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Date:   Fri, 23 Sep 2022 11:15:05 -0400
From:   Mike Snitzer <snitzer@redhat.com>
To:     Sarthak Kukreti <sarthakkukreti@chromium.org>
Cc:     dm-devel@redhat.com, linux-block@vger.kernel.org,
        linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org,
        virtualization@lists.linux-foundation.org,
        Jens Axboe <axboe@kernel.dk>,
        "Michael S . Tsirkin" <mst@redhat.com>,
        Jason Wang <jasowang@redhat.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Stefan Hajnoczi <stefanha@redhat.com>,
        Alasdair Kergon <agk@redhat.com>,
        Mike Snitzer <snitzer@kernel.org>,
        Theodore Ts'o <tytso@mit.edu>,
        Andreas Dilger <adilger.kernel@dilger.ca>,
        Bart Van Assche <bvanassche@google.com>,
        Daniil Lunev <dlunev@google.com>,
        Evan Green <evgreen@google.com>,
        Gwendal Grignou <gwendal@google.com>
Subject: Re: [PATCH RFC 1/8] block: Introduce provisioning primitives
Message-ID: <Yy3NeY02zEMLTdsa@redhat.com>
References: <20220915164826.1396245-1-sarthakkukreti@google.com>
 <20220915164826.1396245-2-sarthakkukreti@google.com>
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On Thu, Sep 15 2022 at 12:48P -0400,
Sarthak Kukreti <sarthakkukreti@chromium.org> wrote:

> From: Sarthak Kukreti <sarthakkukreti@chromium.org>
> 
> Introduce block request REQ_OP_PROVISION. The intent of this request
> is to request underlying storage to preallocate disk space for the given
> block range. Block device that support this capability will export
> a provision limit within their request queues.
> 
> Signed-off-by: Sarthak Kukreti <sarthakkukreti@chromium.org>
> ---
>  block/blk-core.c          |  5 ++++
>  block/blk-lib.c           | 55 +++++++++++++++++++++++++++++++++++++++
>  block/blk-merge.c         | 17 ++++++++++++
>  block/blk-settings.c      | 19 ++++++++++++++
>  block/blk-sysfs.c         |  8 ++++++
>  block/bounce.c            |  1 +
>  include/linux/bio.h       |  6 +++--
>  include/linux/blk_types.h |  5 +++-
>  include/linux/blkdev.h    | 16 ++++++++++++
>  9 files changed, 129 insertions(+), 3 deletions(-)
> 
> diff --git a/block/blk-settings.c b/block/blk-settings.c
> index 8bb9eef5310e..be79ad68b330 100644
> --- a/block/blk-settings.c
> +++ b/block/blk-settings.c
> @@ -57,6 +57,7 @@ void blk_set_default_limits(struct queue_limits *lim)
>  	lim->misaligned = 0;
>  	lim->zoned = BLK_ZONED_NONE;
>  	lim->zone_write_granularity = 0;
> +	lim->max_provision_sectors = 0;
>  }
>  EXPORT_SYMBOL(blk_set_default_limits);
>  
> @@ -81,6 +82,7 @@ void blk_set_stacking_limits(struct queue_limits *lim)
>  	lim->max_dev_sectors = UINT_MAX;
>  	lim->max_write_zeroes_sectors = UINT_MAX;
>  	lim->max_zone_append_sectors = UINT_MAX;
> +	lim->max_provision_sectors = UINT_MAX;
>  }
>  EXPORT_SYMBOL(blk_set_stacking_limits);
>  

Please work through the blk_stack_limits() implementation too (simple
min_not_zero?).