linux-ext4 - Re: [PATCH v6 4/5] dm-thin: Add REQ_OP

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Date:   Mon, 15 May 2023 14:19:20 -0700
From:   Sarthak Kukreti <sarthakkukreti@...omium.org>
To:     Mike Snitzer <snitzer@...nel.org>
Cc:     dm-devel@...hat.com, linux-block@...r.kernel.org,
        linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, Jens Axboe <axboe@...nel.dk>,
        "Theodore Ts'o" <tytso@....edu>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        "Darrick J. Wong" <djwong@...nel.org>,
        Jason Wang <jasowang@...hat.com>,
        Bart Van Assche <bvanassche@...gle.com>,
        Christoph Hellwig <hch@...radead.org>,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        Stefan Hajnoczi <stefanha@...hat.com>,
        Brian Foster <bfoster@...hat.com>,
        Alasdair Kergon <agk@...hat.com>
Subject: Re: [PATCH v6 4/5] dm-thin: Add REQ_OP_PROVISION support

On Fri, May 12, 2023 at 10:32 AM Mike Snitzer <snitzer@...nel.org> wrote:
>
> On Sat, May 06 2023 at  2:29P -0400,
> Sarthak Kukreti <sarthakkukreti@...omium.org> wrote:
>
> > dm-thinpool uses the provision request to provision
> > blocks for a dm-thin device. dm-thinpool currently does not
> > pass through REQ_OP_PROVISION to underlying devices.
> >
> > For shared blocks, provision requests will break sharing and copy the
> > contents of the entire block. Additionally, if 'skip_block_zeroing'
> > is not set, dm-thin will opt to zero out the entire range as a part
> > of provisioning.
> >
> > Signed-off-by: Sarthak Kukreti <sarthakkukreti@...omium.org>
> > ---
> >  drivers/md/dm-thin.c | 70 +++++++++++++++++++++++++++++++++++++++++---
> >  1 file changed, 66 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
> > index 2b13c949bd72..3f94f53ac956 100644
> > --- a/drivers/md/dm-thin.c
> > +++ b/drivers/md/dm-thin.c
> ...
> > @@ -4114,6 +4171,8 @@ static void pool_io_hints(struct dm_target *ti, struct queue_limits *limits)
> >        * The pool uses the same discard limits as the underlying data
> >        * device.  DM core has already set this up.
> >        */
> > +
> > +     limits->max_provision_sectors = pool->sectors_per_block;
>
> Just noticed that setting limits->max_provision_sectors needs to move
> above pool_io_hints code that sets up discards -- otherwise the early
> return from if (!pt->adjusted_pf.discard_enabled) will cause setting
> max_provision_sectors to be skipped.
>
> Here is a roll up of the fixes that need to be folded into this patch:
>
Ah right, thanks for pointing that out! I'll fold this into v7.

Best
Sarthak

> diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
> index 3f94f53ac956..90c8e36cb327 100644
> --- a/drivers/md/dm-thin.c
> +++ b/drivers/md/dm-thin.c
> @@ -4151,6 +4151,8 @@ static void pool_io_hints(struct dm_target *ti, struct queue_limits *limits)
>                 blk_limits_io_opt(limits, pool->sectors_per_block << SECTOR_SHIFT);
>         }
>
> +       limits->max_provision_sectors = pool->sectors_per_block;
> +
>         /*
>          * pt->adjusted_pf is a staging area for the actual features to use.
>          * They get transferred to the live pool in bind_control_target()
> @@ -4171,8 +4173,6 @@ static void pool_io_hints(struct dm_target *ti, struct queue_limits *limits)
>          * The pool uses the same discard limits as the underlying data
>          * device.  DM core has already set this up.
>          */
> -
> -       limits->max_provision_sectors = pool->sectors_per_block;
>  }
>
>  static struct target_type pool_target = {
> @@ -4349,6 +4349,7 @@ static int thin_ctr(struct dm_target *ti, unsigned int argc, char **argv)
>
>         ti->num_provision_bios = 1;
>         ti->provision_supported = true;
> +       ti->max_provision_granularity = true;
>
>         mutex_unlock(&dm_thin_pool_table.mutex);
>