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

[majianpeng]

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 <majianp...@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