linux-ext4 - Re: [PATCH v7 6/8] ext4: support direct I/O with fscrypt using blk-crypto

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Date:   Thu, 3 Dec 2020 08:45:39 -0500
From:   "Theodore Y. Ts'o" <tytso@....edu>
To:     Satya Tangirala <satyat@...gle.com>
Cc:     Jaegeuk Kim <jaegeuk@...nel.org>,
        Eric Biggers <ebiggers@...nel.org>, Chao Yu <chao@...nel.org>,
        Jens Axboe <axboe@...nel.dk>,
        "Darrick J . Wong" <darrick.wong@...cle.com>,
        linux-kernel@...r.kernel.org, linux-fscrypt@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net, linux-xfs@...r.kernel.org,
        linux-block@...r.kernel.org, linux-ext4@...r.kernel.org,
        Eric Biggers <ebiggers@...gle.com>
Subject: Re: [PATCH v7 6/8] ext4: support direct I/O with fscrypt using
 blk-crypto

On Tue, Nov 17, 2020 at 02:07:06PM +0000, Satya Tangirala wrote:
> From: Eric Biggers <ebiggers@...gle.com>
> 
> Wire up ext4 with fscrypt direct I/O support. Direct I/O with fscrypt is
> only supported through blk-crypto (i.e. CONFIG_BLK_INLINE_ENCRYPTION must
> have been enabled, the 'inlinecrypt' mount option must have been specified,
> and either hardware inline encryption support must be present or
> CONFIG_BLK_INLINE_ENCYRPTION_FALLBACK must have been enabled). Further,
> direct I/O on encrypted files is only supported when the *length* of the
> I/O is aligned to the filesystem block size (which is *not* necessarily the
> same as the block device's block size).
> 
> fscrypt_limit_io_blocks() is called before setting up the iomap to ensure
> that the blocks of each bio that iomap will submit will have contiguous
> DUNs. Note that fscrypt_limit_io_blocks() is normally a no-op, as normally
> the DUNs simply increment along with the logical blocks. But it's needed
> to handle an edge case in one of the fscrypt IV generation methods.
> 
> Signed-off-by: Eric Biggers <ebiggers@...gle.com>
> Co-developed-by: Satya Tangirala <satyat@...gle.com>
> Signed-off-by: Satya Tangirala <satyat@...gle.com>
> Reviewed-by: Jaegeuk Kim <jaegeuk@...nel.org>

Acked-by: Theodore Ts'o <tytso@....edu>