Re: [PATCH] fix floppy.c to store correct ro/rw status in underlying gendisk

[Evgeny Stambulchik <Evgeny.Stambulchik@weizmann.ac.il>]

Jon Masters wrote:

> Let me know if this fixes it for you - should bomb out now if you try.
> The error isn't the cleanest (blame mount), but it does fail.

This works fine, thanks! For what it worth, though, mount -o remount,rw 
says remounting read-only yet still returns success. (Opposite to 
busybox, which now says "Permission denied" - rather misleading, but at 
least it fails).

My question is, shouldn't it be implemented at a more generic level? 
Floppy is just one example. Others are all kind of USB storage, ZIP/Jazz 
drives, and even normal SCSI disks (which have a RO jumper - at least 
some of them do).

I got an ancient USB disk on key with a write-protection switch. When I 
plug it in in the RO mode, everything goes exactly as it was (before 
your patch) with floppy. Now something interesting:
1. The thingy is plugged in RW and mounted
2. While connected, I switch it to RO
   dmesg says:
   -> SCSI device sda: 129024 512-byte hdwr sectors (66 MB)
   -> sda: Write Protect is on
   -> sda: Mode Sense: 03 00 80 00
   -> sda: assuming drive cache: write through
3.
# mount -o remount,rw  /mnt
mount: block device /dev/sda1 is write-protected, mounting read-only
# echo $?
0

So it seems there is some layer in bd which does know about RO status 
(and furthermore it's set by hot events)?

Regards,

Evgeny