[PATCH v3 6/7] fscrypt: document inline encryption support

[Satya Tangirala <satyat@google.com>]

Update the fscrypt documentation file for inline encryption support.

Signed-off-by: Satya Tangirala <satyat@google.com>
---
 Documentation/filesystems/fscrypt.rst | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/Documentation/filesystems/fscrypt.rst b/Documentation/filesystems/fscrypt.rst
index f5d8b0303ddf..f3d87a1a0a7f 100644
--- a/Documentation/filesystems/fscrypt.rst
+++ b/Documentation/filesystems/fscrypt.rst
@@ -1204,6 +1204,18 @@ buffer.  Some filesystems, such as UBIFS, already use temporary
 buffers regardless of encryption.  Other filesystems, such as ext4 and
 F2FS, have to allocate bounce pages specially for encryption.
 
+Fscrypt is also able to use inline encryption hardware instead of the
+kernel crypto API for en/decryption of file contents.  When possible, and
+if directed to do so (by specifying the 'inlinecrypt' mount option for
+an ext4/F2FS filesystem), it adds encryption contexts to bios and
+uses blk-crypto to perform the en/decryption instead of making use
+of the above read/write path changes.  Of course, even if directed to make
+use of inline encryption, fscrypt will only be able to do so if either
+hardware inline encryption support is available for the selected encryption
+algorithm or CONFIG_BLK_INLINE_ENCRYPTION_FALLBACK is selected.  If neither
+is the case, fscrypt will fall back to using the above mentioned read/write
+path changes for en/decryption.
+
 Filename hashing and encoding
 -----------------------------
 
@@ -1250,7 +1262,9 @@ Tests
 
 To test fscrypt, use xfstests, which is Linux's de facto standard
 filesystem test suite.  First, run all the tests in the "encrypt"
-group on the relevant filesystem(s).  For example, to test ext4 and
+group on the relevant filesystem(s).  One can also run the tests
+with the 'inlinecrypt' mount option to test the implementation for
+inline encryption support.  For example, to test ext4 and
 f2fs encryption using `kvm-xfstests
 <https://github.com/tytso/xfstests-bld/blob/master/Documentation/kvm-quickstart.md>`_::
 
-- 
2.28.0.rc0.105.gf9edc3c819-goog