From 3501ec357a73226d2b3c1bd204d97926f61b3eae Mon Sep 17 00:00:00 2001
From: Bob Liu <lliubbo@gmail.com>
Date: Wed, 11 Jul 2012 14:02:35 -0700
Subject: [PATCH] fs: ramfs: file-nommu: add SetPageUptodate()

commit fea9f718b3d68147f162ed2d870183ce5e0ad8d8 upstream.

There is a bug in the below scenario for !CONFIG_MMU:

 1. create a new file
 2. mmap the file and write to it
 3. read the file can't get the correct value

Because

  sys_read() -> generic_file_aio_read() -> simple_readpage() -> clear_page()

which causes the page to be zeroed.

Add SetPageUptodate() to ramfs_nommu_expand_for_mapping() so that
generic_file_aio_read() do not call simple_readpage().

Signed-off-by: Bob Liu <lliubbo@gmail.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Greg Ungerer <gerg@uclinux.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 fs/ramfs/file-nommu.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/ramfs/file-nommu.c b/fs/ramfs/file-nommu.c
index fbb0b478a346..d5378d028589 100644
--- a/fs/ramfs/file-nommu.c
+++ b/fs/ramfs/file-nommu.c
@@ -110,6 +110,7 @@ int ramfs_nommu_expand_for_mapping(struct inode *inode, size_t newsize)
 
 		/* prevent the page from being discarded on memory pressure */
 		SetPageDirty(page);
+		SetPageUptodate(page);
 
 		unlock_page(page);
 		put_page(page);
-- 
2.39.2