Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753950AbaG3MUX (ORCPT ); Wed, 30 Jul 2014 08:20:23 -0400 Received: from ip4-83-240-18-248.cust.nbox.cz ([83.240.18.248]:36793 "EHLO ip4-83-240-18-248.cust.nbox.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753023AbaG3MPe (ORCPT ); Wed, 30 Jul 2014 08:15:34 -0400 From: Jiri Slaby To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Benjamin LaHaise , Jens Axboe , Christoph Hellwig , Jiri Slaby Subject: [PATCH 3.12 73/94] aio: protect reqs_available updates from changes in interrupt handlers Date: Wed, 30 Jul 2014 14:15:02 +0200 Message-Id: <60714352c491ab477ae767582d18059e2534c5a7.1406722270.git.jslaby@suse.cz> X-Mailer: git-send-email 2.0.1 In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Benjamin LaHaise 3.12-stable review patch. If anyone has any objections, please let me know. =============== commit 263782c1c95bbddbb022dc092fd89a36bb8d5577 upstream. As of commit f8567a3845ac05bb28f3c1b478ef752762bd39ef it is now possible to have put_reqs_available() called from irq context. While put_reqs_available() is per cpu, it did not protect itself from interrupts on the same CPU. This lead to aio_complete() corrupting the available io requests count when run under a heavy O_DIRECT workloads as reported by Robert Elliott. Fix this by disabling irq updates around the per cpu batch updates of reqs_available. Many thanks to Robert and folks for testing and tracking this down. Reported-by: Robert Elliot Tested-by: Robert Elliot Signed-off-by: Benjamin LaHaise Cc: Jens Axboe , Christoph Hellwig Signed-off-by: Jiri Slaby --- fs/aio.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/fs/aio.c b/fs/aio.c index e609e15f36b9..6d68e01dc7ca 100644 --- a/fs/aio.c +++ b/fs/aio.c @@ -830,16 +830,20 @@ void exit_aio(struct mm_struct *mm) static void put_reqs_available(struct kioctx *ctx, unsigned nr) { struct kioctx_cpu *kcpu; + unsigned long flags; preempt_disable(); kcpu = this_cpu_ptr(ctx->cpu); + local_irq_save(flags); kcpu->reqs_available += nr; + while (kcpu->reqs_available >= ctx->req_batch * 2) { kcpu->reqs_available -= ctx->req_batch; atomic_add(ctx->req_batch, &ctx->reqs_available); } + local_irq_restore(flags); preempt_enable(); } @@ -847,10 +851,12 @@ static bool get_reqs_available(struct kioctx *ctx) { struct kioctx_cpu *kcpu; bool ret = false; + unsigned long flags; preempt_disable(); kcpu = this_cpu_ptr(ctx->cpu); + local_irq_save(flags); if (!kcpu->reqs_available) { int old, avail = atomic_read(&ctx->reqs_available); @@ -869,6 +875,7 @@ static bool get_reqs_available(struct kioctx *ctx) ret = true; kcpu->reqs_available--; out: + local_irq_restore(flags); preempt_enable(); return ret; } -- 2.0.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/