On Wednesday, February 21, 2018 6:24:54 AM IST Eric Biggers wrote:
> On Mon, Feb 12, 2018 at 03:13:46PM +0530, Chandan Rajendra wrote:
> > This commit splits the functionality of fscrypt_encrypt_block(). The
> > allocation of fscrypt context and cipher text page is moved to a new
> > function fscrypt_prep_ciphertext_page().
> >
> > ext4_bio_write_page() is modified to appropriately make use of the above
> > two functions.
> >
> > Signed-off-by: Chandan Rajendra <chandan@xxxxxxxxxxxxxxxxxx>
>
> Well, this patch also modifies ext4_bio_write_page() to support the blocksize <
> pagesize case. The commit message makes it sound like it's just refactoring.
>
> > diff --git a/fs/ext4/page-io.c b/fs/ext4/page-io.c
> > index 0a4a1e7..1e869d5 100644
> > --- a/fs/ext4/page-io.c
> > +++ b/fs/ext4/page-io.c
> > @@ -419,9 +419,12 @@ int ext4_bio_write_page(struct ext4_io_submit *io,
> > struct inode *inode = page->mapping->host;
> > unsigned block_start;
> > struct buffer_head *bh, *head;
> > + u64 blk_nr;
> > + gfp_t gfp_flags = GFP_NOFS;
> > int ret = 0;
> > int nr_submitted = 0;
> > int nr_to_submit = 0;
> > + int blocksize = (1 << inode->i_blkbits);
> >
> > BUG_ON(!PageLocked(page));
> > BUG_ON(PageWriteback(page));
> > @@ -475,15 +478,11 @@ int ext4_bio_write_page(struct ext4_io_submit *io,
> > nr_to_submit++;
> > } while ((bh = bh->b_this_page) != head);
> >
> > - bh = head = page_buffers(page);
> > -
> > - if (ext4_encrypted_inode(inode) && S_ISREG(inode->i_mode) &&
> > - nr_to_submit) {
> > - gfp_t gfp_flags = GFP_NOFS;
> > -
> > - retry_encrypt:
> > - data_page = fscrypt_encrypt_block(inode, page, PAGE_SIZE, 0,
> > - page->index, gfp_flags);
> > + if (ext4_encrypted_inode(inode) && S_ISREG(inode->i_mode)
> > + && nr_to_submit) {
> > + retry_prep_ciphertext_page:
> > + data_page = fscrypt_prep_ciphertext_page(inode, page,
> > + gfp_flags);
> > if (IS_ERR(data_page)) {
> > ret = PTR_ERR(data_page);
> > if (ret == -ENOMEM && wbc->sync_mode == WB_SYNC_ALL) {
> > @@ -492,17 +491,28 @@ int ext4_bio_write_page(struct ext4_io_submit *io,
> > congestion_wait(BLK_RW_ASYNC, HZ/50);
> > }
> > gfp_flags |= __GFP_NOFAIL;
> > - goto retry_encrypt;
> > + goto retry_prep_ciphertext_page;
> > }
> > data_page = NULL;
> > goto out;
> > }
> > }
> >
> > + blk_nr = page->index << (PAGE_SHIFT - inode->i_blkbits);
> > +
> > /* Now submit buffers to write */
> > + bh = head = page_buffers(page);
> > do {
> > if (!buffer_async_write(bh))
> > continue;
> > +
> > + if (ext4_encrypted_inode(inode) && S_ISREG(inode->i_mode)) {
> > + ret = fscrypt_encrypt_block(inode, page, data_page, blocksize,
> > + bh_offset(bh), blk_nr, gfp_flags);
> > + if (ret)
> > + break;
> > + }
> > +
> > ret = io_submit_add_bh(io, inode,
> > data_page ? data_page : page, bh);
> > if (ret) {
> > @@ -515,12 +525,12 @@ int ext4_bio_write_page(struct ext4_io_submit *io,
> > }
> > nr_submitted++;
> > clear_buffer_dirty(bh);
> > - } while ((bh = bh->b_this_page) != head);
> > + } while (++blk_nr, (bh = bh->b_this_page) != head);
> >
> > /* Error stopped previous loop? Clean up buffers... */
> > if (ret) {
> > out:
> > - if (data_page)
> > + if (data_page && bh == head)
> > fscrypt_restore_control_page(data_page);
> > printk_ratelimited(KERN_ERR "%s: ret = %d\n", __func__, ret);
> > redirty_page_for_writepage(wbc, page);
>
> I'm wondering why you didn't move the crypto stuff in ext4_bio_write_page() into
> a separate function like I had suggested? It's true we don't have to encrypt
> all the blocks in the page at once, but it would make the crypto stuff more
> self-contained.
Eric, Are you suggesting that the entire block of code that has invocations to
fscrypt_prep_ciphertext_page() and fscrypt_encrypt_block() be moved to a
separate function that gets defined in fscrypt module?
If yes, In Ext4, We have the invocation of io_submit_add_bh() being
interleaved with calls to fscrypt_encrypt_block().
--
chandan
