linux-kernel - [PATCH 11/41] block: filter flush bio's in __generic_make

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Date:	Fri,  3 Sep 2010 12:29:26 +0200
From:	Tejun Heo <tj@...nel.org>
To:	jaxboe@...ionio.com, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, linux-scsi@...r.kernel.org,
	linux-ide@...r.kernel.org, linux-raid@...r.kernel.org,
	dm-devel@...hat.com, hch@....de, konishi.ryusuke@....ntt.co.jp,
	James.Bottomley@...e.de, tytso@....edu, chris.mason@...cle.com,
	swhiteho@...hat.com, vst@...b.net, jack@...e.cz,
	rwheeler@...hat.com, hare@...e.de, neilb@...e.de,
	rusty@...tcorp.com.au, mst@...hat.com, snitzer@...hat.com,
	k-ueda@...jp.nec.com, mpatocka@...hat.com
Cc:	Tejun Heo <tj@...nel.org>
Subject: [PATCH 11/41] block: filter flush bio's in __generic_make_request()

There are a number of make_request based drivers which don't support
cache flushes.  Filter out flush bio's in __generic_make_request() so
that they don't have to worry about them.  All FLUSH/FUA requests with
data are converted to regular IO requests and empty ones are completed
immediately.

Signed-off-by: Tejun Heo <tj@...nel.org>
---
 block/blk-core.c |   13 +++++++++++++
 1 files changed, 13 insertions(+), 0 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index 18455c4..495bdc4 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1509,6 +1509,19 @@ static inline void __generic_make_request(struct bio *bio)
 		if (bio_check_eod(bio, nr_sectors))
 			goto end_io;
 
+		/*
+		 * Filter flush bio's early so that make_request based
+		 * drivers without flush support don't have to worry
+		 * about them.
+		 */
+		if ((bio->bi_rw & (REQ_FLUSH | REQ_FUA)) && !q->flush_flags) {
+			bio->bi_rw &= ~(REQ_FLUSH | REQ_FUA);
+			if (!nr_sectors) {
+				err = 0;
+				goto end_io;
+			}
+		}
+
 		if ((bio->bi_rw & REQ_DISCARD) &&
 		    (!blk_queue_discard(q) ||
 		     ((bio->bi_rw & REQ_SECURE) &&
-- 
1.7.1

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