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SubjectRe: [PATCH] ide write barrier support
On Mon, Oct 13, 2003 at 04:08:58PM +0200, Jens Axboe wrote:
> +/*
> + * preempt pending requests, and store this cache flush for immediate
> + * execution
> + */
> +static struct request *ide_queue_flush_cmd(ide_drive_t *drive,
> + struct request *rq, int post)
> +{
> + struct request *flush_rq = &HWGROUP(drive)->wrq;
> +
> + blkdev_dequeue_request(rq);
> +
> + memset(drive->special_buf, 0, sizeof(drive->special_buf));
> +
> + ide_init_drive_cmd(flush_rq);
> +
> + flush_rq->buffer = drive->special_buf;
> + flush_rq->special = rq;
> + flush_rq->buffer[0] = WIN_FLUSH_CACHE;
> +
> + if (drive->id->cfs_enable_2 & 0x2400)
> + flush_rq->buffer[0] = WIN_FLUSH_CACHE_EXT;
> +
> + if (!post) {
> + drive->doing_barrier = 1;
> + flush_rq->flags |= REQ_BAR_PREFLUSH;
> + } else
> + flush_rq->flags |= REQ_BAR_POSTFLUSH;
> +
> + flush_rq->flags |= REQ_STARTED;
> + list_add(&flush_rq->queuelist, &drive->queue->queue_head);
> + return flush_rq;
> +}

AFAICS you're missing some code that could be a major data corrupter:

FLUSH CACHE [EXT] may return before it's complete. You need to create
an issue loop, that does FLUSH CACHE [EXT] and reads the result. If the
result indicates the flush cache was partial, then you need to re-issue
the flush. Lather, rinse, repeat until flush cache indicates all data
is really flushed.

Jeff



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