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

[Chandan Rajendra <chandan@xxxxxxxxxxxxxxxxxx>]

For block size < page size, This commit adds code to encrypt all zeroed
out blocks of a page.

Signed-off-by: Chandan Rajendra <chandan@xxxxxxxxxxxxxxxxxx>
---
 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;
+
+		for (i = 0; i < page_nr_blks; i++) {
+			err = fscrypt_do_block_crypto(inode, FS_ENCRYPT, lblk,
+						ZERO_PAGE(0), ciphertext_page,
+						inode->i_sb->s_blocksize, offset,
+						GFP_NOFS);
+			if (err)
+				goto errout;
+			lblk++;
+			offset += inode->i_sb->s_blocksize;
+		}
 
 		bio = bio_alloc(GFP_NOWAIT, 1);
 		if (!bio) {
@@ -135,9 +148,8 @@ int fscrypt_zeroout_range(const struct inode *inode, pgoff_t lblk,
 		bio->bi_iter.bi_sector =
 			pblk << (inode->i_sb->s_blocksize_bits - 9);
 		bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
-		ret = bio_add_page(bio, ciphertext_page,
-					inode->i_sb->s_blocksize, 0);
-		if (ret != inode->i_sb->s_blocksize) {
+		ret = bio_add_page(bio, ciphertext_page, page_io_len, 0);
+		if (ret != page_io_len) {
 			/* should never happen! */
 			WARN_ON(1);
 			bio_put(bio);
@@ -150,8 +162,8 @@ int fscrypt_zeroout_range(const struct inode *inode, pgoff_t lblk,
 		bio_put(bio);
 		if (err)
 			goto errout;
-		lblk++;
-		pblk++;
+		pblk += page_nr_blks;
+		len -= page_nr_blks;
 	}
 	err = 0;
 errout:
-- 
2.9.5