From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Eric Biggers <ebiggers@google.com>
Date: Fri, 24 Jul 2020 18:44:58 +0000
Subject: ANDROID: ext4: support direct I/O with fscrypt using blk-crypto

Wire up ext4 with fscrypt direct I/O support. Direct I/O with fscrypt is
only supported through blk-crypto (i.e. CONFIG_BLK_INLINE_ENCRYPTION must
have been enabled, the 'inlinecrypt' mount option must have been specified,
and either hardware inline encryption support must be present or
CONFIG_BLK_INLINE_ENCYRPTION_FALLBACK must have been enabled). Further,
direct I/O on encrypted files is only supported when I/O is aligned
to the filesystem block size (which is *not* necessarily the same as the
block device's block size).

fscrypt_limit_io_blocks() is called before setting up the iomap to ensure
that the blocks of each bio that iomap will submit will have contiguous
DUNs. Note that fscrypt_limit_io_blocks() is normally a no-op, as normally
the DUNs simply increment along with the logical blocks. But it's needed
to handle an edge case in one of the fscrypt IV generation methods.

[CPNOTE: 25/05/21] Lee: No update since v8 was posted in January - poked the MLs
[CPNOTE: 26/05/21] Lee: Satya will work to push these forward over the next week
[CPNOTE: 22/07/21] Lee: v9 was posted 7 weeks ago with no reviews - poked again
[CPNOTE: 04/08/21] Lee: Eric and Satya are still working on this [0]

[0] https://lore.kernel.org/linux-xfs/YPmFSw4JbWnIozSZ@gmail.com/

Signed-off-by: Eric Biggers <ebiggers@google.com>
Co-developed-by: Satya Tangirala <satyat@google.com>
Signed-off-by: Satya Tangirala <satyat@google.com>
Reviewed-by: Jaegeuk Kim <jaegeuk@kernel.org>

Bug: 162255927
Link: https://lore.kernel.org/r/20200724184501.1651378-5-satyat@google.com
Change-Id: Ia3d869cefabdff070f4e77c46190351f6cb5d74c
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 fs/ext4/file.c  | 10 ++++++----
 fs/ext4/inode.c |  8 ++++++++
 2 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/fs/ext4/file.c b/fs/ext4/file.c
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -36,9 +36,11 @@
 #include "acl.h"
 #include "truncate.h"
 
-static bool ext4_dio_supported(struct inode *inode)
+static bool ext4_dio_supported(struct kiocb *iocb, struct iov_iter *iter)
 {
-	if (IS_ENABLED(CONFIG_FS_ENCRYPTION) && IS_ENCRYPTED(inode))
+	struct inode *inode = file_inode(iocb->ki_filp);
+
+	if (!fscrypt_dio_supported(iocb, iter))
 		return false;
 	if (fsverity_active(inode))
 		return false;
@@ -61,7 +63,7 @@ static ssize_t ext4_dio_read_iter(struct kiocb *iocb, struct iov_iter *to)
 		inode_lock_shared(inode);
 	}
 
-	if (!ext4_dio_supported(inode)) {
+	if (!ext4_dio_supported(iocb, to)) {
 		inode_unlock_shared(inode);
 		/*
 		 * Fallback to buffered I/O if the operation being performed on
@@ -511,7 +513,7 @@ static ssize_t ext4_dio_write_iter(struct kiocb *iocb, struct iov_iter *from)
 	}
 
 	/* Fallback to buffered I/O if the inode does not support direct I/O. */
-	if (!ext4_dio_supported(inode)) {
+	if (!ext4_dio_supported(iocb, from)) {
 		if (ilock_shared)
 			inode_unlock_shared(inode);
 		else
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3444,6 +3444,14 @@ static int ext4_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
 	if (ret < 0)
 		return ret;
 out:
+
+	/*
+	 * When inline encryption is enabled, sometimes I/O to an encrypted file
+	 * has to be broken up to guarantee DUN contiguity. Handle this by
+	 * limiting the length of the mapping returned.
+	 */
+	map.m_len = fscrypt_limit_io_blocks(inode, map.m_lblk, map.m_len);
+
 	ext4_set_iomap(inode, iomap, &map, offset, length);
 
 	return 0;