Messages in this thread | | | Date | Fri, 21 Jan 2011 19:49:55 -0500 | From | Mike Snitzer <> | Subject | Re: [PATCH 3/3] block: reimplement FLUSH/FUA to support merge |
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On Fri, Jan 21 2011 at 10:59am -0500, Tejun Heo <tj@kernel.org> wrote:
> diff --git a/block/blk-flush.c b/block/blk-flush.c > index 8592869..cd73e93 100644 > --- a/block/blk-flush.c > +++ b/block/blk-flush.c > @@ -1,6 +1,69 @@ > /* > * Functions to sequence FLUSH and FUA writes. > + * > + * Copyright (C) 2011 Max Planck Institute for Gravitational Physics > + * Copyright (C) 2011 Tejun Heo <tj@kernel.org> > + * > + * This file is released under the GPLv2. > + * > + * REQ_{FLUSH|FUA} requests are decomposed to sequences consisted of three > + * optional steps - PREFLUSH, DATA and POSTFLUSH - according to the request > + * properties and hardware capability. > + * > + * If a request doesn't have data, only REQ_FLUSH makes sense, which > + * indicates a simple flush request. If there is data, REQ_FLUSH indicates > + * that the device cache should be flushed before the data is executed, and > + * REQ_FUA means that the data must be on non-volatile media on request > + * completion. > + * > + * If the device doesn't have writeback cache, FLUSH and FUA don't make any > + * difference. The requests are either completed immediately if there's no > + * data or executed as normal requests otherwise.
For devices without a writeback cache, I'm not seeing where pure flushes are completed immediately. But I do see where data is processed directly in blk_insert_flush().
> -struct request *blk_do_flush(struct request_queue *q, struct request *rq) > +/** > + * blk_abort_flush - @q is being aborted, abort flush requests ^^^^^^^^^^^^^^^ Small comment nit, s/blk_abort_flush/blk_abort_flushes/
> + * @q: request_queue being aborted > + * > + * To be called from elv_abort_queue(). @q is being aborted. Prepare all > + * FLUSH/FUA requests for abortion. > + * > + * CONTEXT: > + * spin_lock_irq(q->queue_lock) > + */ > +void blk_abort_flushes(struct request_queue *q)
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