exfat: flush dirty metadata in fsync

generic_file_fsync() exfat used could not guarantee the consistency of
a file because it has flushed not dirty metadata but only dirty data pages
for a file.

Instead of that, use exfat_file_fsync() for files and directories so that
it guarantees to commit both the metadata and data pages for a file.
Signed-off-by: Sungjong Seo <sj1557.seo@samsung.com>
Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>

fs/exfat/dir.c

@@ -309,7 +309,7 @@ const struct file_operations exfat_dir_operations = {
 	.llseek		= generic_file_llseek,
 	.read		= generic_read_dir,
 	.iterate	= exfat_iterate,
-	.fsync		= generic_file_fsync,
+	.fsync		= exfat_file_fsync,
 };
 
 int exfat_alloc_new_dir(struct inode *inode, struct exfat_chain *clu)

fs/exfat/exfat_fs.h

@@ -420,6 +420,7 @@ void exfat_truncate(struct inode *inode, loff_t size);
 int exfat_setattr(struct dentry *dentry, struct iattr *attr);
 int exfat_getattr(const struct path *path, struct kstat *stat,
 		unsigned int request_mask, unsigned int query_flags);
+int exfat_file_fsync(struct file *file, loff_t start, loff_t end, int datasync);
 
 /* namei.c */
 extern const struct dentry_operations exfat_dentry_ops;

fs/exfat/file.c

@@ -6,6 +6,7 @@
 #include <linux/slab.h>
 #include <linux/cred.h>
 #include <linux/buffer_head.h>
+#include <linux/blkdev.h>
 
 #include "exfat_raw.h"
 #include "exfat_fs.h"
@@ -346,12 +347,28 @@ int exfat_setattr(struct dentry *dentry, struct iattr *attr)
 	return error;
 }
 
+int exfat_file_fsync(struct file *filp, loff_t start, loff_t end, int datasync)
+{
+	struct inode *inode = filp->f_mapping->host;
+	int err;
+
+	err = __generic_file_fsync(filp, start, end, datasync);
+	if (err)
+		return err;
+
+	err = sync_blockdev(inode->i_sb->s_bdev);
+	if (err)
+		return err;
+
+	return blkdev_issue_flush(inode->i_sb->s_bdev, GFP_KERNEL);
+}
+
 const struct file_operations exfat_file_operations = {
 	.llseek		= generic_file_llseek,
 	.read_iter	= generic_file_read_iter,
 	.write_iter	= generic_file_write_iter,
 	.mmap		= generic_file_mmap,
-	.fsync		= generic_file_fsync,
+	.fsync		= exfat_file_fsync,
 	.splice_read	= generic_file_splice_read,
 	.splice_write	= iter_file_splice_write,
 };