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

Steven Whitehouse
2007-05-01T10:28:11Z

>From bf126aee6d54fe1e509846abf3b27aba84c6d7ce Mon Sep 17 00:00:00 2001
From: Steven Whitehouse <swhiteho@redhat.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@redhat.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