Re: Getting FS access events

H. Peter Anvin
2001-05-15T19:29:45Z

Followup to: <5.1.0.14.2.20010515105633.00a22c10@pop.cus.cam.ac.uk>
By author: Anton Altaparmakov <aia21@cam.ac.uk>
In newsgroup: linux.dev.kernel
>
> They shouldn't, but maybe some stupid utility or a typo will do it creating
> two incoherent copies of the same block on the device. -> Bad Things can
> happen.
>
> Can't we simply stop people from doing it by say having mount lock the
> device from further opens (and vice versa of course, doing a "dd" should
> result in lock of device preventing a mount during the duration of "dd"). -
> Wouldn't this be a good thing, guaranteeing that problems cannot happen
> while not incurring any overhead except on device open/close? Or is this a
> matter of "give the user enough rope"? - If proper rw locking is
> implemented it could allow simultaneous -o ro mount with a dd from the
> device but do exclusive write locking, for example, for maximum flexibility.
>

This would leave no way (without introducing new interfaces) to write,
for example, the boot block on an ext2 filesystem. Note that the
bootblock (defined as the first 1024 bytes) is not actually used by
the filesystem, although depending on the block size it may share a
block with the superblock (if blocksize > 1024).

-hpa

--
<hpa@transmeta.com> at work, <hpa@zytor.com> in private!
"Unix gives you enough rope to shoot yourself in the foot."