From 9768a10dd35c6bca9ea58ae23bd5d5c2500d7005 Mon Sep 17 00:00:00 2001
From: Joe Thornber <ejt@redhat.com>
Date: Thu, 9 Nov 2017 11:41:05 -0500
Subject: [PATCH] dm cache policy smq: allocate cache blocks in order
Git-commit: 9768a10dd35c6bca9ea58ae23bd5d5c2500d7005
Patch-mainline: v4.15-rc1
References: bsc#1093023

Previously, cache blocks were being allocated in reverse order.  Fix
this by pulling the block off the head of the free list.

Shouldn't have any impact on performance or latency but it is more
correct to have the cache blocks allocated/mapped in ascending order.
This fix will slightly increase the chances of two adjacent oblocks
being in adjacent cblocks.

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Coly Li <colyli@suse.de>

---
 drivers/md/dm-cache-policy-smq.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/drivers/md/dm-cache-policy-smq.c b/drivers/md/dm-cache-policy-smq.c
index 58be846ba5b9..4ab23d0075f6 100644
--- a/drivers/md/dm-cache-policy-smq.c
+++ b/drivers/md/dm-cache-policy-smq.c
@@ -213,6 +213,19 @@ static void l_del(struct entry_space *es, struct ilist *l, struct entry *e)
 		l->nr_elts--;
 }
 
+static struct entry *l_pop_head(struct entry_space *es, struct ilist *l)
+{
+	struct entry *e;
+
+	for (e = l_head(es, l); e; e = l_next(es, e))
+		if (!e->sentinel) {
+			l_del(es, l, e);
+			return e;
+		}
+
+	return NULL;
+}
+
 static struct entry *l_pop_tail(struct entry_space *es, struct ilist *l)
 {
 	struct entry *e;
@@ -719,7 +732,7 @@ static struct entry *alloc_entry(struct entry_alloc *ea)
 	if (l_empty(&ea->free))
 		return NULL;
 
-	e = l_pop_tail(ea->es, &ea->free);
+	e = l_pop_head(ea->es, &ea->free);
 	init_entry(e);
 	ea->nr_allocated++;
 
-- 
2.16.3