From: Joseph Glanville <joseph.glanville@orionvm.com.au>
To: Tejun Heo <tj@kernel.org>
Cc: NeilBrown <neilb@suse.de>,
Kent Overstreet <koverstreet@google.com>,
Jens Axboe <axboe@kernel.dk>,
Philipp Reisner <philipp.reisner@linbit.com>,
linux-kernel@vger.kernel.org, Christoph Hellwig <hch@lst.de>,
Vivek Goyal <vgoyal@redhat.com>,
drbd-dev@lists.linbit.com
Subject: Re: [Drbd-dev] FLUSH/FUA documentation & code discrepancy
Date: Thu, 13 Sep 2012 09:12:25 +1000 [thread overview]
Message-ID: <CAOzFzEjCf7ZPbheq-tfhts-E=Ep1kvn0muksaaTFqJ=cMm772w@mail.gmail.com> (raw)
In-Reply-To: <20120912185824.GS7677@google.com>
On 13 September 2012 04:58, Tejun Heo <tj@kernel.org> wrote:
> Hello,
>
> On Tue, Sep 11, 2012 at 10:25:01AM +0200, Lars Ellenberg wrote:
>> Or do we have a better place to document write ordering requirements?
>>
>> "To enforce write-after-write dependencies, you *have* to drain the
>> queue (do we have a generic interface available for that?),
>> or at least wait for the completion of all the requests you
>> (potentially) depend upon, before even submitting the dependent request.
>>
>> Additionally, to avoid integrity issues due to volatile caches,
>> you need to use FLUSH/FUA as appropriate."
>
> I think it would be best to note the lack of any ordering guarantee in
> the comment of bio_submit()? Any one interested in submitting a
> patch?
>
> Thanks.
>
> --
> tejun
> --
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Something along the lines of this?
diff --git a/block/blk-core.c b/block/blk-core.c
index 4b4dbdf..68b5671 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1809,6 +1809,9 @@ EXPORT_SYMBOL(generic_make_request);
* uses that function to do most of the work. Both are fairly rough
* interfaces; @bio must be presetup and ready for I/O.
*
+ * Ordering of requests is not guaranteed, callers should drain the queue
+ * and issue a flush before submission of any dependent bios.
+ *
*/
void submit_bio(int rw, struct bio *bio)
{
--
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next prev parent reply other threads:[~2012-09-12 23:12 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-04 12:32 FLUSH/FUA documentation & code discrepancy Philipp Reisner
2012-09-04 22:46 ` Tejun Heo
2012-09-05 8:44 ` [Drbd-dev] " Philipp Reisner
2012-09-05 8:49 ` Tejun Heo
2012-09-05 10:07 ` Lars Ellenberg
2012-09-06 21:29 ` Tejun Heo
2012-09-07 8:42 ` Lars Ellenberg
2012-09-10 22:54 ` Tejun Heo
2012-09-10 23:06 ` Tejun Heo
2012-09-10 23:12 ` Kent Overstreet
2012-09-10 23:31 ` Kent Overstreet
2012-09-11 5:58 ` NeilBrown
2012-09-11 8:25 ` Lars Ellenberg
2012-09-11 14:41 ` Vivek Goyal
2012-09-12 18:58 ` Tejun Heo
2012-09-12 23:12 ` Joseph Glanville [this message]
2012-09-12 23:20 ` Tejun Heo
2012-09-12 23:53 ` Joseph Glanville
2012-09-13 0:17 ` Joseph Glanville
2012-09-13 3:10 ` Joseph Glanville
2012-09-13 19:25 ` Tejun Heo
2012-09-11 14:34 ` Vivek Goyal
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