linux-ext4 - Re: [RFC PATCH V2 07/11] fscrypt_zeroout_range: Encrypt all zeroed out blocks of a page

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Date:   Wed, 21 Feb 2018 15:27:24 +0530
From:   Chandan Rajendra <chandan@...ux.vnet.ibm.com>
To:     Eric Biggers <ebiggers3@...il.com>
Cc:     linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-fscrypt@...r.kernel.org, tytso@....edu
Subject: Re: [RFC PATCH V2 07/11] fscrypt_zeroout_range: Encrypt all zeroed out blocks of a page

On Wednesday, February 21, 2018 6:46:48 AM IST Eric Biggers wrote:
> On Mon, Feb 12, 2018 at 03:13:43PM +0530, Chandan Rajendra wrote:
> > For block size < page size, This commit adds code to encrypt all zeroed
> > out blocks of a page.
> > 
> > Signed-off-by: Chandan Rajendra <chandan@...ux.vnet.ibm.com>
> > ---
> >  fs/crypto/bio.c | 38 +++++++++++++++++++++++++-------------
> >  1 file changed, 25 insertions(+), 13 deletions(-)
> > 
> > diff --git a/fs/crypto/bio.c b/fs/crypto/bio.c
> > index 378df08..4d0d14f 100644
> > --- a/fs/crypto/bio.c
> > +++ b/fs/crypto/bio.c
> > @@ -104,10 +104,12 @@ int fscrypt_zeroout_range(const struct inode *inode, pgoff_t lblk,
> >  {
> >  	struct fscrypt_ctx *ctx;
> >  	struct page *ciphertext_page = NULL;
> > +	unsigned int page_nr_blks;
> > +	unsigned int offset;
> > +	unsigned int page_io_len;
> >  	struct bio *bio;
> >  	int ret, err = 0;
> > -
> > -	BUG_ON(inode->i_sb->s_blocksize != PAGE_SIZE);
> > +	int i;
> >  
> >  	ctx = fscrypt_get_ctx(inode, GFP_NOFS);
> >  	if (IS_ERR(ctx))
> > @@ -119,12 +121,23 @@ int fscrypt_zeroout_range(const struct inode *inode, pgoff_t lblk,
> >  		goto errout;
> >  	}
> >  
> > -	while (len--) {
> > -		err = fscrypt_do_block_crypto(inode, FS_ENCRYPT, lblk,
> > -					     ZERO_PAGE(0), ciphertext_page,
> > -					     PAGE_SIZE, 0, GFP_NOFS);
> > -		if (err)
> > -			goto errout;
> > +	page_nr_blks = 1 << (PAGE_SHIFT - inode->i_blkbits);
> > +
> > +	while (len) {
> > +		page_nr_blks = min_t(unsigned int, page_nr_blks, len);
> > +		page_io_len = page_nr_blks << inode->i_blkbits;
> > +		offset = 0;
> 
> The 'page_io_len' variable isn't needed, since 'offset == page_io_len' after the
> encryption loop.  You can do 'bio_add_page(bio, ciphertext_page, offset, 0);'.
> 

You are right. I will fix that up in the next iteration of the patchset.


-- 
chandan