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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Chao Yu <yuchao0@huawei.com>,
        Jaegeuk Kim <jaegeuk@kernel.org>
Subject: [PATCH 4.20 39/52] f2fs: wait on atomic writes to count F2FS_CP_WB_DATA
Date:   Mon, 18 Mar 2019 10:25:26 +0100
Message-Id: <20190318083847.881394513@linuxfoundation.org>
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4.20-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jaegeuk Kim <jaegeuk@kernel.org>

commit 31867b23d7d1ee3535136c6a410a6cf56f666bfc upstream.

Otherwise, we can get wrong counts incurring checkpoint hang.

IO_W (CP:  -24, Data:   24, Flush: (   0    0    1), Discard: (   0    0))

Thread A                        Thread B
- f2fs_write_data_pages
 -  __write_data_page
  - f2fs_submit_page_write
   - inc_page_count(F2FS_WB_DATA)
     type is F2FS_WB_DATA due to file is non-atomic one
- f2fs_ioc_start_atomic_write
 - set_inode_flag(FI_ATOMIC_FILE)
                                - f2fs_write_end_io
                                 - dec_page_count(F2FS_WB_CP_DATA)
                                   type is F2FS_WB_DATA due to file becomes
                                   atomic one

Cc: <stable@vger.kernel.org>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/f2fs/file.c |   12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -1749,10 +1749,12 @@ static int f2fs_ioc_start_atomic_write(s
 
 	down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
 
-	if (!get_dirty_pages(inode))
-		goto skip_flush;
-
-	f2fs_msg(F2FS_I_SB(inode)->sb, KERN_WARNING,
+	/*
+	 * Should wait end_io to count F2FS_WB_CP_DATA correctly by
+	 * f2fs_is_atomic_file.
+	 */
+	if (get_dirty_pages(inode))
+		f2fs_msg(F2FS_I_SB(inode)->sb, KERN_WARNING,
 		"Unexpected flush for atomic writes: ino=%lu, npages=%u",
 					inode->i_ino, get_dirty_pages(inode));
 	ret = filemap_write_and_wait_range(inode->i_mapping, 0, LLONG_MAX);
@@ -1760,7 +1762,7 @@ static int f2fs_ioc_start_atomic_write(s
 		up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
 		goto out;
 	}
-skip_flush:
+
 	set_inode_flag(inode, FI_ATOMIC_FILE);
 	clear_inode_flag(inode, FI_ATOMIC_REVOKE_REQUEST);
 	up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);