From: Satya Tangirala <satyat@google.com>
To: "Theodore Y . Ts'o" <tytso@mit.edu>,
Jaegeuk Kim <jaegeuk@kernel.org>,
Eric Biggers <ebiggers@kernel.org>, Chao Yu <chao@kernel.org>,
Jens Axboe <axboe@kernel.dk>,
"Darrick J . Wong" <darrick.wong@oracle.com>
Cc: linux-kernel@vger.kernel.org, linux-fscrypt@vger.kernel.org,
linux-f2fs-devel@lists.sourceforge.net,
linux-xfs@vger.kernel.org, linux-block@vger.kernel.org,
linux-ext4@vger.kernel.org, Satya Tangirala <satyat@google.com>,
Eric Biggers <ebiggers@google.com>
Subject: [PATCH v7 8/8] fscrypt: update documentation for direct I/O support
Date: Tue, 17 Nov 2020 14:07:08 +0000 [thread overview]
Message-ID: <20201117140708.1068688-9-satyat@google.com> (raw)
In-Reply-To: <20201117140708.1068688-1-satyat@google.com>
Update fscrypt documentation to reflect the addition of direct I/O support
and document the necessary conditions for direct I/O on encrypted files.
Signed-off-by: Satya Tangirala <satyat@google.com>
Reviewed-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Jaegeuk Kim <jaegeuk@kernel.org>
---
Documentation/filesystems/fscrypt.rst | 21 +++++++++++++++++++--
1 file changed, 19 insertions(+), 2 deletions(-)
diff --git a/Documentation/filesystems/fscrypt.rst b/Documentation/filesystems/fscrypt.rst
index 44b67ebd6e40..757b8aa2af9b 100644
--- a/Documentation/filesystems/fscrypt.rst
+++ b/Documentation/filesystems/fscrypt.rst
@@ -1047,8 +1047,10 @@ astute users may notice some differences in behavior:
may be used to overwrite the source files but isn't guaranteed to be
effective on all filesystems and storage devices.
-- Direct I/O is not supported on encrypted files. Attempts to use
- direct I/O on such files will fall back to buffered I/O.
+- Direct I/O is supported on encrypted files only under some
+ circumstances (see `Direct I/O support`_ for details). When these
+ circumstances are not met, attempts to use direct I/O on encrypted
+ files will fall back to buffered I/O.
- The fallocate operations FALLOC_FL_COLLAPSE_RANGE and
FALLOC_FL_INSERT_RANGE are not supported on encrypted files and will
@@ -1121,6 +1123,21 @@ It is not currently possible to backup and restore encrypted files
without the encryption key. This would require special APIs which
have not yet been implemented.
+Direct I/O support
+==================
+
+Direct I/O on encrypted files is supported through blk-crypto. In
+particular, this means the kernel must have CONFIG_BLK_INLINE_ENCRYPTION
+enabled, the filesystem must have had the 'inlinecrypt' mount option
+specified, and either hardware inline encryption must be present, or
+CONFIG_BLK_INLINE_ENCRYPTION_FALLBACK must have been enabled. Further,
+the length of any I/O must be aligned to the filesystem block size
+(*not* necessarily the same as the block device's block size). If any of
+these conditions isn't met, attempts to do direct I/O on an encrypted file
+will fall back to buffered I/O. However, there aren't any additional
+requirements on user buffer alignment (apart from those already present
+when using direct I/O on unencrypted files).
+
Encryption policy enforcement
=============================
--
2.29.2.299.gdc1121823c-goog
next prev parent reply other threads:[~2020-11-17 14:08 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-17 14:07 [PATCH v7 0/8] add support for direct I/O with fscrypt using blk-crypto Satya Tangirala
2020-11-17 14:07 ` [PATCH v7 1/8] block: ensure bios are not split in middle of crypto data unit Satya Tangirala
2020-11-17 23:31 ` Eric Biggers
2020-11-18 0:38 ` Satya Tangirala
2020-11-25 22:12 ` Eric Biggers
2020-12-02 22:52 ` Satya Tangirala
2020-11-25 22:15 ` Eric Biggers
2020-11-17 14:07 ` [PATCH v7 2/8] blk-crypto: don't require user buffer alignment Satya Tangirala
2020-11-17 23:51 ` Eric Biggers
2020-11-17 14:07 ` [PATCH v7 3/8] fscrypt: add functions for direct I/O support Satya Tangirala
2020-11-17 14:07 ` [PATCH v7 4/8] direct-io: add support for fscrypt using blk-crypto Satya Tangirala
2020-11-17 14:07 ` [PATCH v7 5/8] iomap: support direct I/O with " Satya Tangirala
2020-11-17 14:07 ` [PATCH v7 6/8] ext4: " Satya Tangirala
2020-12-03 13:45 ` Theodore Y. Ts'o
2020-11-17 14:07 ` [PATCH v7 7/8] f2fs: " Satya Tangirala
2020-11-17 14:07 ` Satya Tangirala [this message]
2020-11-18 2:38 ` [PATCH v7 8/8] fscrypt: update documentation for direct I/O support Eric Biggers
2020-11-17 17:15 ` [PATCH v7 0/8] add support for direct I/O with fscrypt using blk-crypto Theodore Y. Ts'o
2020-11-17 17:20 ` Darrick J. Wong
2020-12-03 23:57 ` Satya Tangirala
2020-11-18 2:51 ` Eric Biggers
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