ext2: Use generic_buffers_fsync() implementation

Next patch converts ext2 to use iomap interface for DIO.
iomap layer can call generic_write_sync() -> ext2_fsync() from
iomap_dio_complete while still holding the inode_lock().

Now writeback from other paths doesn't need inode_lock().
It seems there is also no need of an inode_lock() for
sync_mapping_buffers(). It uses it's own mapping->private_lock
for it's buffer list handling.
Hence this patch is in preparation to move ext2 to iomap.
This uses generic_buffers_fsync() which does not take any inode_lock()
in ext2_fsync().
Tested-by: Disha Goel <disgoel@linux.ibm.com>
Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Message-Id: <76d206a464574ff91db25bc9e43479b51ca7e307.1682069716.git.ritesh.list@gmail.com>

fs/ext2/file.c

@@ -25,6 +25,7 @@
 #include <linux/quotaops.h>
 #include <linux/iomap.h>
 #include <linux/uio.h>
+#include <linux/buffer_head.h>
 #include "ext2.h"
 #include "xattr.h"
 #include "acl.h"
@@ -153,7 +154,7 @@ int ext2_fsync(struct file *file, loff_t start, loff_t end, int datasync)
 	int ret;
 	struct super_block *sb = file->f_mapping->host->i_sb;
 
-	ret = generic_file_fsync(file, start, end, datasync);
+	ret = generic_buffers_fsync(file, start, end, datasync);
 	if (ret == -EIO)
 		/* We don't really know where the IO error happened... */
 		ext2_error(sb, __func__,