Re: [PATCH v6 7/9] fscrypt: add inline encryption support

Eric Biggers
2020-01-14T21:12:47Z

On Wed, Dec 18, 2019 at 06:51:34AM -0800, Satya Tangirala wrote:
> diff --git a/fs/crypto/bio.c b/fs/crypto/bio.c
> index 1f4b8a277060..d28d8e803554 100644
> --- a/fs/crypto/bio.c
> +++ b/fs/crypto/bio.c
> @@ -46,26 +46,35 @@ int fscrypt_zeroout_range(const struct inode *inode, pgoff_t lblk,
> {
> const unsigned int blockbits = inode->i_blkbits;
> const unsigned int blocksize = 1 << blockbits;
> + const bool inlinecrypt = fscrypt_inode_uses_inline_crypto(inode);
> struct page *ciphertext_page;
> struct bio *bio;
> int ret, err = 0;
>
> - ciphertext_page = fscrypt_alloc_bounce_page(GFP_NOWAIT);
> - if (!ciphertext_page)
> - return -ENOMEM;
> + if (inlinecrypt) {
> + ciphertext_page = ZERO_PAGE(0);
> + } else {
> + ciphertext_page = fscrypt_alloc_bounce_page(GFP_NOWAIT);
> + if (!ciphertext_page)
> + return -ENOMEM;
> + }
>
> while (len--) {
> - err = fscrypt_crypt_block(inode, FS_ENCRYPT, lblk,
> - ZERO_PAGE(0), ciphertext_page,
> - blocksize, 0, GFP_NOFS);
> - if (err)
> - goto errout;
> + if (!inlinecrypt) {
> + err = fscrypt_crypt_block(inode, FS_ENCRYPT, lblk,
> + ZERO_PAGE(0), ciphertext_page,
> + blocksize, 0, GFP_NOFS);
> + if (err)
> + goto errout;
> + }
>
> bio = bio_alloc(GFP_NOWAIT, 1);
> if (!bio) {
> err = -ENOMEM;
> goto errout;
> }
> + fscrypt_set_bio_crypt_ctx(bio, inode, lblk, GFP_NOIO);
> +
> bio_set_dev(bio, inode->i_sb->s_bdev);
> bio->bi_iter.bi_sector = pblk << (blockbits - 9);
> bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
> @@ -87,7 +96,8 @@ int fscrypt_zeroout_range(const struct inode *inode, pgoff_t lblk,
> }
> err = 0;
> errout:
> - fscrypt_free_bounce_page(ciphertext_page);
> + if (!inlinecrypt)
> + fscrypt_free_bounce_page(ciphertext_page);
> return err;
> }
> EXPORT_SYMBOL(fscrypt_zeroout_range);

FYI, I've just applied a patch
(https://lore.kernel.org/r/20191226160813.53182-1-ebiggers@kernel.org/)
to fscrypt.git#master that optimizes this function to write multiple pages at a
time. So this part of this patch will need to be reworked. I suggest just
handling the inline and fs-layer encryption cases separately.

I maintain a testing branch that has all the pending patches I'm interested in
applied, so I actually already hacked together the following to resolve the
conflict. Please double check it carefully before using it in v7 though:

static int fscrypt_zeroout_range_inlinecrypt(const struct inode *inode,
pgoff_t lblk,
sector_t pblk, unsigned int len)
{
const unsigned int blockbits = inode->i_blkbits;
const unsigned int blocks_per_page_bits = PAGE_SHIFT - blockbits;
const unsigned int blocks_per_page = 1 << blocks_per_page_bits;
unsigned int i;
struct bio *bio;
int ret, err;

/* This always succeeds since __GFP_DIRECT_RECLAIM is set. */
bio = bio_alloc(GFP_NOFS, BIO_MAX_PAGES);

do {
bio_set_dev(bio, inode->i_sb->s_bdev);
bio->bi_iter.bi_sector = pblk << (blockbits - 9);
bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
fscrypt_set_bio_crypt_ctx(bio, inode, lblk, GFP_NOFS);

i = 0;
do {
unsigned int blocks_this_page =
min(len, blocks_per_page);
unsigned int bytes_this_page =
blocks_this_page << blockbits;

ret = bio_add_page(bio, ZERO_PAGE(0),
bytes_this_page, 0);
if (WARN_ON(ret != bytes_this_page)) {
err = -EIO;
goto out;
}
lblk += blocks_this_page;
pblk += blocks_this_page;
len -= blocks_this_page;
} while (++i != BIO_MAX_PAGES && len != 0);

err = submit_bio_wait(bio);
if (err)
goto out;
bio_reset(bio);
} while (len != 0);
err = 0;
out:
bio_put(bio);
return err;
}