On Sun, 3 Nov 2002, Pavel Machek wrote:
>
> How do I quiesce a queue? Is it ll_rw_blk stuff?
Just send a request down the request list, and make sure that
- the command is marked as being non-mergeable or re-orderable by
software (as all special commands are)
- the command is not re-orderable / mergeable by hardware (and since the
command in question would be something like "flush" or "spindown",
hardware really would be quite broken if it re-ordered it ;)
and then just wait for its completion.
The code is not that complicated, it looks roughly something like
struct request *rq;
rq = blk_get_request(q, WRITE, __GFP_WAIT);
rq->flags = REQ_BLOCK_PC;
rq->data = NULL;
rq->data_len = 0;
rq->timeout = 5*HZ; /* Or whatever */
memset(rq->cmd, 0, sizeof(rq->cmd));
rq->cmd[0] = SYNCHRONIZE_CACHE;
.. fill in whatever bytes the SYNCHRONIZE_CACHE cmd needs ..
rq->cmd_len = 10;
err = blk_do_rq(q, bdev, rq);
blk_put_request(rq);
and you're done. The above should work pretty much on all block drivers
out there, btw: the ones that don't understand SCSI commands should just
ignore requests that aren't the regular REQ_CMD commands.
See drivers/block/scsi_ioctl.c for other examples of sending down commands
to block devices.
Linus
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This archive was generated by hypermail 2b29 : Thu Nov 07 2002 - 22:00:31 EST