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From: Eric Biggers <ebiggers@kernel.org>
To: Satya Tangirala <satyat@google.com>
Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
	Jens Axboe <axboe@kernel.dk>
Subject: Re: [PATCH v2 4/8] block: introduce bio_required_sector_alignment()
Date: Thu, 15 Apr 2021 12:44:30 -0700	[thread overview]
Message-ID: <YHiXns+jQL+MrmNK@gmail.com> (raw)
In-Reply-To: <20210325212609.492188-5-satyat@google.com>

On Thu, Mar 25, 2021 at 09:26:05PM +0000, Satya Tangirala wrote:
> This function returns the required alignment for the number of sectors in
> a bio. In particular, the number of sectors passed to bio_split() must be
> aligned to this value.
> 
> Signed-off-by: Satya Tangirala <satyat@google.com>
> ---
>  block/blk.h | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/block/blk.h b/block/blk.h
> index 3b53e44b967e..5ef207a6d34c 100644
> --- a/block/blk.h
> +++ b/block/blk.h
> @@ -261,6 +261,18 @@ static inline unsigned int bio_allowed_max_sectors(struct request_queue *q)
>  	return round_down(UINT_MAX, queue_logical_block_size(q)) >> 9;
>  }
>  
> +/*
> + * The required sector alignment for a bio. The number of sectors in any bio
> + * that's constructed/split must be aligned to this value.

What does "constructed" mean in this context?

> + */
> +static inline unsigned int bio_required_sector_alignment(struct bio *bio)
> +{
> +	struct request_queue *q = bio->bi_bdev->bd_disk->queue;
> +
> +	return max(queue_logical_block_size(q) >> SECTOR_SHIFT,
> +		   blk_crypto_bio_sectors_alignment(bio));
> +}

It would be slightly simpler to use bdev_logical_block_size(bio->bi_bdev)
instead of queue_logical_block_size(bio->bi_bdev->bd_disk->queue).

Also, if there's interest in avoiding the branch implied by the max() here, it
would be possible to take advantage of the values being powers of 2 as follows:

static inline unsigned int bio_required_sector_alignment(struct bio *bio)
{
	unsigned int alignmask =
		(bdev_logical_block_size(q) >> SECTOR_SHIFT) - 1;

	alignmask |= blk_crypto_bio_sectors_alignment(bio) - 1;

	return alignmask + 1;
}

  parent reply	other threads:[~2021-04-15 19:44 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-25 21:26 [PATCH v2 0/8] ensure bios aren't split in middle of crypto data unit Satya Tangirala
2021-03-25 21:26 ` [PATCH v2 1/8] block: introduce blk_ksm_is_empty() Satya Tangirala
2021-03-30 18:04   ` Christoph Hellwig
2021-04-15 19:21   ` Eric Biggers
2021-03-25 21:26 ` [PATCH v2 2/8] dm,mmc,ufshcd: handle error from blk_ksm_register() Satya Tangirala
2021-04-15 19:27   ` Eric Biggers
2021-03-25 21:26 ` [PATCH v2 3/8] block: blk-crypto: introduce blk_crypto_bio_sectors_alignment() Satya Tangirala
2021-04-15 19:33   ` Eric Biggers
2021-03-25 21:26 ` [PATCH v2 4/8] block: introduce bio_required_sector_alignment() Satya Tangirala
2021-03-30 18:06   ` Christoph Hellwig
2021-04-15 19:37     ` Eric Biggers
2021-04-15 19:44   ` Eric Biggers [this message]
2021-03-25 21:26 ` [PATCH v2 5/8] block: respect bio_required_sector_alignment() in blk-crypto-fallback Satya Tangirala
2021-04-15 19:45   ` Eric Biggers
2021-03-25 21:26 ` [PATCH v2 6/8] block: keyslot-manager: introduce blk_ksm_restrict_dus_to_queue_limits() Satya Tangirala
2021-03-26  3:50   ` kernel test robot
2021-03-26  6:28   ` kernel test robot
2021-04-15 19:55   ` Eric Biggers
2021-03-25 21:26 ` [PATCH v2 7/8] blk-merge: Ensure bios aren't split in middle of a crypto data unit Satya Tangirala
2021-03-25 21:26 ` [PATCH v2 8/8] block: add WARN() in bio_split() for sector alignment Satya Tangirala
2021-03-26  3:47   ` Bart Van Assche
2021-04-15 20:00   ` Eric Biggers
2021-03-25 21:51 ` [PATCH v2 0/8] ensure bios aren't split in middle of crypto data unit Bart Van Assche
2021-03-26  1:39   ` Satya Tangirala
2021-03-26  3:46     ` Bart Van Assche
2021-03-26  7:56       ` Satya Tangirala

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