Re: [PATCH] SMP race in ext2 - metadata corruption.

[Vojtech Pavlik]

On Thu, Apr 26, 2001 at 01:08:25PM -0700, Linus Torvalds wrote:

> On Thu, 26 Apr 2001, Alexander Viro wrote:
> > On Thu, 26 Apr 2001, Andrea Arcangeli wrote:
> > >
> > > how can the read in progress see a branch that we didn't spliced yet? We
> >
> > fd = open("/dev/hda1", O_RDONLY);
> > read(fd, buf, sizeof(buf));
> 
> Note that I think all these arguments are fairly bogus.  Doing things like
> "dump" on a live filesystem is stupid and dangerous (in my opinion it is
> stupid and dangerous to use "dump" at _all_, but that's a whole 'nother
> discussion in itself), and there really are no valid uses for opening a
> block device that is already mounted. More importantly, I don't think
> anybody actually does.

Actually this is done quite often, even on mounted fs's:

hdparm -t /dev/hda

> The fact that you _can_ do so makes the patch valid, and I do agree with
> Al on the "least surprise" issue. I've already applied the patch, in fact.
> But the fact is that nobody should ever do the thing that could cause
> problems.

-- 
Vojtech Pavlik
SuSE Labs