linux-kernel - Re: [Bug 12713] Hang on resume from hibernation, apparently as result of 213d9417fec

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Date:	Mon, 16 Feb 2009 02:07:59 +0200
From:	"Michael S. Tsirkin" <m.s.tsirkin@...il.com>
To:	pavel@...e.cz, rjw@...k.pl, linux-pm@...ts.linux-foundation.org,
	axboe@...nel.dk,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	bugme-daemon@...zilla.kernel.org
Subject: Re: [Bug 12713] Hang on resume from hibernation, apparently as result 
	of 213d9417fec

On Mon, Feb 16, 2009 at 2:05 AM, Michael S. Tsirkin
<m.s.tsirkin@...il.com> wrote:
> Summary: seem to need to revert 213d9417fec62ef4c3675621b9364a667954d4dd
> to fix resume from hibernation. Bugzilla entry created:
> http://bugzilla.kernel.org/show_bug.cgi?id=12713

Looking over this, I see something strange in the commit in question:

diff --git a/include/linux/bio.h b/include/linux/bio.h
index 5175aa3..f53568c 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -163,12 +163,15 @@ struct bio {
 #define BIO_RW         0       /* Must match RW in req flags (blkdev.h) */
 #define BIO_RW_AHEAD   1       /* Must match FAILFAST in req flags */
 #define BIO_RW_BARRIER 2
-#define BIO_RW_SYNC    3
-#define BIO_RW_META    4
-#define BIO_RW_DISCARD 5
-#define BIO_RW_FAILFAST_DEV            6
-#define BIO_RW_FAILFAST_TRANSPORT      7
-#define BIO_RW_FAILFAST_DRIVER         8
+#define BIO_RW_SYNCIO  3
+#define BIO_RW_UNPLUG  4
+#define BIO_RW_META    5
+#define BIO_RW_DISCARD 6
+#define BIO_RW_FAILFAST_DEV            7
+#define BIO_RW_FAILFAST_TRANSPORT      8
+#define BIO_RW_FAILFAST_DRIVER         9
+
+#define BIO_RW_SYNC    (BIO_RW_SYNCIO | BIO_RW_UNPLUG)

 /*
  * upper 16 bits of bi_rw define the io priority of this bio

I haven't read the code in depth, but taking running numbers and doing
bitwise "or"
on them looks a bit strange to me.
So here BIO_RW_SYNC is (3 | 4) = 7, that is the same as BIO_RW_FAILFAST_DEV.
So for example bio_failfast_dev and bio_sync are the same.

Jens, could you comment on this please? Is this intentional?

-- 
MST
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