From: Eric Biggers <ebigg...@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 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 <ebigg...@google.com>
Co-developed-by: Satya Tangirala <sat...@google.com>
Signed-off-by: Satya Tangirala <sat...@google.com>
Reviewed-by: Jaegeuk Kim <jaeg...@kernel.org>
---
 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 2a01e31a032c..d534f72675d9 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
@@ -490,7 +492,7 @@ 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 44bad4bb8831..6725116ea348 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3445,6 +3445,13 @@ static int ext4_iomap_begin(struct inode *inode, loff_t 
offset, loff_t length,
        if (ret < 0)
                return ret;
 
+       /*
+        * 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;
-- 
2.28.0.rc0.142.g3c755180ce-goog



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