[Ocfs2-devel] [PATCH 05/15] ocfs2: return 0 in page_mkwrite to let VFS retry.

[Sunil Mushran]

From: Tao Ma <tao.ma at oracle.com>

Mainline commit 4c1bbf1ba631d7db61ce3462349a3f5d14ae3009

In ocfs2_page_mkwrite, we return -EINVAL when we found the page mapping
isn't updated, and it will cause the user space program get SIGBUS and
exit. The reason is that during race writeable mmap, we will do
unmap_mapping_range in ocfs2_data_downconvert_worker. The good thing is
that if we reuturn 0 in page_mkwrite, VFS will retry fault and then
call page_mkwrite again, so it is safe to return 0 here.

Signed-off-by: Tao Ma <tao.ma at oracle.com>
Signed-off-by: Mark Fasheh <mfasheh at suse.com>
---
 fs/ocfs2/mmap.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/fs/ocfs2/mmap.c b/fs/ocfs2/mmap.c
index ff5dc1d..4a07c4a 100644
--- a/fs/ocfs2/mmap.c
+++ b/fs/ocfs2/mmap.c
@@ -147,7 +147,11 @@ static int __ocfs2_page_mkwrite(struct inode *inode, struct buffer_head *di_bh,
 	 * ocfs2_write_begin_nolock().
 	 */
 	if (!PageUptodate(page) || page->mapping != inode->i_mapping) {
-		ret = -EINVAL;
+		/*
+		 * the page has been umapped in ocfs2_data_downconvert_worker.
+		 * So return 0 here and let VFS retry.
+		 */
+		ret = 0;
 		goto out;
 	}
 
-- 
1.5.6.3