Re: Changes to ide-probe.c in 2.6.9-rc2 causing improper detection

[Jens Axboe]

On Tue, Sep 14 2004, Jeff Garzik wrote:
> Alan Cox wrote:
> >On Maw, 2004-09-14 at 07:06, Jens Axboe wrote:
> >
> >>Alan, I bet there are a lot of these. Maybe we should consider letting
> >>the user manually flag support for FLUSH_CACHE, at least it is in their
> >>hands then.
> >
> >
> >You are assuming the drive supports "FLUSH_CACHE" just because it
> >doesn't error it. Thats a good way to have accidents. 
> >
> >The patch I posted originally did turn wcache off for barrier if no
> >flush cache support was present but had a small bug so that bit got
> >dropped.
> 
> 
> FWIW the libata test for checking whether it is OK to issue a flush is
> 
>         return ata_id_wcache_enabled(dev) ||
>                ata_id_has_flush(dev) ||
>                ata_id_has_flush_ext(dev);
> 
> and if it passes that test,
> 
>         if ((tf->flags & ATA_TFLAG_LBA48) &&
>             (ata_id_has_flush_ext(qc->dev)))
>                 tf->command = ATA_CMD_FLUSH_EXT;
>         else
>                 tf->command = ATA_CMD_FLUSH;
> 
> I wouldn't object to removing the "ata_id_wcache_enabled" test if people 
> feel that it is unsafe.

Alan says it's unsafe for some of his flash cards, and I do believe they
say they have write caching enabled.

-- 
Jens Axboe

-
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/