linux-ext4 - Re: [PATCH v10 1/5] fscrypt: add functions for direct I/O support

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Date:   Thu, 20 Jan 2022 00:27:45 -0800
From:   Christoph Hellwig <hch@...radead.org>
To:     Eric Biggers <ebiggers@...nel.org>
Cc:     linux-fscrypt@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-ext4@...r.kernel.org, linux-f2fs-devel@...ts.sourceforge.net,
        linux-xfs@...r.kernel.org, Christoph Hellwig <hch@...radead.org>,
        Dave Chinner <david@...morbit.com>,
        "Darrick J . Wong" <djwong@...nel.org>,
        Theodore Ts'o <tytso@....edu>,
        Jaegeuk Kim <jaegeuk@...nel.org>, Chao Yu <chao@...nel.org>,
        Satya Tangirala <satyat@...gle.com>
Subject: Re: [PATCH v10 1/5] fscrypt: add functions for direct I/O support

> +/**
> + * fscrypt_dio_unsupported() - check whether a DIO (direct I/O) request is
> + *			       unsupported due to encryption constraints
> + * @iocb: the file and position the I/O is targeting
> + * @iter: the I/O data segment(s)
> + *
> + * Return: true if DIO is unsupported
> + */
> +bool fscrypt_dio_unsupported(struct kiocb *iocb, struct iov_iter *iter)

I always find non-negated functions easier to follow, i.e. turn this
into fscrypt_dio_supported().

> +	/*
> +	 * Since the granularity of encryption is filesystem blocks, the file
> +	 * position and total I/O length must be aligned to the filesystem block
> +	 * size -- not just to the block device's logical block size as is
> +	 * traditionally the case for DIO on many filesystems (not including
> +	 * f2fs, which only allows filesystem block aligned DIO anyway).

I would not really mention a specific file system here.