Re: [PATCH] init/do_mounts.c: treat EROFS like EACCES

[Andrew Morton <akpm@linux-foundation.org>]

On Wed, 18 Jun 2014 18:12:44 +0200 Philippe De Muyter <phdm@macqel.be> wrote:

> some combinations of filesystem and block device (at least vfat on mmc)
> yield -EROFS instead of -EACCES when the device is read-only.  Retry
> mounting with MS_RDONLY set, just like for the EACCES case, instead of
> failing directly.
> 
> ...
>
> --- a/init/do_mounts.c
> +++ b/init/do_mounts.c
> @@ -394,6 +394,7 @@ retry:
>  			case 0:
>  				goto out;
>  			case -EACCES:
> +			case -EROFS:
>  				flags |= MS_RDONLY;
>  				goto retry;
>  			case -EINVAL:

hm, what's going on here.  I'd have thought it to be very logical that
file_system_type.mount() would return EROFS if the device is read-only!
But I'm suspecting that there is some convention that the fs is
supposed to return EACCES in this case.  So *perhaps* it is vfat-on-mmc
which needs fixing.  Dunno.

Al, are you able to shed light?