linux-ext4 - [PATCH v2 10/14] fscrypt: decrypt only the needed blocks in __fscrypt_decrypt

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Message-Id: <20190520162952.156212-11-ebiggers@kernel.org>
Date:   Mon, 20 May 2019 09:29:48 -0700
From:   Eric Biggers <ebiggers@...nel.org>
To:     linux-fscrypt@...r.kernel.org
Cc:     linux-ext4@...r.kernel.org, linux-f2fs-devel@...ts.sourceforge.net,
        linux-mtd@...ts.infradead.org,
        Chandan Rajendra <chandan@...ux.ibm.com>
Subject: [PATCH v2 10/14] fscrypt: decrypt only the needed blocks in __fscrypt_decrypt_bio()

From: Eric Biggers <ebiggers@...gle.com>

In __fscrypt_decrypt_bio(), only decrypt the blocks that actually
comprise the bio, rather than assuming blocksize == PAGE_SIZE and
decrypting the entirety of every page used in the bio.

This is in preparation for allowing encryption on ext4 filesystems with
blocksize != PAGE_SIZE.

This is based on work by Chandan Rajendra.

Reviewed-by: Chandan Rajendra <chandan@...ux.ibm.com>
Signed-off-by: Eric Biggers <ebiggers@...gle.com>
---
 fs/crypto/bio.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/crypto/bio.c b/fs/crypto/bio.c
index 61da06fda45cc..82da2510721f6 100644
--- a/fs/crypto/bio.c
+++ b/fs/crypto/bio.c
@@ -33,8 +33,8 @@ static void __fscrypt_decrypt_bio(struct bio *bio, bool done)
 
 	bio_for_each_segment_all(bv, bio, iter_all) {
 		struct page *page = bv->bv_page;
-		int ret = fscrypt_decrypt_pagecache_blocks(page, PAGE_SIZE, 0);
-
+		int ret = fscrypt_decrypt_pagecache_blocks(page, bv->bv_len,
+							   bv->bv_offset);
 		if (ret)
 			SetPageError(page);
 		else if (done)
-- 
2.21.0.1020.gf2820cf01a-goog