Re: ide errors in 7-rc1-mm1 and later

[Jens Axboe <axboe@suse.de>]

On Thu, Jun 10 2004, Bartlomiej Zolnierkiewicz wrote:
> > > - if you more than > 1 filesystem on the disk (quite likely scenario) it
> > >   can happen that barrier (flush) will fail for sector for file from the
> > >   other fs and later barrier for this other fs will succeed
> >
> > I don't understand this one.
> 
> Flush command can fail for sector which came into disk's write cache
> from some write request for some other fs on the same disk i.e.
> 
> write requests for fs 'a' (sector 'x' stays in write cache)
> write requests for fs 'b'
> commit log for fs 'b' -> barrier for fs 'b'
> barrier fails because of sector 'x'
> commit log for fs 'a' -> barrier for fs 'a'
> barrier succeeds

That's a bug in ide_complete_barrier(), like I outlined in the previous
mail you need to reissue the flush until no errors occur. A pre-flush
should not fail the barrier of course, since it has no relation to it.

> Such scenario is highly unlikely (disks do bad sector re-allocation
> on write) but not impossible (pool of sectors for remapping is unlimited).
> That's why I think it is a minor issue (but still worth to know about it).

Yes very, wants to work though...

-- 
Jens Axboe