Re: [PATCH v3 15/22] btrfs: encrypt normal file extent data if appropriate

Josef Bacik
2022-10-21T20:58:37Z

On Thu, Oct 20, 2022 at 12:58:34PM -0400, Sweet Tea Dorminy wrote:
> From: Omar Sandoval <osandov@osandov.com>
>
> Add in the necessary calls to encrypt and decrypt data to achieve
> encryption of normal data.
>
> Since these are all page cache pages being encrypted, we can't encrypt
> them in place and must encrypt/decrypt into a new page. fscrypt provides a pool
> of pages for this purpose, which it calls bounce pages. For IO of
> encrypted data, we use a bounce page for the actual IO, and
> encrypt/decrypt from/to the actual page cache page on either side of the
> IO.
>
> Signed-off-by: Omar Sandoval <osandov@osandov.com>
> Signed-off-by: Sweet Tea Dorminy <sweettea-kernel@dorminy.me>
> ---
> fs/btrfs/extent_io.c | 56 ++++++++++++++++++++++++++++++++++++-----
> fs/btrfs/file-item.c | 9 +++++--
> fs/btrfs/fscrypt.c | 32 ++++++++++++++++++++++-
> fs/btrfs/tree-checker.c | 11 +++++---
> 4 files changed, 96 insertions(+), 12 deletions(-)
>
> diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
> index 4e4f28387ace..94d0636aafd0 100644
> --- a/fs/btrfs/extent_io.c
> +++ b/fs/btrfs/extent_io.c
> @@ -113,6 +113,7 @@ static void submit_one_bio(struct btrfs_bio_ctrl *bio_ctrl)
> {
> struct bio *bio;
> struct bio_vec *bv;
> + struct page *first_page;
> struct inode *inode;
> int mirror_num;
>
> @@ -121,13 +122,17 @@ static void submit_one_bio(struct btrfs_bio_ctrl *bio_ctrl)
>
> bio = bio_ctrl->bio;
> bv = bio_first_bvec_all(bio);
> - inode = bv->bv_page->mapping->host;
> + first_page = bio_first_page_all(bio);
> + if (fscrypt_is_bounce_page(first_page))
> + inode = fscrypt_pagecache_page(first_page)->mapping->host;
> + else
> + inode = first_page->mapping->host;
> mirror_num = bio_ctrl->mirror_num;
>
> /* Caller should ensure the bio has at least some range added */
> ASSERT(bio->bi_iter.bi_size);
>
> - btrfs_bio(bio)->file_offset = page_offset(bv->bv_page) + bv->bv_offset;
> + btrfs_bio(bio)->file_offset = page_offset(first_page) + bv->bv_offset;
>
> if (!is_data_inode(inode))
> btrfs_submit_metadata_bio(inode, bio, mirror_num);
> @@ -1014,9 +1019,19 @@ static void end_bio_extent_writepage(struct btrfs_bio *bbio)
> ASSERT(!bio_flagged(bio, BIO_CLONED));
> bio_for_each_segment_all(bvec, bio, iter_all) {
> struct page *page = bvec->bv_page;
> - struct inode *inode = page->mapping->host;
> - struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
> - const u32 sectorsize = fs_info->sectorsize;
> + struct inode *inode;
> + struct btrfs_fs_info *fs_info;
> + u32 sectorsize;
> + struct page *bounce_page = NULL;
> +
> + if (fscrypt_is_bounce_page(page)) {
> + bounce_page = page;
> + page = fscrypt_pagecache_page(bounce_page);
> + }
> +
> + inode = page->mapping->host;
> + fs_info = btrfs_sb(inode->i_sb);
> + sectorsize = fs_info->sectorsize;
>
> /* Our read/write should always be sector aligned. */
> if (!IS_ALIGNED(bvec->bv_offset, sectorsize))
> @@ -1037,7 +1052,7 @@ static void end_bio_extent_writepage(struct btrfs_bio *bbio)
> }
>
> end_extent_writepage(page, error, start, end);
> -
> + fscrypt_free_bounce_page(bounce_page);
> btrfs_page_clear_writeback(fs_info, page, start, bvec->bv_len);
> }
>
> @@ -1229,6 +1244,17 @@ static void end_bio_extent_readpage(struct btrfs_bio *bbio)
> }
> }
>
> + if (likely(uptodate)) {
> + if (fscrypt_inode_uses_fs_layer_crypto(inode)) {
> + int ret = fscrypt_decrypt_pagecache_blocks(page,
> + bvec->bv_len,
> + bvec->bv_offset);
> + if (ret) {
> + error_bitmap = (unsigned int) -1;
> + uptodate = false;
> + }

