linux-ext4 - Bio: Determining encrypted vs plain content

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Date:   Wed, 13 Sep 2017 15:33:33 +0530
From:   Chandan Rajendra <chandan@...ux.vnet.ibm.com>
To:     linux-ext4@...r.kernel.org
Cc:     "Theodore Ts'o" <tytso@....edu>,
        Michael Halcrow <mhalcrow@...gle.com>,
        linux-fsdevel@...r.kernel.org
Subject: Bio: Determining encrypted vs plain content

Hi,

I am trying to get encryption to work on block size < page size scenario
(e.g. 4k block size on ppc64's 64k page size).

One of the last scenarios that I am working on is to decrypt a page whose
blocks are not contiguously stored on the underlying disk. 

The code assumes that bio's pages are supposed to be decrypted if 
bio-b_private has a non-zero value (See the definition of 
ext4_bio_encrypted()).

Instead of that, why can't the code extract the first page from the first bio
vector of the bio and then use ext4_encrypted_inode(page->mapping->host) to
determine if bio's pages are supposed to contain encrypted data? Was there a
specific reason to not use ext4_encrypted_inode()?

-- 
chandan