[PATCH] inode: For readonly filesystem, func file_update_time should return -EROFS rather than zero.

[majianpeng <majianpeng@gmail.com>]

For ext2 mounted with errors=remount-ro, if write a file and because the
harddisk error, the fs became ro.But the following test can't return.

int main()
{
	int ret;
	int i = 0;
	char buff[SIZE];
	int fd = open("/opt/test", O_WRONLY|O_TRUNC|O_CREAT);

	if (fd < 0) {
		printf("open error %s\n", strerror(errno));
		return errno;
	}

	ret = write(fd, buff, SIZE);
	lseek(fd, 0, 0);

	while (1) {
		ret = write(fd, buff, SIZE);
		if (ret < 0) {
			printf("write error %s\n", strerror(errno));
			break;
		}
		lseek(fd, 0, 0);
		i++;
	}
	printf("write count=%d\n", i);
	close(fd);

	return 0;
}

For ext3/ext4, because jbd the test can return. But for ext2, because no
jbd and not reading bitmap from harddisk, the test continue.

So we should add check readonly-fs on write-path. Func file_update_time
already check the readonly flag,but it can't return -EROFS.
For readonly-fs, it can't update a/c/m time of file,it should return
-EROFS rather than zero.

Signed-off-by: Jianpeng Ma <majianpeng@gmail.com>
---
 fs/inode.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/inode.c b/fs/inode.c
index b33ba8e..65302c1 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -1644,8 +1644,9 @@ int file_update_time(struct file *file)
 		return 0;
 
 	/* Finally allowed to write? Takes lock. */
-	if (__mnt_want_write_file(file))
-		return 0;
+	ret = __mnt_want_write_file(file);
+	if (ret)
+		return ret;
 
 	ret = update_time(inode, &now, sync_it);
 	__mnt_drop_write_file(file);
-- 
1.8.4