Messed up indenting.

> + }
> + }
> if (likely(uptodate)) {
> loff_t i_size = i_size_read(inode);
> pgoff_t end_index = i_size >> PAGE_SHIFT;
> @@ -1563,11 +1589,29 @@ static int submit_extent_page(blk_opf_t opf,
> bool force_bio_submit)
> {
> int ret = 0;
> + struct page *bounce_page = NULL;
> struct btrfs_inode *inode = BTRFS_I(page->mapping->host);
> unsigned int cur = pg_offset;
>
> ASSERT(bio_ctrl);
>
> + if ((opf & REQ_OP_MASK) == REQ_OP_WRITE &&
> + fscrypt_inode_uses_fs_layer_crypto(&inode->vfs_inode)) {
> + gfp_t gfp_flags = GFP_NOFS;
> +
> + if (bio_ctrl->bio)
> + gfp_flags = GFP_NOWAIT | __GFP_NOWARN;
> + else
> + gfp_flags = GFP_NOFS;
> + bounce_page = fscrypt_encrypt_pagecache_blocks(page, size,
> + pg_offset,
> + gfp_flags);
> + if (IS_ERR(bounce_page))
> + return PTR_ERR(bounce_page);
> + page = bounce_page;
> + pg_offset = 0;
> + }
> +
> ASSERT(pg_offset < PAGE_SIZE && size <= PAGE_SIZE &&
> pg_offset + size <= PAGE_SIZE);
>
> diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c
> index 598dff14078f..e4ec6a97a85c 100644
> --- a/fs/btrfs/file-item.c
> +++ b/fs/btrfs/file-item.c
> @@ -676,8 +676,13 @@ blk_status_t btrfs_csum_one_bio(struct btrfs_inode *inode, struct bio *bio,
> shash->tfm = fs_info->csum_shash;
>
> bio_for_each_segment(bvec, bio, iter) {
> - if (use_page_offsets)
> - offset = page_offset(bvec.bv_page) + bvec.bv_offset;
> + if (use_page_offsets) {
> + struct page *page = bvec.bv_page;
> +
> + if (fscrypt_is_bounce_page(page))
> + page = fscrypt_pagecache_page(page);
> + offset = page_offset(page) + bvec.bv_offset;
> + }
>
> if (!ordered) {
> ordered = btrfs_lookup_ordered_extent(inode, offset);
> diff --git a/fs/btrfs/fscrypt.c b/fs/btrfs/fscrypt.c
> index 717a9c244306..324436cba989 100644
> --- a/fs/btrfs/fscrypt.c
> +++ b/fs/btrfs/fscrypt.c
> @@ -175,7 +175,37 @@ static int btrfs_fscrypt_get_extent_context(const struct inode *inode,
> size_t *extent_offset,
> size_t *extent_length)
> {
> - return len;
> + u64 offset = lblk_num << inode->i_blkbits;
> + struct extent_map *em;
> +
> + /* Since IO must be in progress on this extent, this must succeed */
> + em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, offset, PAGE_SIZE);

If the bulk of the code is in the normal case, you need to invert the condition.
So instead

if (!em)
return -EINVAL

// the rest of hte code at a normal indentation.

Thanks,

Josef