Re: [PATCH v7 9/9] ext4: add inline encryption support

[Eric Biggers <ebiggers@kernel.org>]

On Fri, Feb 21, 2020 at 03:50:50AM -0800, Satya Tangirala wrote:
> From: Eric Biggers <ebiggers@google.com>
> 
> Wire up ext4 to support inline encryption via the helper functions which
> fs/crypto/ now provides.  This includes:
> 
> - Adding a mount option 'inlinecrypt' which enables inline encryption
>   on encrypted files where it can be used.
> 
> - Setting the bio_crypt_ctx on bios that will be submitted to an
>   inline-encrypted file.
> 
>   Note: submit_bh_wbc() in fs/buffer.c also needed to be patched for
>   this part, since ext4 sometimes uses ll_rw_block() on file data.
> 
> - Not adding logically discontiguous data to bios that will be submitted
>   to an inline-encrypted file.
> 
> - Not doing filesystem-layer crypto on inline-encrypted files.
> 
> Signed-off-by: Eric Biggers <ebiggers@google.com>
> Signed-off-by: Satya Tangirala <satyat@google.com>

You've changed enough in this patch that you should probably should add your
Co-developed-by, or at least summarize your changes in between the Signed-off-by
(e.g. "[satyat: use SB_INLINECRYPT and update docs]")

> ---
>  Documentation/admin-guide/ext4.rst |  4 ++++
>  fs/buffer.c                        |  7 ++++---
>  fs/ext4/ext4.h                     |  1 +
>  fs/ext4/inode.c                    |  4 ++--
>  fs/ext4/page-io.c                  |  6 ++++--
>  fs/ext4/readpage.c                 | 11 ++++++++---
>  fs/ext4/super.c                    | 19 +++++++++++++++++++
>  7 files changed, 42 insertions(+), 10 deletions(-)
> 
> diff --git a/Documentation/admin-guide/ext4.rst b/Documentation/admin-guide/ext4.rst
> index 9443fcef1876..b7cd3bdf827e 100644
> --- a/Documentation/admin-guide/ext4.rst
> +++ b/Documentation/admin-guide/ext4.rst
> @@ -395,6 +395,10 @@ When mounting an ext4 filesystem, the following option are accepted:
>          Documentation/filesystems/dax.txt.  Note that this option is
>          incompatible with data=journal.
>  
> +  inlinecrypt
> +        Use blk-crypto, rather than fscrypt, for file content en/decryption.
> +        See Documentation/block/inline-encryption.rst.

"fscrypt" refers to the ext4 encryption feature itself.  I.e., when inline
encryption is enabled, fscrypt is still being used.  Instead you probably want
to write something like:

	Encrypt/decrypt the contents of encrypted files using the blk-crypto
	framework rather than filesystem-layer encryption.  This allows the use
	of inline encryption hardware.  The on-disk format is unaffected.  For
	more details, see Documentation/block/inline-encryption.rst.

> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index 4441331d06cc..3917f4b3ec30 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -1151,6 +1151,7 @@ struct ext4_inode_info {
>  #define EXT4_MOUNT_JOURNAL_CHECKSUM	0x800000 /* Journal checksums */
>  #define EXT4_MOUNT_JOURNAL_ASYNC_COMMIT	0x1000000 /* Journal Async Commit */
>  #define EXT4_MOUNT_WARN_ON_ERROR	0x2000000 /* Trigger WARN_ON on error */
> +#define EXT4_MOUNT_INLINECRYPT		0x4000000 /* Inline encryption support */
>  #define EXT4_MOUNT_DELALLOC		0x8000000 /* Delalloc support */
>  #define EXT4_MOUNT_DATA_ERR_ABORT	0x10000000 /* Abort on file data write */
>  #define EXT4_MOUNT_BLOCK_VALIDITY	0x20000000 /* Block validity checking */

Isn't this ext4-specific flag unused now that you switched to SB_INLINECRYPT
instead?

> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index e60aca791d3f..9ac1dd131586 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -1089,7 +1089,7 @@ static int ext4_block_write_begin(struct page *page, loff_t pos, unsigned len,
>  	}
>  	if (unlikely(err)) {
>  		page_zero_new_buffers(page, from, to);
> -	} else if (IS_ENCRYPTED(inode) && S_ISREG(inode->i_mode)) {
> +	} else if (fscrypt_inode_uses_fs_layer_crypto(inode)) {
>  		for (i = 0; i < nr_wait; i++) {
>  			int err2;
>  
> @@ -3720,7 +3720,7 @@ static int __ext4_block_zero_page_range(handle_t *handle,
>  		/* Uhhuh. Read error. Complain and punt. */
>  		if (!buffer_uptodate(bh))
>  			goto unlock;
> -		if (S_ISREG(inode->i_mode) && IS_ENCRYPTED(inode)) {
> +		if (fscrypt_inode_uses_fs_layer_crypto(inode)) {
>  			/* We expect the key to be set. */
>  			BUG_ON(!fscrypt_has_encryption_key(inode));
>  			err = fscrypt_decrypt_pagecache_blocks(page, blocksize,
> diff --git a/fs/ext4/page-io.c b/fs/ext4/page-io.c
> index 68b39e75446a..0757145a31b2 100644
> --- a/fs/ext4/page-io.c
> +++ b/fs/ext4/page-io.c
> @@ -404,6 +404,7 @@ static void io_submit_init_bio(struct ext4_io_submit *io,
>  	 * __GFP_DIRECT_RECLAIM is set, see comments for bio_alloc_bioset().
>  	 */
>  	bio = bio_alloc(GFP_NOIO, BIO_MAX_PAGES);
> +	fscrypt_set_bio_crypt_ctx_bh(bio, bh, GFP_NOIO);
>  	bio->bi_iter.bi_sector = bh->b_blocknr * (bh->b_size >> 9);
>  	bio_set_dev(bio, bh->b_bdev);
>  	bio->bi_end_io = ext4_end_bio;
> @@ -420,7 +421,8 @@ static void io_submit_add_bh(struct ext4_io_submit *io,
>  {
>  	int ret;
>  
> -	if (io->io_bio && bh->b_blocknr != io->io_next_block) {
> +	if (io->io_bio && (bh->b_blocknr != io->io_next_block ||
> +			   !fscrypt_mergeable_bio_bh(io->io_bio, bh))) {
>  submit_and_retry:
>  		ext4_io_submit(io);
>  	}
> @@ -508,7 +510,7 @@ int ext4_bio_write_page(struct ext4_io_submit *io,
>  	 * (e.g. holes) to be unnecessarily encrypted, but this is rare and
>  	 * can't happen in the common case of blocksize == PAGE_SIZE.
>  	 */
> -	if (IS_ENCRYPTED(inode) && S_ISREG(inode->i_mode) && nr_to_submit) {
> +	if (fscrypt_inode_uses_fs_layer_crypto(inode) && nr_to_submit) {
>  		gfp_t gfp_flags = GFP_NOFS;
>  		unsigned int enc_bytes = round_up(len, i_blocksize(inode));
>  
> diff --git a/fs/ext4/readpage.c b/fs/ext4/readpage.c
> index c1769afbf799..68eac0aeffad 100644
> --- a/fs/ext4/readpage.c
> +++ b/fs/ext4/readpage.c
> @@ -195,7 +195,7 @@ static void ext4_set_bio_post_read_ctx(struct bio *bio,
>  {
>  	unsigned int post_read_steps = 0;
>  
> -	if (IS_ENCRYPTED(inode) && S_ISREG(inode->i_mode))
> +	if (fscrypt_inode_uses_fs_layer_crypto(inode))
>  		post_read_steps |= 1 << STEP_DECRYPT;
>  
>  	if (ext4_need_verity(inode, first_idx))
> @@ -232,6 +232,7 @@ int ext4_mpage_readpages(struct address_space *mapping,
>  	const unsigned blkbits = inode->i_blkbits;
>  	const unsigned blocks_per_page = PAGE_SIZE >> blkbits;
>  	const unsigned blocksize = 1 << blkbits;
> +	sector_t next_block;
>  	sector_t block_in_file;
>  	sector_t last_block;
>  	sector_t last_block_in_file;
> @@ -264,7 +265,8 @@ int ext4_mpage_readpages(struct address_space *mapping,
>  		if (page_has_buffers(page))
>  			goto confused;
>  
> -		block_in_file = (sector_t)page->index << (PAGE_SHIFT - blkbits);
> +		block_in_file = next_block =
> +			(sector_t)page->index << (PAGE_SHIFT - blkbits);
>  		last_block = block_in_file + nr_pages * blocks_per_page;
>  		last_block_in_file = (ext4_readpage_limit(inode) +
