linux-kernel - [PATCH 1/5] f2fs: fix race in between GC and atomic open

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Date:   Wed, 18 Apr 2018 17:45:01 +0800
From:   Chao Yu <yuchao0@...wei.com>
To:     <jaegeuk@...nel.org>
CC:     <linux-f2fs-devel@...ts.sourceforge.net>,
        <linux-kernel@...r.kernel.org>, <chao@...nel.org>,
        Chao Yu <yuchao0@...wei.com>
Subject: [PATCH 1/5] f2fs: fix race in between GC and atomic open

Thread					GC thread
- f2fs_ioc_start_atomic_write
 - get_dirty_pages
 - filemap_write_and_wait_range
					- f2fs_gc
					 - do_garbage_collect
					  - gc_data_segment
					   - move_data_page
					    - f2fs_is_atomic_file
					    - set_page_dirty
 - set_inode_flag(, FI_ATOMIC_FILE)

Dirty data page can still be generated by GC in race condition as
above call stack.

This patch adds fi->dio_rwsem[WRITE] in f2fs_ioc_start_atomic_write
to avoid such race.

Signed-off-by: Chao Yu <yuchao0@...wei.com>
---
 fs/f2fs/file.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 78b3a58cfe21..408471bf4799 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -1677,6 +1677,8 @@ static int f2fs_ioc_start_atomic_write(struct file *filp)
 
 	inode_lock(inode);
 
+	down_write(&F2FS_I(inode)->dio_rwsem[WRITE]);
+
 	if (f2fs_is_atomic_file(inode))
 		goto out;
 
@@ -1702,6 +1704,7 @@ static int f2fs_ioc_start_atomic_write(struct file *filp)
 	stat_inc_atomic_write(inode);
 	stat_update_max_atomic_write(inode);
 out:
+	up_write(&F2FS_I(inode)->dio_rwsem[WRITE]);
 	inode_unlock(inode);
 	mnt_drop_write_file(filp);
 	return ret;
-- 
2.15.0.55.gc2ece9dc4de6