linux-kernel - Write-only stuff in CFQ data structures

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Message-ID: <20070706145131.GB11067@localhost.sw.ru>
Date:	Fri, 6 Jul 2007 18:51:32 +0400
From:	Alexey Dobriyan <adobriyan@...ru>
To:	jens.axboe@...cle.com
Cc:	linux-kernel@...r.kernel.org, vtaras@...nvz.org
Subject: Write-only stuff in CFQ data structures

Jens, there are some write-only fields in cfq_data and cfq_queue to be
added in 2.6.22. I'm attaching patch to show what can be deleted, but
something suspicious is going on:

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index baef5fc..eed7020 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -109,9 +109,6 @@ struct cfq_data {
 	unsigned int cfq_slice_idle;
 
 	struct list_head cic_list;
-
-	sector_t new_seek_mean;
-	u64 new_seek_total;
 };
 
 /*
@@ -151,8 +148,6 @@ struct cfq_queue {
 
 	/* various state flags, see below */
 	unsigned int flags;
-
-	sector_t last_request_pos;
 };
 
 enum cfqq_state_flags {
@@ -1570,11 +1565,6 @@ cfq_update_io_seektime(struct cfq_data *cfqd, struct cfq_io_context *cic,
 	else
 		sdist = cic->last_request_pos - rq->sector;
 
-	if (!cic->seek_samples) {
-		cfqd->new_seek_total = (7*cic->seek_total + (u64)256*sdist) / 8;
-		cfqd->new_seek_mean = cfqd->new_seek_total / 256;
-	}
-
 	/*
 	 * Don't allow the seek distance to get too large from the
 	 * odd fragment, pagein, etc
@@ -1710,7 +1700,6 @@ cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
 	cfq_update_idle_window(cfqd, cfqq, cic);
 
 	cic->last_request_pos = rq->sector + rq->nr_sectors;
-	cfqq->last_request_pos = cic->last_request_pos;
 
 	if (cfqq == cfqd->active_queue) {
 		/*

-
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