linux-kernel - [PATCH] lib/genalloc.c: Start search from start of chunk

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Date:   Mon, 24 Oct 2016 18:58:13 -0700
From:   Daniel Mentz <danielmentz@...gle.com>
To:     linux-kernel@...r.kernel.org
Cc:     Daniel Mentz <danielmentz@...gle.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Arnd Bergmann <arnd@...db.de>,
        Catalin Marinas <catalin.marinas@....com>,
        Dan Williams <dan.j.williams@...el.com>,
        David Riley <davidriley@...omium.org>,
        Eric Miao <eric.y.miao@...il.com>,
        Grant Likely <grant.likely@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Haojian Zhuang <haojian.zhuang@...il.com>,
        Huang Ying <ying.huang@...el.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        Kevin Hilman <khilman@...prootsystems.com>,
        Laura Abbott <lauraa@...eaurora.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Mauro Carvalho Chehab <m.chehab@...sung.com>,
        Olof Johansson <olof@...om.net>,
        Ritesh Harjain <ritesh.harjani@...il.com>,
        Rob Herring <rob.herring@...xeda.com>,
        Russell King <linux@....linux.org.uk>,
        Sekhar Nori <nsekhar@...com>, Takashi Iwai <tiwai@...e.de>,
        Thadeu Lima de Souza Cascardo <cascardo@...ux.vnet.ibm.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Vinod Koul <vinod.koul@...el.com>,
        Vladimir Zapolskiy <vladimir_zapolskiy@...tor.com>,
        Will Deacon <will.deacon@....com>
Subject: [PATCH] lib/genalloc.c: Start search from start of chunk

gen_pool_alloc_algo() iterates over all chunks of a pool trying to find
a contiguous block of memory that satisfies the allocation request.
The search should start at address zero of every chunk. However, as the
code stands today, this is only true for the first chunk. Due to a bug,
the search of subsequent chunks starts somewhere else:

The variables start_bit and end_bit are meant to describe the range that
should be searched and should be reset for every chunk that is searched.
Today, the code fails to reset start_bit to 0.

Fixes: 7f184275aa30 ("lib, Make gen_pool memory allocator lockless")
Cc: Andi Kleen <ak@...ux.intel.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Arnd Bergmann <arnd@...db.de>
Cc: Catalin Marinas <catalin.marinas@....com>
Cc: Dan Williams <dan.j.williams@...el.com>
Cc: David Riley <davidriley@...omium.org>
Cc: Eric Miao <eric.y.miao@...il.com>
Cc: Grant Likely <grant.likely@...aro.org>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Haojian Zhuang <haojian.zhuang@...il.com>
Cc: Huang Ying <ying.huang@...el.com>
Cc: Jaroslav Kysela <perex@...ex.cz>
Cc: Kevin Hilman <khilman@...prootsystems.com>
Cc: Laura Abbott <lauraa@...eaurora.org>
Cc: Liam Girdwood <lgirdwood@...il.com>
Cc: Mark Brown <broonie@...nel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc: Mauro Carvalho Chehab <m.chehab@...sung.com>
Cc: Olof Johansson <olof@...om.net>
Cc: Ritesh Harjain <ritesh.harjani@...il.com>
Cc: Rob Herring <rob.herring@...xeda.com>
Cc: Russell King <linux@....linux.org.uk>
Cc: Sekhar Nori <nsekhar@...com>
Cc: Takashi Iwai <tiwai@...e.de>
Cc: Thadeu Lima de Souza Cascardo <cascardo@...ux.vnet.ibm.com>
Cc: Thierry Reding <thierry.reding@...il.com>
Cc: Vinod Koul <vinod.koul@...el.com>
Cc: Vladimir Zapolskiy <vladimir_zapolskiy@...tor.com>
Cc: Will Deacon <will.deacon@....com>
Signed-off-by: Daniel Mentz <danielmentz@...gle.com>
---
 lib/genalloc.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/lib/genalloc.c b/lib/genalloc.c
index 0a11396..144fe6b 100644
--- a/lib/genalloc.c
+++ b/lib/genalloc.c
@@ -292,7 +292,7 @@ unsigned long gen_pool_alloc_algo(struct gen_pool *pool, size_t size,
 	struct gen_pool_chunk *chunk;
 	unsigned long addr = 0;
 	int order = pool->min_alloc_order;
-	int nbits, start_bit = 0, end_bit, remain;
+	int nbits, start_bit, end_bit, remain;
 
 #ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
 	BUG_ON(in_nmi());
@@ -307,6 +307,7 @@ unsigned long gen_pool_alloc_algo(struct gen_pool *pool, size_t size,
 		if (size > atomic_read(&chunk->avail))
 			continue;
 
+		start_bit = 0;
 		end_bit = chunk_size(chunk) >> order;
 retry:
 		start_bit = algo(chunk->bits, end_bit, start_bit,
-- 
2.8.0.rc3.226.g39d4020