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SubjectRe: [PATCH] To add NULL pointer check
From
Date
Hi,
Thank you for your contribution.

As I consider the null pointer check, generic_writepages() originally
does so.
Therefore, I think f2fs_write_data_pages() is better to handle this.
Please review the modified patch.
Thanks,

---
From d3c811a51c7062fb1b66bec910ed346447c02032 Mon Sep 17 00:00:00 2001
From: P J P <ppandit@redhat.com>
Date: Wed, 3 Apr 2013 11:38:00 +0900
Subject: [PATCH] f2fs: add NULL pointer check
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-f2fs-devel@lists.sourceforge.net

Commit - fa9150a84c - replaces a call to generic_writepages() in
f2fs_write_data_pages() with write_cache_pages(), with a function
pointer
argument pointing to routine: __f2fs_writepage.

->
https://git.kernel.org/linus/fa9150a84ca333f68127097c4fa1eda4b3913a22

This patch adds a NULL pointer check in f2fs_write_data_pages() to
avoid
a possible NULL pointer dereference, in case if -
mapping->a_ops->writepage -
is NULL.

Signed-off-by: P J P <ppandit@redhat.com>
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>
---
fs/f2fs/data.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 47a2d7c..cf9ff5f 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -559,6 +559,10 @@ static int f2fs_write_data_pages(struct
address_space *mapping,
int ret;
long excess_nrtw = 0, desired_nrtw;

+ /* deal with chardevs and other special file */
+ if (!mapping->a_ops->writepage)
+ return 0;
+
if (wbc->nr_to_write < MAX_DESIRED_PAGES_WP) {
desired_nrtw = MAX_DESIRED_PAGES_WP;
excess_nrtw = desired_nrtw - wbc->nr_to_write;
--
1.8.1.3.566.gaa39828


--
Jaegeuk Kim
Samsung
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