linux-kernel - Re: [PATCH] REQ-flags to/from BIO-flags bugfix

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Date:	Wed, 12 Dec 2007 08:18:14 -0700
From:	Matthew Wilcox <matthew@....cx>
To:	Boaz Harrosh <bharrosh@...asas.com>
Cc:	James Bottomley <James.Bottomley@...senPartnership.com>,
	Jens Axboe <jens.axboe@...cle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Gabriel C <nix.or.die@...glemail.com>,
	linux-kernel@...r.kernel.org, linux-scsi@...r.kernel.org,
	Hannes Reinecke <hare@...e.de>
Subject: Re: [PATCH] REQ-flags to/from BIO-flags bugfix

On Wed, Dec 12, 2007 at 01:03:10PM +0200, Boaz Harrosh wrote:
>  - BIO flags bio->bi_rw and REQ flags req->cmd_flags no longer match.
>    Remove comments and do a proper translation between the 2 systems.

I'd rather see them resynchronised ... in a way that makes it obvious
that they should be desynced again:

I don't know whether BIO_RW_BARRIER is __REQ_SOFTBARRIER or
__REQ_HARDBARRIER, so I didn't include that in this patch.  There also
doesn't seem to be a __REQ equivalent to BIO_RW_AHEAD, but we can do
the other four bits (and leave gaps for those two).

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index d18ee67..6aef34b 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -167,11 +167,13 @@ enum {
 };
 
 /*
- * request type modified bits. first three bits match BIO_RW* bits, important
+ * request type modified bits.  Don't change without looking at bi_rw flags
  */
 enum rq_flag_bits {
-	__REQ_RW,		/* not set, read. set, write */
-	__REQ_FAILFAST,		/* no low level driver retries */
+	__REQ_RW = BIO_RW,	/* not set, read. set, write */
+	__REQ_FAILFAST = BIO_RW_FAILFAST, /* no low level driver retries */
+	__REQ_RW_SYNC = BIO_RW_SYNC,	/* request is sync (O_DIRECT) */
+	__REQ_RW_META = BIO_RW_META,	/* metadata io request */
 	__REQ_SORTED,		/* elevator knows about this request */
 	__REQ_SOFTBARRIER,	/* may not be passed by ioscheduler */
 	__REQ_HARDBARRIER,	/* may not be passed by drive either */
@@ -185,9 +187,7 @@ enum rq_flag_bits {
 	__REQ_QUIET,		/* don't worry about errors */
 	__REQ_PREEMPT,		/* set for "ide_preempt" requests */
 	__REQ_ORDERED_COLOR,	/* is before or after barrier */
-	__REQ_RW_SYNC,		/* request is sync (O_DIRECT) */
 	__REQ_ALLOCED,		/* request came from our alloc pool */
-	__REQ_RW_META,		/* metadata io request */
 	__REQ_NR_BITS,		/* stops here */
 };
 

-- 
Intel are signing my paycheques ... these opinions are still mine
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours.  We can't possibly take such
a retrograde step."
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