| Message ID | CAJVOszAd9Eu88P2=QoNVArd0jwDH7KRe=OB82tCNMpjfv9B4KA@mail.gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 08/03/2016 07:30 PM, Shaun Tancheff wrote: > On Wed, Aug 3, 2016 at 6:47 PM, Mike Christie <mchristi@redhat.com> wrote: >> On 08/03/2016 05:33 PM, Ross Zwisler wrote: >>> On Sun, Jun 5, 2016 at 1:32 PM, <mchristi@redhat.com> wrote: >>>> From: Mike Christie <mchristi@redhat.com> >>>> >>>> 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 <mchristi@redhat.com> >>>> --- >>>> 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 <mchristi@redhat.com> >>> 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.
On Wed, Aug 03, 2016 at 07:30:29PM -0500, Shaun Tancheff wrote: > 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? Indeed. Sorry for missing out on your patch, I just sent a fix in reply to Dave's other report earlier which is pretty similar to yours.
On Thu, Aug 4, 2016 at 10:46 AM, Christoph Hellwig <hch@infradead.org> wrote: > On Wed, Aug 03, 2016 at 07:30:29PM -0500, Shaun Tancheff wrote: >> 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? > > Indeed. Sorry for missing out on your patch, I just sent a fix > in reply to Dave's other report earlier which is pretty similar to > yours. No worries. I prefer your switch to a an if conditional here.
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;