linux-kernel - [GFS2] Patch to fix mmap of stuffed files [31/34]

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Date:	Tue, 01 May 2007 11:23:33 +0100
From:	Steven Whitehouse <swhiteho@...hat.com>
To:	cluster-devel@...hat.com
Cc:	linux-kernel@...r.kernel.org
Subject: [GFS2] Patch to fix mmap of stuffed files [31/34]

>>From bf126aee6d54fe1e509846abf3b27aba84c6d7ce Mon Sep 17 00:00:00 2001
From: Steven Whitehouse <swhiteho@...hat.com>
Date: Fri, 20 Apr 2007 09:18:30 +0100
Subject: [PATCH] [GFS2] Patch to fix mmap of stuffed files

If a stuffed file is mmaped and a page fault is generated at some offset
above the initial page, we need to create a zero page to hang the buffer
heads off before we can unstuff the file. This is a fix for bz #236087

Signed-off-by: Steven Whitehouse <swhiteho@...hat.com>

diff --git a/fs/gfs2/ops_address.c b/fs/gfs2/ops_address.c
index 90c2879..30c1562 100644
--- a/fs/gfs2/ops_address.c
+++ b/fs/gfs2/ops_address.c
@@ -197,7 +197,19 @@ static int stuffed_readpage(struct gfs2_inode *ip, struct page *page)
 	void *kaddr;
 	int error;
 
-	BUG_ON(page->index);
+	/*
+	 * Due to the order of unstuffing files and ->nopage(), we can be
+	 * asked for a zero page in the case of a stuffed file being extended,
+	 * so we need to supply one here. It doesn't happen often.
+	 */
+	if (unlikely(page->index)) {
+		kaddr = kmap_atomic(page, KM_USER0);
+		memset(kaddr, 0, PAGE_CACHE_SIZE);
+		kunmap_atomic(kaddr, KM_USER0);
+		flush_dcache_page(page);
+		SetPageUptodate(page);
+		return 0;
+	}
 
 	error = gfs2_meta_inode_buffer(ip, &dibh);
 	if (error)
@@ -208,9 +220,8 @@ static int stuffed_readpage(struct gfs2_inode *ip, struct page *page)
 	       ip->i_di.di_size);
 	memset(kaddr + ip->i_di.di_size, 0, PAGE_CACHE_SIZE - ip->i_di.di_size);
 	kunmap_atomic(kaddr, KM_USER0);
-
+	flush_dcache_page(page);
 	brelse(dibh);
-
 	SetPageUptodate(page);
 
 	return 0;
-- 
1.5.1.2



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