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

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