From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hans de Goede Subject: Re: 4.8-rc1 REGRESSION mmc-blk triggers WARN_ON(!host->claimed), related to: "drivers: use req op accessor" ? Date: Wed, 24 Aug 2016 10:47:07 +0200 Message-ID: <2a2ee1e8-8682-0647-a66d-04ceb54f58ec@redhat.com> References: <6e68ae5a-4b79-a636-2c46-5726cf2cc44b@redhat.com> <57BB23D0.3050606@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mx1.redhat.com ([209.132.183.28]:58510 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751742AbcHXIrN (ORCPT ); Wed, 24 Aug 2016 04:47:13 -0400 In-Reply-To: <57BB23D0.3050606@redhat.com> Sender: linux-mmc-owner@vger.kernel.org List-Id: linux-mmc@vger.kernel.org To: Mike Christie , Ulf Hansson , Jens Axboe , regressions@leemhuis.info Cc: "linux-mmc@vger.kernel.org" Hi, On 22-08-16 18:09, Mike Christie wrote: > On 08/21/2016 10:15 AM, Hans de Goede wrote: >> Hi All, >> >> With 4.8-rc1 I'm seeing WARN_ON(!host->claimed) triggering in both >> mmc_start_request() as well as in mmc_release_host(). The first >> indicating that we're executing mmc commands without doing >> mmc_claim_host() and the second one indicating that we're >> releasing the host without having claimed it first. >> >> The backtraces all point to mmc_blk_issue_rq(). I've done >> a very naive hack / workaround: >> >> --- a/drivers/mmc/card/block.c >> +++ b/drivers/mmc/card/block.c >> @@ -2151,9 +2151,7 @@ static int mmc_blk_issue_rq(struct mmc_queue *mq, >> struct request *req) >> struct mmc_host *host = card->host; >> unsigned long flags; >> >> - if (req && !mq->mqrq_prev->req) >> - /* claim host only for the first request */ >> - mmc_get_card(card); >> + mmc_get_card(card); >> >> ret = mmc_blk_part_switch(card, md); >> if (ret) { >> @@ -2190,15 +2188,8 @@ static int mmc_blk_issue_rq(struct mmc_queue *mq, >> struct request *req) >> } >> >> out: >> - if ((!req && !(mq->flags & MMC_QUEUE_NEW_REQUEST)) || >> - mmc_req_is_special(req)) >> - /* >> - * Release host when there are no more requests >> - * and after special request(discard, flush) is done. >> - * In case sepecial request, there is no reentry to >> - * the 'mmc_blk_issue_rq' with 'mqrq_prev->req'. >> - */ >> - mmc_put_card(card); >> + mmc_put_card(card); >> + >> return ret; >> } >> >> >> Which fixes this, further pointing to the somewhat magical claim / release >> code in mmc_blk_issue_rq() being the culprit. >> >> Looking at recent commits these 2 stand out as possible causes of this: >> >> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=c2df40dfb8c015211ec55f4b1dd0587f875c7b34 >> >> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=3a5e02ced11e22ecd9da3d6710afe15bcfee1d10 >> >> >> I've the feeling that one of these is making mmc_blk_issue_rq() not >> claiming >> the host while it should do so ... >> > > There is a bug with those patches and the secure discard ones where when > REQ_OP_SECURE_ERASE is sent, mmc_put_card above will not be called, and > they will be treated as normal requests instead of special one so the > drivers lists are not executed properly. Actually the problem seems to be mmc_get_card not getting called while it should at the top of mmc_blk_issue_rq, I first get a WARN_ON(!host->claimed) triggering in mmc_start_request (so missing mmc_card_get) and then in mmc_release_host (mmc_card_put called without mc_card_get being called first). > The patch in Jens's tree > https://git.kernel.org/cgit/linux/kernel/git/axboe/linux-block.git/commit/?h=for-linus&id=7afafc8a44bf0ab841b17d450b02aedb3a138985 > fixes the issue. I've tried 4.8-rc3 with my hack drop and this commit cherry-picked, but the problem is still there, so this patch does not fix it. Regards, Hans