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From: Christoph Hellwig <hch@infradead.org>
To: Satya Tangirala <satyaprateek2357@gmail.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 v4 0/9] ensure bios aren't split in middle of crypto data unit
Date: Sat, 24 Jul 2021 08:36:52 +0100	[thread overview]
Message-ID: <YPvDFH7uAP+Jas/X@infradead.org> (raw)
In-Reply-To: <20210707052943.3960-1-satyaprateek2357@gmail.com>

On Tue, Jul 06, 2021 at 10:29:34PM -0700, Satya Tangirala wrote:
> When a bio has an encryption context, its size must be aligned to its
> crypto data unit size. A bio must not be split in the middle of a data
> unit. Currently, bios are split at logical block boundaries, but a crypto
> data unit size might be larger than the logical block size - e.g. a machine
> could be using fscrypt (which uses 4K crypto data units) with an eMMC block
> device with inline encryption hardware that has a logical block size of 512
> bytes.
> 
> Right now, the only user of blk-crypto is fscrypt (on ext4 and f2fs), which
> (currently) only submits bios where the size of each segment is a multiple
> of data_unit_size.  That happens to avoid most of the cases where bios
> could be split in the middle of a data unit.  However, when support for
> direct I/O on encrypted files is added, or when support for filesystem
> metadata encryption is added, it will be possible for bios to have segment
> lengths that are multiples of the logical block size, but not multiples of
> the crypto data unit size.  So the block layer needs to start handling this
> case appropriately.

I'm still not sold on this case yet.  sector size aligned I/O is an
optional feature, and I don't think it is worth this overhead.  And
while file systems metadata can be smaller than the file system block
size in a few cases (e.g. XFS log writes), that is usually an extra
performance optimization and can be trivially disabled in mkfs.

      parent reply	other threads:[~2021-07-24  7:37 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-07  5:29 [PATCH v4 0/9] ensure bios aren't split in middle of crypto data unit Satya Tangirala
2021-07-07  5:29 ` [PATCH v4 1/9] block: introduce blk_ksm_is_empty() Satya Tangirala
2021-07-23 16:45   ` Eric Biggers
2021-07-07  5:29 ` [PATCH v4 2/9] block: blk-crypto: introduce blk_crypto_bio_sectors_alignment() Satya Tangirala
2021-07-23 16:45   ` Eric Biggers
2021-07-07  5:29 ` [PATCH v4 3/9] block: introduce bio_required_sector_alignment() Satya Tangirala
2021-07-23 16:46   ` Eric Biggers
2021-07-07  5:29 ` [PATCH v4 4/9] block: keyslot-manager: introduce blk_ksm_restrict_dus_to_queue_limits() Satya Tangirala
2021-07-23 17:08   ` Eric Biggers
2021-07-07  5:29 ` [PATCH v4 5/9] ufshcd: handle error from blk_ksm_register() Satya Tangirala
2021-07-23 17:13   ` Eric Biggers
2021-07-07  5:29 ` [PATCH v4 6/9] mmc: " Satya Tangirala
2021-07-07  5:29 ` [PATCH v4 7/9] dm: " Satya Tangirala
2021-07-23 17:26   ` Eric Biggers
2021-07-07  5:29 ` [PATCH v4 8/9] blk-merge: Ensure bios aren't split in middle of a crypto data unit Satya Tangirala
2021-07-23 18:11   ` Eric Biggers
2021-07-07  5:29 ` [PATCH v4 9/9] block: add WARN_ON_ONCE() to bio_split() for sector alignment Satya Tangirala
2021-07-23 17:30   ` Eric Biggers
2021-07-23 16:49 ` [PATCH v4 0/9] ensure bios aren't split in middle of crypto data unit Eric Biggers
2021-07-23 17:52   ` Eric Biggers
2021-07-24  7:36 ` Christoph Hellwig [this message]

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