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From: Bart Van Assche <bvanassche@acm.org>
To: Satya Tangirala <satyat@google.com>
Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
	Jens Axboe <axboe@kernel.dk>, Eric Biggers <ebiggers@google.com>
Subject: Re: [PATCH v2 0/8] ensure bios aren't split in middle of crypto data unit
Date: Thu, 25 Mar 2021 20:46:20 -0700	[thread overview]
Message-ID: <4694766c-8d95-1ad3-cb0c-d1ba8b7fe7ad@acm.org> (raw)
In-Reply-To: <YF07bqQ1NvPxPNrh@google.com>

On 3/25/21 6:39 PM, Satya Tangirala wrote:
> On Thu, Mar 25, 2021 at 02:51:31PM -0700, Bart Van Assche wrote:
>> Are you sure that the block layer core splits bios at logical block
>> boundaries? Commit 9cc5169cd478 ("block: Improve physical block
>> alignment of split bios") should have changed the behavior from
>> splitting at logical block boundaries into splitting at physical block
>> boundaries.
>
> Ah, what I really meant with that sentence was "Currently, if a bio is
> split, the size of the resulting bio is guaranteed to be aligned to a
> the lbs. The endpoint of the bio might also be aligned to a physical
> block boundary (which 9cc5169cd478 tries to achieve if possible), but
> the bio's size (and hence also its endpoint since the start of the bio
> is always lbs aligned) is *at least* lbs aligned". Does that sound
> accurate?
That sounds better to me :-)

>> Without having looked at this patch series, can the same
>> effect be achieved by reporting the crypto data unit size as the
>> physical block size?
>
> That would've been awesome, but I don't think we can do that :(
> 1) There isn't only one crypto data unit size. A device can support,
>    and upper layers are free to use, many different data unit sizes.
> 2) IIUC 9cc5169cd478 (or more accurately get_max_io_size() since the
>    function has been changed slightly since your original patch)
>    doesn't align the size of the bio to the pbs - it only aligns the
>    endpoint of the bio to the pbs (and it may actually not even do
>    that if it turns out to not be possible). Is that right? If so,
>    that means that if the startpoint of the bio isn't pbs aligned, the
>    size of the bio won't be pbs aligned either.

Hmm ... if the start of a bio is not aligned to the physical block size
I don't think that the block layer can do anything about the start of
the bio. Anyway, I have taken a quick look at this patch series and the
patch series looks pretty clean to me. I will let Christoph review this
patch series since he already reviewed the previous version of this series.

Bart.

  reply	other threads:[~2021-03-26  3:47 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-25 21:26 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
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 [this message]
2021-03-26  7:56       ` Satya Tangirala

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