From: Kent Overstreet <kmo@daterainc.com>
Date: Fri, 12 Jul 2013 02:43:21 +0000 (-0700)
Subject: bcache: Fix GC_SECTORS_USED() calculation
X-Git-Url: http://git.mmlx.us/?a=commitdiff_plain;h=99e56bf5abce5131746397a2ce551fd92ca8f342;p=linux-edison.git

bcache: Fix GC_SECTORS_USED() calculation

commit 29ebf465b9050f241c4433a796a32e6c896a9dcd upstream.

Part of the job of garbage collection is to add up however many sectors
of live data it finds in each bucket, but that doesn't work very well if
it doesn't reset GC_SECTORS_USED() when it starts. Whoops.

This wouldn't have broken anything horribly, but allocation tries to
preferentially reclaim buckets that are mostly empty and that's not
gonna work with an incorrect GC_SECTORS_USED() value.

Signed-off-by: Kent Overstreet <kmo@daterainc.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
index 7a5658f04e6..7b687a6f3de 100644
--- a/drivers/md/bcache/btree.c
+++ b/drivers/md/bcache/btree.c
@@ -1419,8 +1419,10 @@ static void btree_gc_start(struct cache_set *c)
 	for_each_cache(ca, c, i)
 		for_each_bucket(b, ca) {
 			b->gc_gen = b->gen;
-			if (!atomic_read(&b->pin))
+			if (!atomic_read(&b->pin)) {
 				SET_GC_MARK(b, GC_MARK_RECLAIMABLE);
+				SET_GC_SECTORS_USED(b, 0);
+			}
 		}
 
 	for (d = c->devices;