[PATCH v9 7/9] ext4: support direct I/O with fscrypt using blk-crypto

Satya Tangirala
2021-06-04T21:10:26Z

From: Eric Biggers <ebiggers@google.com>

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 the *length* of the
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.

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>
Acked-by: Theodore Ts'o <tytso@mit.edu>
---
fs/ext4/file.c | 10 ++++++----
fs/ext4/inode.c | 7 +++++++
2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 816dedcbd541..a2898a496c4e 100644
--- 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
index fe6045a46599..fe8006efb5ef 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3481,6 +3481,13 @@ 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;
--
2.32.0.rc1.229.g3e70b5a671-goog