From: Mike Christie Subject: Re: [PATCH 37/45] drivers: use req op accessor Date: Thu, 4 Aug 2016 00:47:03 -0500 Message-ID: <57A2D6D7.8040807@redhat.com> References: <1465155145-10812-1-git-send-email-mchristi@redhat.com> <1465155145-10812-38-git-send-email-mchristi@redhat.com> <87fbe31f-27b3-ff7a-e381-34fc1aad337e@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Cc: Ross Zwisler , Ross Zwisler , Dave Chinner , Jens Axboe , linux-f2fs-devel@lists.sourceforge.net, linux-ext4 , konrad.wilk@oracle.com, drbd-dev@lists.linbit.com, philipp.reisner@linbit.com, lars.ellenberg@linbit.com, linux-raid@vger.kernel.org, dm-devel@redhat.com, linux-fsdevel , linux-bcache@vger.kernel.org, linux-block@vger.kernel.org, LKML , linux-scsi@vger.kernel.org, linux-mtd@lists.infradead.org, target-devel@vger.kernel.org, linux-btrfs@vger.kernel.org, osd-dev@open-osd.org, XFS Developers , ocfs2-devel@oss.oracle.com To: Shaun Tancheff Return-path: In-Reply-To: Sender: linux-bcache-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org On 08/03/2016 07:30 PM, Shaun Tancheff wrote: > On Wed, Aug 3, 2016 at 6:47 PM, Mike Christie wrote: >> On 08/03/2016 05:33 PM, Ross Zwisler wrote: >>> On Sun, Jun 5, 2016 at 1:32 PM, wrote: >>>> From: Mike Christie >>>> >>>> The req operation REQ_OP is separated from the rq_flag_bits >>>> definition. This converts the block layer drivers to >>>> use req_op to get the op from the request struct. >>>> >>>> Signed-off-by: Mike Christie >>>> --- >>>> drivers/block/loop.c | 6 +++--- >>>> drivers/block/mtip32xx/mtip32xx.c | 2 +- >>>> drivers/block/nbd.c | 2 +- >>>> drivers/block/rbd.c | 4 ++-- >>>> drivers/block/xen-blkfront.c | 8 +++++--- >>>> drivers/ide/ide-floppy.c | 2 +- >>>> drivers/md/dm.c | 2 +- >>>> drivers/mmc/card/block.c | 7 +++---- >>>> drivers/mmc/card/queue.c | 6 ++---- >>> >>> Dave Chinner reported a deadlock with XFS + DAX, which I reproduced >>> and bisected to this commit: >>> >>> commit c2df40dfb8c015211ec55f4b1dd0587f875c7b34 >>> Author: Mike Christie >>> Date: Sun Jun 5 14:32:17 2016 -0500 >>> drivers: use req op accessor >>> >>> Here are the steps to reproduce the deadlock with a BRD ramdisk: >>> >>> mkfs.xfs -f /dev/ram0 >>> mount -o dax /dev/ram0 /mnt/scratch >> >> When using ramdisks, we need the attached patch like in your other bug >> report. I think it will fix some hangs people are seeing. >> >> I do not think that it should cause the failure to run issue you saw >> when doing generic/008 and ext2. >> > > I think the translation in loop.c is suspicious here: > > "if use DIO && not (a flush_flag or discard_flag)" > should translate to: > "if use DIO && not ((a flush_flag) || op == discard)" > > But in the patch I read: > "if use DIO && ((not a flush_flag) || op == discard) > > Which would have DIO && discards follow the AIO path? > > So I would humbly suggest something like the following > (on top of commit c2df40dfb8c015211ec55f4b1dd0587f875c7b34): > [Please excuse the messed up patch format ... gmail eats tabs] > > diff --git a/drivers/block/loop.c b/drivers/block/loop.c > index b9b737c..0754d83 100644 > --- a/drivers/block/loop.c > +++ b/drivers/block/loop.c > @@ -1659,8 +1659,9 @@ static int loop_queue_rq(struct blk_mq_hw_ctx *hctx, > if (lo->lo_state != Lo_bound) > return -EIO; > > - if (lo->use_dio && (!(cmd->rq->cmd_flags & REQ_FLUSH) || > - req_op(cmd->rq) == REQ_OP_DISCARD)) > + if (lo->use_dio && !( > + (cmd->rq->cmd_flags & REQ_FLUSH) || > + req_op(cmd->rq) == REQ_OP_DISCARD)) > cmd->use_aio = true; > else > cmd->use_aio = false; > You are right. The translation was bad and your code above is correct. I think we need my patch in the other mail though too, because for the rw_page user case if WB_SYNC_ALL is set, then the IO gets sent down as a read instead of a write.