d456a33f04
Plaintext dentries are always valid, so only set fscrypt_d_ops on
ciphertext dentries.
Besides marginally improved performance, this allows overlayfs to use an
fscrypt-encrypted upperdir, provided that all the following are true:
(1) The fscrypt encryption key is placed in the keyring before
mounting overlayfs, and remains while the overlayfs is mounted.
(2) The overlayfs workdir uses the same encryption policy.
(3) No dentries for the ciphertext names of subdirectories have been
created in the upperdir or workdir yet. (Since otherwise
d_splice_alias() will reuse the old dentry with ->d_op set.)
One potential use case is using an ephemeral encryption key to encrypt
all files created or changed by a container, so that they can be
securely erased ("crypto-shredded") after the container stops.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.