From: Eric Biggers <ebiggers@kernel.org>
To: Chandan Rajendra <chandan@linux.ibm.com>
Cc: tytso@mit.edu, linux-f2fs-devel@lists.sourceforge.net,
hch@infradead.org, linux-fscrypt@vger.kernel.org,
adilger.kernel@dilger.ca, linux-fsdevel@vger.kernel.org,
jaegeuk@kernel.org, linux-ext4@vger.kernel.org
Subject: Re: [f2fs-dev] [PATCH V2 10/13] fscrypt_encrypt_page: Loop across all blocks mapped by a page range
Date: Tue, 30 Apr 2019 16:08:41 -0700 [thread overview]
Message-ID: <20190430230840.GE48973@gmail.com> (raw)
In-Reply-To: <20190430171133.GC48973@gmail.com>
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@linux.ibm.com>
> > ---
> > 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?
Thanks!
- Eric
next prev parent reply other threads:[~2019-04-30 23:08 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-28 4:31 [PATCH V2 00/13] Consolidate FS read I/O callbacks code Chandan Rajendra
2019-04-28 4:31 ` [PATCH V2 01/13] ext4: Clear BH_Uptodate flag on decryption error Chandan Rajendra
2019-04-28 4:31 ` [PATCH V2 02/13] Consolidate "read callbacks" into a new file Chandan Rajendra
2019-04-30 0:00 ` Eric Biggers
2019-05-01 12:30 ` Chandan Rajendra
2019-04-30 1:37 ` Chao Yu
2019-05-01 12:31 ` Chandan Rajendra
2019-04-30 18:05 ` Eric Biggers
2019-05-01 12:32 ` Chandan Rajendra
2019-04-28 4:31 ` [PATCH V2 03/13] fsverity: Add call back to decide if verity check has to be performed Chandan Rajendra
2019-04-30 21:10 ` Jeremy Sowden
2019-05-01 12:33 ` Chandan Rajendra
2019-04-28 4:31 ` [PATCH V2 04/13] fsverity: Add call back to determine readpage limit Chandan Rajendra
2019-04-28 4:31 ` [PATCH V2 05/13] fs/mpage.c: Integrate read callbacks Chandan Rajendra
2019-04-28 4:31 ` [PATCH V2 06/13] ext4: Wire up ext4_readpage[s] to use mpage_readpage[s] Chandan Rajendra
2019-04-28 4:31 ` [PATCH V2 07/13] Add decryption support for sub-pagesized blocks Chandan Rajendra
2019-04-30 0:38 ` Eric Biggers
2019-05-01 13:40 ` Chandan Rajendra
2019-04-28 4:31 ` [PATCH V2 08/13] ext4: Decrypt all boundary blocks when doing buffered write Chandan Rajendra
2019-04-28 4:31 ` [PATCH V2 09/13] ext4: Decrypt the block that needs to be partially zeroed Chandan Rajendra
2019-04-28 4:31 ` [PATCH V2 10/13] fscrypt_encrypt_page: Loop across all blocks mapped by a page range Chandan Rajendra
2019-04-30 17:11 ` Eric Biggers
2019-04-30 23:08 ` Eric Biggers [this message]
2019-05-01 14:49 ` [f2fs-dev] " Chandan Rajendra
2019-05-01 22:29 ` Eric Biggers
2019-05-02 5:52 ` Chandan Rajendra
2019-05-02 18:16 ` Eric Biggers
2019-04-28 4:31 ` [PATCH V2 11/13] ext4: Compute logical block and the page range to be encrypted Chandan Rajendra
2019-04-30 17:01 ` Eric Biggers
2019-05-01 14:11 ` Chandan Rajendra
2019-04-28 4:31 ` [PATCH V2 12/13] fscrypt_zeroout_range: Encrypt all zeroed out blocks of a page Chandan Rajendra
2019-04-30 16:51 ` Eric Biggers
2019-05-01 14:22 ` Chandan Rajendra
2019-04-28 4:31 ` [PATCH V2 13/13] ext4: Enable encryption for subpage-sized blocks Chandan Rajendra
2019-04-30 0:27 ` [PATCH V2 00/13] Consolidate FS read I/O callbacks code Matthew Wilcox
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