On Fri, Jan 05, 2018 at 12:40:09PM -0800, Jaegeuk Kim wrote: > On 01/05, Eric Biggers wrote: > > From: Eric Biggers <ebiggers@xxxxxxxxxx> > > > > fscrypt_dummy_context_enabled() accesses ->s_cop, which now is only set > > when the filesystem is built with encryption support. This didn't > > actually matter because no filesystems called it. However, it will > > start being used soon, so fix it by moving it from fscrypt.h to > > fscrypt_supp.h and stubbing it out in fscrypt_notsupp.h. > > Ted, do we have a chance to get rid of this dummy_context? If there exists > backward compatibility issue, please never mind tho. > It's used to implement the test_dummy_encryption mount option for ext4, which is used by the 'ext4/encrypt' config for gce-xfstests. Its purpose is to cause all new files (directories, regular files, and symlinks) to be automatically encrypted with a default key, so that the encrypted I/O paths are tested more thoroughly than by just running the 'encrypt' group tests. There are no backward compatibility concerns with changing or removing the test_dummy_encryption mount option; we just don't have a better solution yet. Ideally, instead of using test_dummy_encryption we would encrypt the root directory of the filesystem immediately after it is formatted. However, that doesn't work for ext4 because the lost+found directory has to be located in the root directory, and must be unencrypted, and the lost+found directory entry must be unencrypted. So I think getting rid of test_dummy_encryption depends on a solution to the lost+found problem. An alternative would be to add support for "inherit-only" encryption policies, then set such a policy on the root directory of the filesystem. But, there haven't been any requests for such a feature yet outside of this specific testing-only use case, so I've been hesitant to add it. Eric
