Hi Chandan, On Wed, May 01, 2019 at 08:19:35PM +0530, Chandan Rajendra wrote: > On Wednesday, May 1, 2019 4:38:41 AM IST Eric Biggers wrote: > > On Tue, Apr 30, 2019 at 10:11:35AM -0700, Eric Biggers wrote: > > > On Sun, Apr 28, 2019 at 10:01:18AM +0530, Chandan Rajendra wrote: > > > > For subpage-sized blocks, this commit now encrypts all blocks mapped by > > > > a page range. > > > > > > > > Signed-off-by: Chandan Rajendra <chandan@xxxxxxxxxxxxx> > > > > --- > > > > fs/crypto/crypto.c | 37 +++++++++++++++++++++++++------------ > > > > 1 file changed, 25 insertions(+), 12 deletions(-) > > > > > > > > diff --git a/fs/crypto/crypto.c b/fs/crypto/crypto.c > > > > index 4f0d832cae71..2d65b431563f 100644 > > > > --- a/fs/crypto/crypto.c > > > > +++ b/fs/crypto/crypto.c > > > > @@ -242,18 +242,26 @@ struct page *fscrypt_encrypt_page(const struct inode *inode, > > > > > > Need to update the function comment to clearly explain what this function > > > actually does now. > > > > > > > { > > > > struct fscrypt_ctx *ctx; > > > > struct page *ciphertext_page = page; > > > > + int i, page_nr_blks; > > > > int err; > > > > > > > > BUG_ON(len % FS_CRYPTO_BLOCK_SIZE != 0); > > > > > > > > > > Make a 'blocksize' variable so you don't have to keep calling i_blocksize(). > > > > > > Also, you need to check whether 'len' and 'offs' are filesystem-block-aligned, > > > since the code now assumes it. > > > > > > const unsigned int blocksize = i_blocksize(inode); > > > > > > if (!IS_ALIGNED(len | offs, blocksize)) > > > return -EINVAL; > > > > > > However, did you check whether that's always true for ubifs? It looks like it > > > may expect to encrypt a prefix of a block, that is only padded to the next > > > 16-byte boundary. > > > > > > > + page_nr_blks = len >> inode->i_blkbits; > > > > + > > > > if (inode->i_sb->s_cop->flags & FS_CFLG_OWN_PAGES) { > > > > /* with inplace-encryption we just encrypt the page */ > > > > - err = fscrypt_do_page_crypto(inode, FS_ENCRYPT, lblk_num, page, > > > > - ciphertext_page, len, offs, > > > > - gfp_flags); > > > > - if (err) > > > > - return ERR_PTR(err); > > > > - > > > > + for (i = 0; i < page_nr_blks; i++) { > > > > + err = fscrypt_do_page_crypto(inode, FS_ENCRYPT, > > > > + lblk_num, page, > > > > + ciphertext_page, > > > > + i_blocksize(inode), offs, > > > > + gfp_flags); > > > > + if (err) > > > > + return ERR_PTR(err); > > > > Apparently ubifs does encrypt data shorter than the filesystem block size, so > > this part is wrong. > > > > I suggest we split this into two functions, fscrypt_encrypt_block_inplace() and > > fscrypt_encrypt_blocks(), so that it's conceptually simpler what each function > > does. Currently this works completely differently depending on whether the > > filesystem set FS_CFLG_OWN_PAGES in its fscrypt_operations, which is weird. > > > > I also noticed that using fscrypt_ctx for writes seems to be unnecessary. > > AFAICS, page_private(bounce_page) could point directly to the pagecache page. > > That would simplify things a lot, especially since then fscrypt_ctx could be > > removed entirely after you convert reads to use read_callbacks_ctx. > > > > IMO, these would be worthwhile cleanups for fscrypt by themselves, without > > waiting for the read_callbacks stuff to be finalized. Finalizing the > > read_callbacks stuff will probably require reaching a consensus about how they > > should work with future filesystem features like fsverity and compression. > > > > So to move things forward, I'm considering sending out a series with the above > > cleanups for fscrypt, plus the equivalent of your patches: > > > > "fscrypt_encrypt_page: Loop across all blocks mapped by a page range" > > "fscrypt_zeroout_range: Encrypt all zeroed out blocks of a page" > > "Add decryption support for sub-pagesized blocks" (fs/crypto/ part only) > > > > Then hopefully we can get all that applied for 5.3 so that fs/crypto/ itself is > > ready for blocksize != PAGE_SIZE; and get your changes to ext4_bio_write_page(), > > __ext4_block_zero_page_range(), and ext4_block_write_begin() applied too, so > > that ext4 is partially ready for encryption with blocksize != PAGE_SIZE. > > > > Then only the read_callbacks stuff will remain, to get encryption support into > > fs/mpage.c and fs/buffer.c. Do you think that's a good plan? > > Hi Eric, > > IMHO, I will continue posting the next version of the current patchset and if > there are no serious reservations from FS maintainers the "read callbacks" > patchset can be merged. In such a scenario, the cleanups being > non-complicated, can be merged later. > > -- > chandan > Most of the patches I have in mind are actually things that are in your patchset already, or have been requested, or will be requested eventually :-). I'm concerned that people will keep going back and forth on this patchset for a lot longer, arguing about fsverity, compression, details of the fs/crypto/ stuff, etc. Moreover it's based on unmerged patches that add the fsverity feature, so it can't be merged as-is anyway. IMO, it's also difficult for people to review the read_callbacks stuff when it's mixed in with lots of other fscrypt and ext4 changes for blocksize != PAGE_SIZE. I actually have a patchset almost ready already, so I'm going to send it out and see what you think. It *should* make things a lot easier for you, since then you can base a much smaller read_callbacks patchset on top of it. Thanks! - Eric
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