-page-data.patch

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