Re: [PATCH] block: forbid to re-enable I/O stat accounting

[Andrew Morton]

Please fix your email headers - what I received was

From: Jerome Marchand <jmarchan@xxxxxxxxxx>
To: unlisted-recipients:;;@imap1.linux-foundation.org (no To-header on input)
Cc: Jens Axboe <axboe@xxxxxxxxx>


On Thu, 19 Mar 2009 11:36:50 +0100 Jerome Marchand <jmarchan@xxxxxxxxxx> wrote:

> When we stop I/O stat accounting we stop to update the in-flight
> requests counter and we need this counter to be reliable for
> accounting I/O stats. Unfortunately updating in_flight field may
> affect performance. So, until we have a better solution, just forbid
> to re-enable I/O stat accounting after it has been disabled.

hm.  Is it really so hard to just quiesce the device until all in-flight
requests have drained?  freeze_bdev() might be a suitable starting point?

--
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/