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Message-ID: <x49oc07sija.fsf@segfault.boston.devel.redhat.com>
Date: Tue, 02 Aug 2011 15:46:49 -0400
From: Jeff Moyer <jmoyer@...hat.com>
To: Vivek Goyal <vgoyal@...hat.com>
Cc: Shaohua Li <shli@...nel.org>, linux-kernel@...r.kernel.org,
Tejun Heo <tj@...nel.org>, Jens Axboe <jaxboe@...ionio.com>,
msnitzer@...hat.com
Subject: Re: [patch] blk-flush: fix flush policy calculation
Vivek Goyal <vgoyal@...hat.com> writes:
>> In testing, I did this:
>>
>> @@ -1817,6 +1817,14 @@ int blk_insert_cloned_request(struct
>> request_queue *q, struct request *rq)
>> return -EIO;
>> #endif
>>
>> + if ((rq->cmd_flags & (REQ_FLUSH|REQ_FUA)) && !q->flush_flags) {
>> + rq->cmd_flags &= ~(REQ_FLUSH|REQ_FUA);
>> + if (!blk_rq_bytes(rq)) {
>> + blk_end_request(rq, 0, 0);
>> + return 0;
>> + }
>> + }
>> +
>
> Will it make more sense to take care resetting flush/fua flags in
> blk_insert_flush()
Yes, that's much cleaner.
> and also the part which will end the request if request is empty.
Mmm-hmm.
I tried this, and it blew up in my face. ;-) Cloned requests from
device-mapper-land have rq->end_io filled in, which causes
blk_insert_flush to BUG here:
BUG_ON(rq->end_io);
So, we can take the usual route of trying to squirrel away a pointer,
and reinstate that after the flush_data_end_io. Or, perhaps someone has
a more clever idea, that might keep us from further expanding struct
request...?
Cheers,
Jeff
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