From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754810AbdBOXSH (ORCPT ); Wed, 15 Feb 2017 18:18:07 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:53697 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754624AbdBOXSE (ORCPT ); Wed, 15 Feb 2017 18:18:04 -0500 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Rabin Vincent" , "Sebastian Andrzej Siewior" , "Colin Cross" , "Kees Cook" , "Anton Vorontsov" , "Guenter Roeck" , "Tony Luck" Date: Wed, 15 Feb 2017 22:41:40 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 037/306] pstore/core: drop cmpxchg based updates In-Reply-To: X-SA-Exim-Connect-IP: 2a02:8011:400e:2:6f00:88c8:c921:d332 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.40-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Sebastian Andrzej Siewior commit d5a9bf0b38d2ac85c9a693c7fb851f74fd2a2494 upstream. I have here a FPGA behind PCIe which exports SRAM which I use for pstore. Now it seems that the FPGA no longer supports cmpxchg based updates and writes back 0xff…ff and returns the same. This leads to crash during crash rendering pstore useless. Since I doubt that there is much benefit from using cmpxchg() here, I am dropping this atomic access and use the spinlock based version. Cc: Anton Vorontsov Cc: Colin Cross Cc: Kees Cook Cc: Tony Luck Cc: Rabin Vincent Tested-by: Rabin Vincent Signed-off-by: Sebastian Andrzej Siewior Reviewed-by: Guenter Roeck [kees: remove "_locked" suffix since it's the only option now] Signed-off-by: Kees Cook Signed-off-by: Ben Hutchings --- fs/pstore/ram_core.c | 43 ++----------------------------------------- 1 file changed, 2 insertions(+), 41 deletions(-) --- a/fs/pstore/ram_core.c +++ b/fs/pstore/ram_core.c @@ -47,43 +47,10 @@ static inline size_t buffer_start(struct return atomic_read(&prz->buffer->start); } -/* increase and wrap the start pointer, returning the old value */ -static size_t buffer_start_add_atomic(struct persistent_ram_zone *prz, size_t a) -{ - int old; - int new; - - do { - old = atomic_read(&prz->buffer->start); - new = old + a; - while (unlikely(new >= prz->buffer_size)) - new -= prz->buffer_size; - } while (atomic_cmpxchg(&prz->buffer->start, old, new) != old); - - return old; -} - -/* increase the size counter until it hits the max size */ -static void buffer_size_add_atomic(struct persistent_ram_zone *prz, size_t a) -{ - size_t old; - size_t new; - - if (atomic_read(&prz->buffer->size) == prz->buffer_size) - return; - - do { - old = atomic_read(&prz->buffer->size); - new = old + a; - if (new > prz->buffer_size) - new = prz->buffer_size; - } while (atomic_cmpxchg(&prz->buffer->size, old, new) != old); -} - static DEFINE_RAW_SPINLOCK(buffer_lock); /* increase and wrap the start pointer, returning the old value */ -static size_t buffer_start_add_locked(struct persistent_ram_zone *prz, size_t a) +static size_t buffer_start_add(struct persistent_ram_zone *prz, size_t a) { int old; int new; @@ -103,7 +70,7 @@ static size_t buffer_start_add_locked(st } /* increase the size counter until it hits the max size */ -static void buffer_size_add_locked(struct persistent_ram_zone *prz, size_t a) +static void buffer_size_add(struct persistent_ram_zone *prz, size_t a) { size_t old; size_t new; @@ -124,9 +91,6 @@ exit: raw_spin_unlock_irqrestore(&buffer_lock, flags); } -static size_t (*buffer_start_add)(struct persistent_ram_zone *, size_t) = buffer_start_add_atomic; -static void (*buffer_size_add)(struct persistent_ram_zone *, size_t) = buffer_size_add_atomic; - static void notrace persistent_ram_encode_rs8(struct persistent_ram_zone *prz, uint8_t *data, size_t len, uint8_t *ecc) { @@ -426,9 +390,6 @@ static void *persistent_ram_iomap(phys_a return NULL; } - buffer_start_add = buffer_start_add_locked; - buffer_size_add = buffer_size_add_locked; - if (memtype) va = ioremap(start, size); else