linux-kernel - [PATCH] fat: issue flush after the writeback of FAT

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Date:   Tue, 9 Apr 2019 11:01:58 +0800
From:   Hou Tao <houtao1@...wei.com>
To:     <hirofumi@...l.parknet.co.jp>
CC:     <linux-fsdevel@...r.kernel.org>, <viro@...iv.linux.org.uk>,
        <jack@...e.cz>, <linux-kernel@...r.kernel.org>
Subject: [PATCH] fat: issue flush after the writeback of FAT

fsync() needs to make sure the data & meta-data of file are persistent
after the return of fsync(), even when a power-failure occurs later.
In the case of fat-fs, the FAT belongs to the meta-data of file,
so we need to issue a flush after the writeback of FAT instead before.

Also bail out early when any stage of fsync fails.

Signed-off-by: Hou Tao <houtao1@...wei.com>
---
 fs/fat/file.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/fs/fat/file.c b/fs/fat/file.c
index b3bed32946b1..0e3ed79fcc3f 100644
--- a/fs/fat/file.c
+++ b/fs/fat/file.c
@@ -193,12 +193,17 @@ static int fat_file_release(struct inode *inode, struct file *filp)
 int fat_file_fsync(struct file *filp, loff_t start, loff_t end, int datasync)
 {
 	struct inode *inode = filp->f_mapping->host;
-	int res, err;
+	int err;
+
+	err = __generic_file_fsync(filp, start, end, datasync);
+	if (err)
+		return err;
 
-	res = generic_file_fsync(filp, start, end, datasync);
 	err = sync_mapping_buffers(MSDOS_SB(inode->i_sb)->fat_inode->i_mapping);
+	if (err)
+		return err;
 
-	return res ? res : err;
+	return blkdev_issue_flush(inode->i_sb->s_bdev, GFP_KERNEL, NULL);
 }
 
 
-- 
2.16.2.dirty