Re: [PATCH 1/2] fs: Do not dispatch FITRIM through separatesuper_operation

[James Bottomley]

On Sun, 2010-11-21 at 14:07 -0500, Valdis.Kletnieks@xxxxxx wrote:
> On Fri, 19 Nov 2010 09:53:52 EST, Mark Lord said:
> > On 10-11-19 09:40 AM, Chris Mason wrote:
> > >
> > > We've been told that online and constant trimming is the default in
> > > windows7.   The ssds are most likely to just start ignoring the trims
> > > they can't service efficiently.
> > 
> > Win7 collects multiple TRIM ranges over time and batches them as single TRIMs
> > (as reported to me by an SSD vendor who traced it with a SATA analyzer,
> >   and who also apparently has "inside info").
> 
> What should happen if we have (for instance) a "collect 64 trims at a time" policy,
> and the system crashes at trim number 47? (Probably not an issue if you're
> doing non-deterministic trim, but is an exposure if you're relying on deterministic
> trim for security reasons)

I think it's about the third time in the thread this has been said but
just in case anyone else missed it: TRIM != SECURE ERASE.
TRIM/UNMAP/WRITE_SAME are used to provide optional information about
which blocks the filesystem doesn't care about.  They have no bearing on
information security which is preserved by separate mechanisms.

James


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/