linux-ext4 - Re: [PATCH v11 4/5] f2fs: support direct I/O with fscrypt using blk-crypto

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Date:   Fri, 28 Jan 2022 16:27:43 -0800
From:   Jaegeuk Kim <jaegeuk@...nel.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, Theodore Ts'o <tytso@....edu>,
        Christoph Hellwig <hch@....de>,
        "Darrick J . Wong" <djwong@...nel.org>,
        Dave Chinner <david@...morbit.com>,
        Satya Tangirala <satyat@...gle.com>
Subject: Re: [PATCH v11 4/5] f2fs: support direct I/O with fscrypt using
 blk-crypto

On 01/28, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@...gle.com>
> 
> Encrypted files traditionally haven't supported DIO, due to the need to
> encrypt/decrypt the data.  However, when the encryption is implemented
> using inline encryption (blk-crypto) instead of the traditional
> filesystem-layer encryption, it is straightforward to support DIO.
> 
> Therefore, make f2fs support DIO on files that are using inline
> encryption.  Since f2fs uses iomap for DIO, and fscrypt support was
> already added to iomap DIO, this just requires two small changes:
> 
> - Let DIO proceed when supported, by checking fscrypt_dio_supported()
>   instead of assuming that encrypted files never support DIO.
> 
> - In f2fs_iomap_begin(), use fscrypt_limit_io_blocks() to limit the
>   length of the mapping in the rare case where a DUN discontiguity
>   occurs in the middle of an extent.  The iomap DIO implementation
>   requires this, since it assumes that it can submit a bio covering (up
>   to) the whole mapping, without checking fscrypt constraints itself.
> 
> Co-developed-by: Satya Tangirala <satyat@...gle.com>
> Signed-off-by: Satya Tangirala <satyat@...gle.com>
> Signed-off-by: Eric Biggers <ebiggers@...gle.com>

Acked-by: Jaegeuk Kim <jaegeuk@...nel.org>

> ---
>  fs/f2fs/data.c | 7 +++++++
>  fs/f2fs/f2fs.h | 6 +++++-
>  2 files changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 8c417864c66ae..020d47f97969c 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -4044,6 +4044,13 @@ static int f2fs_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
>  
>  	iomap->offset = blks_to_bytes(inode, map.m_lblk);
>  
> +	/*
> +	 * When inline encryption is enabled, sometimes I/O to an encrypted file
> +	 * has to be broken up to guarantee DUN contiguity.  Handle this by
> +	 * limiting the length of the mapping returned.
> +	 */
> +	map.m_len = fscrypt_limit_io_blocks(inode, map.m_lblk, map.m_len);
> +
>  	if (map.m_flags & (F2FS_MAP_MAPPED | F2FS_MAP_UNWRITTEN)) {
>  		iomap->length = blks_to_bytes(inode, map.m_len);
>  		if (map.m_flags & F2FS_MAP_MAPPED) {
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index eb22fa91c2b26..db46f3cf0885d 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -4371,7 +4371,11 @@ static inline bool f2fs_force_buffered_io(struct inode *inode,
>  	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
>  	int rw = iov_iter_rw(iter);
>  
> -	if (f2fs_post_read_required(inode))
> +	if (!fscrypt_dio_supported(iocb, iter))
> +		return true;
> +	if (fsverity_active(inode))
> +		return true;
> +	if (f2fs_compressed_file(inode))
>  		return true;
>  
>  	/* disallow direct IO if any of devices has unaligned blksize */
> -- 
> 2.35.0