Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752832Ab3IFOqZ (ORCPT ); Fri, 6 Sep 2013 10:46:25 -0400 Received: from mx1.redhat.com ([209.132.183.28]:20316 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751225Ab3IFOqX (ORCPT ); Fri, 6 Sep 2013 10:46:23 -0400 Message-ID: <5229E9BF.5020604@redhat.com> Date: Fri, 06 Sep 2013 16:42:07 +0200 From: Jerome Marchand User-Agent: Mozilla/5.0 (X11; Linux i686; rv:17.0) Gecko/20130110 Thunderbird/17.0.2 MIME-Version: 1.0 To: Sergey Senozhatsky CC: Greg Kroah-Hartman , Minchan Kim , devel@driverdev.osuosl.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] staging: zram: minimize `slot_free_lock' usage References: <20130906134706.GA2238@swordfish.minsk.epam.com> In-Reply-To: <20130906134706.GA2238@swordfish.minsk.epam.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1804 Lines: 54 On 09/06/2013 03:47 PM, Sergey Senozhatsky wrote: > Calling handle_pending_slot_free() for every RW operation may > cause unneccessary slot_free_lock locking, because most likely > process will see NULL slot_free_rq. handle_pending_slot_free() > only when current detects that slot_free_rq is not NULL. > > Signed-off-by: Sergey Senozhatsky > > --- > > drivers/staging/zram/zram_drv.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/drivers/staging/zram/zram_drv.c b/drivers/staging/zram/zram_drv.c > index 91d94b5..17386e2 100644 > --- a/drivers/staging/zram/zram_drv.c > +++ b/drivers/staging/zram/zram_drv.c > @@ -532,14 +532,15 @@ static int zram_bvec_rw(struct zram *zram, struct bio_vec *bvec, u32 index, > { > int ret; > > + if (zram->slot_free_rq) > + handle_pending_slot_free(zram); > + Calling handle_pending_slot_free() without holding zram->lock? That's racy. Jerome > if (rw == READ) { > down_read(&zram->lock); > - handle_pending_slot_free(zram); > ret = zram_bvec_read(zram, bvec, index, offset, bio); > up_read(&zram->lock); > } else { > down_write(&zram->lock); > - handle_pending_slot_free(zram); > ret = zram_bvec_write(zram, bvec, index, offset); > up_write(&zram->lock); > } > > -- > 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/ > -- 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/