Linux-FSCrypt Archive on lore.kernel.org
 help / color / Atom feed
From: Dave Chinner <david@fromorbit.com>
To: Eric Biggers <ebiggers@kernel.org>
Cc: Satya Tangirala <satyat@google.com>,
	linux-fscrypt@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	linux-f2fs-devel@lists.sourceforge.net,
	linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org
Subject: Re: [PATCH v4 3/7] iomap: support direct I/O with fscrypt using blk-crypto
Date: Sun, 26 Jul 2020 09:59:53 +1000
Message-ID: <20200725235953.GS2005@dread.disaster.area> (raw)
In-Reply-To: <20200725234751.GR2005@dread.disaster.area>

On Sun, Jul 26, 2020 at 09:47:51AM +1000, Dave Chinner wrote:
> On Fri, Jul 24, 2020 at 10:41:32AM -0700, Eric Biggers wrote:
> > But again, as far as I can tell, fs/iomap/direct-io.c currently *does* guarantee
> > that *if* the input is fully filesystem-block-aligned and if blocksize <=
> > PAGE_SIZE, then the issued I/O is also filesystem-block-aligned.
> 
> Please listen to what I'm saying, Eric.
> 
> The -current iomap implementation- may provide that behaviour. That
> doesn't mean we guarantee that behaviour. i.e. the iomap -design-
> does not guaranteee that behaviour, and we don't guarantee such
> behaviour into the future. And we won't guarantee this behaviour -
> even though the current implementation may provide it - because the
> rest of the IO stack below iomap does not provide iomap with that
> guarantee.
> 
> Hence if iomap cannot get a guarantee that IO it issues won't get
> split at some arbitrary boundary, it cannot provide filesystems with
> that guarantee.

BTW, if you want iomap_dio_rw() to provide an arbitrary bio
alignment guarantee at the iomap layer, then it should be returned
in the iomap along with the extent mapping. That could then be used
instead of the bdev logical block size. That won't guarantee the
behaviour of the rest of the stack, but it would provide a defined
IO submission behaviour that iomap would have to guarantee into the
future...

That would also remove the need to duplicate the alignment checks
in the filesystem for fscrypt DIO...

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

  reply index

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-20 23:37 [PATCH v4 0/7] add support for " Satya Tangirala
2020-07-20 23:37 ` [PATCH v4 1/7] fscrypt: Add functions for direct I/O support Satya Tangirala
2020-07-22 17:04   ` Jaegeuk Kim
2020-07-20 23:37 ` [PATCH v4 2/7] direct-io: add support for fscrypt using blk-crypto Satya Tangirala
2020-07-22 17:05   ` Jaegeuk Kim
2020-07-20 23:37 ` [PATCH v4 3/7] iomap: support direct I/O with " Satya Tangirala
2020-07-22 17:06   ` Jaegeuk Kim
2020-07-22 21:16   ` Dave Chinner
2020-07-22 22:34     ` Eric Biggers
2020-07-22 22:44       ` Matthew Wilcox
2020-07-22 23:12         ` Eric Biggers
2020-07-22 23:26       ` Eric Biggers
2020-07-22 23:32         ` Darrick J. Wong
2020-07-22 23:43           ` Eric Biggers
2020-07-23 22:07       ` Dave Chinner
2020-07-23 23:03         ` Eric Biggers
2020-07-24  1:39           ` Dave Chinner
2020-07-24  3:46             ` Eric Biggers
2020-07-24  5:31               ` Dave Chinner
2020-07-24 17:41                 ` Eric Biggers
2020-07-25 23:47                   ` Dave Chinner
2020-07-25 23:59                     ` Dave Chinner [this message]
2020-07-26  2:42                     ` Eric Biggers
2020-07-27 17:16                       ` Eric Biggers
2020-07-20 23:37 ` [PATCH v4 4/7] ext4: " Satya Tangirala
2020-07-22 17:07   ` Jaegeuk Kim
2020-07-20 23:37 ` [PATCH v4 5/7] f2fs: " Satya Tangirala
2020-07-21 20:11   ` Jaegeuk Kim
2020-07-20 23:37 ` [PATCH v4 6/7] fscrypt: document inline encryption support Satya Tangirala
2020-07-22 17:01   ` Jaegeuk Kim
2020-07-20 23:37 ` [PATCH v4 7/7] fscrypt: update documentation for direct I/O support Satya Tangirala
2020-07-21  0:47   ` Eric Biggers
2020-07-22 16:57     ` Jaegeuk Kim
2020-07-21  0:56 ` [PATCH v4 0/7] add support for direct I/O with fscrypt using blk-crypto Eric Biggers

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20200725235953.GS2005@dread.disaster.area \
    --to=david@fromorbit.com \
    --cc=ebiggers@kernel.org \
    --cc=linux-ext4@vger.kernel.org \
    --cc=linux-f2fs-devel@lists.sourceforge.net \
    --cc=linux-fscrypt@vger.kernel.org \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=linux-xfs@vger.kernel.org \
    --cc=satyat@google.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-FSCrypt Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-fscrypt/0 linux-fscrypt/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-fscrypt linux-fscrypt/ https://lore.kernel.org/linux-fscrypt \
		linux-fscrypt@vger.kernel.org
	public-inbox-index linux-fscrypt

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-fscrypt


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git