>  				      blocksize - 1) >> blkbits;
> @@ -364,7 +366,8 @@ int ext4_mpage_readpages(struct address_space *mapping,
>  		 * This page will go to BIO.  Do we need to send this
>  		 * BIO off first?
>  		 */
> -		if (bio && (last_block_in_bio != blocks[0] - 1)) {
> +		if (bio && (last_block_in_bio != blocks[0] - 1 ||
> +			    !fscrypt_mergeable_bio(bio, inode, next_block))) {
>  		submit_and_realloc:
>  			submit_bio(bio);
>  			bio = NULL;
> @@ -376,6 +379,8 @@ int ext4_mpage_readpages(struct address_space *mapping,
>  			 */
>  			bio = bio_alloc(GFP_KERNEL,
>  				min_t(int, nr_pages, BIO_MAX_PAGES));
> +			fscrypt_set_bio_crypt_ctx(bio, inode, next_block,
> +						  GFP_KERNEL);
>  			ext4_set_bio_post_read_ctx(bio, inode, page->index);
>  			bio_set_dev(bio, bdev);
>  			bio->bi_iter.bi_sector = blocks[0] << (blkbits - 9);
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index f464dff09774..490e748b048c 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -1504,6 +1504,7 @@ enum {
>  	Opt_journal_path, Opt_journal_checksum, Opt_journal_async_commit,
>  	Opt_abort, Opt_data_journal, Opt_data_ordered, Opt_data_writeback,
>  	Opt_data_err_abort, Opt_data_err_ignore, Opt_test_dummy_encryption,
> +	Opt_inlinecrypt,
>  	Opt_usrjquota, Opt_grpjquota, Opt_offusrjquota, Opt_offgrpjquota,
>  	Opt_jqfmt_vfsold, Opt_jqfmt_vfsv0, Opt_jqfmt_vfsv1, Opt_quota,
>  	Opt_noquota, Opt_barrier, Opt_nobarrier, Opt_err,
> @@ -1601,6 +1602,7 @@ static const match_table_t tokens = {
>  	{Opt_noinit_itable, "noinit_itable"},
>  	{Opt_max_dir_size_kb, "max_dir_size_kb=%u"},
>  	{Opt_test_dummy_encryption, "test_dummy_encryption"},
> +	{Opt_inlinecrypt, "inlinecrypt"},
>  	{Opt_nombcache, "nombcache"},
>  	{Opt_nombcache, "no_mbcache"},	/* for backward compatibility */
>  	{Opt_removed, "check=none"},	/* mount option from ext2/3 */
> @@ -1812,6 +1814,11 @@ static const struct mount_opts {
>  	{Opt_jqfmt_vfsv1, QFMT_VFS_V1, MOPT_QFMT},
>  	{Opt_max_dir_size_kb, 0, MOPT_GTE0},
>  	{Opt_test_dummy_encryption, 0, MOPT_GTE0},
> +#ifdef CONFIG_FS_ENCRYPTION_INLINE_CRYPT
> +	{Opt_inlinecrypt, EXT4_MOUNT_INLINECRYPT, MOPT_SET},
> +#else
> +	{Opt_inlinecrypt, EXT4_MOUNT_INLINECRYPT, MOPT_NOSUPPORT},
> +#endif
>  	{Opt_nombcache, EXT4_MOUNT_NO_MBCACHE, MOPT_SET},
>  	{Opt_err, 0, 0}
>  };
> @@ -1888,6 +1895,13 @@ static int handle_mount_opt(struct super_block *sb, char *opt, int token,
>  	case Opt_nolazytime:
>  		sb->s_flags &= ~SB_LAZYTIME;
>  		return 1;
> +	case Opt_inlinecrypt:
> +#ifdef CONFIG_FS_ENCRYPTION_INLINE_CRYPT
> +		sb->s_flags |= SB_INLINE_CRYPT;
> +#else
> +		ext4_msg(sb, KERN_ERR, "inline encryption not supported");
> +#endif
> +		return 1;
>  	}
>  
>  	for (m = ext4_mount_opts; m->token != Opt_err; m++)
> @@ -2300,6 +2314,8 @@ static int _ext4_show_options(struct seq_file *seq, struct super_block *sb,
>  		SEQ_OPTS_PUTS("data_err=abort");
>  	if (DUMMY_ENCRYPTION_ENABLED(sbi))
>  		SEQ_OPTS_PUTS("test_dummy_encryption");
> +	if (sb->s_flags & SB_INLINE_CRYPT)
> +		SEQ_OPTS_PUTS("inlinecrypt");

If we're going with the VFS-level mount option flag, it looks like the code to
show it should go in show_sb_opts() in fs/proc_namespace.c instead of here.

> @@ -3808,6 +3824,9 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
>  	 */
>  	sbi->s_li_wait_mult = EXT4_DEF_LI_WAIT_MULT;
>  
> +	/* disable blk-crypto file content encryption by default */
> +	sb->s_flags &= ~SB_INLINE_CRYPT;
> +

Don't the flags default to 0?  If they do, this part is unnecessary.

- Eric