[PATCH] generic/556: add a check to make sure ext4 supports encrypted casefolding

[PATCH] generic/556: add a check to make sure ext4 supports encrypted casefolding

[Theodore Ts'o]

Some older kernels support ext4 file systems with encryption enabled,
and with casefold enabled, but not file systems have both encryption
*and* casefolding enabled.  On those kernels, generic/556 will fail.
Fortunately, we can test if ext4 supports encrypted casefold via the
presence of /sys/fs/ext4/features/encrypted_casefold.

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
---
 common/casefold   | 17 +++++++++++++++++
 tests/generic/556 |  1 +
 2 files changed, 18 insertions(+)

diff --git a/common/casefold b/common/casefold
index 9172d818..7b76b986 100644
--- a/common/casefold
+++ b/common/casefold
@@ -43,6 +43,23 @@ _require_scratch_casefold()
 	_require_command "$LSATTR_PROG" lsattr
 }
 
+_require_encrypted_casefold ()
+{
+    case $FSTYP in
+	ext4)
+	    if test ! -f /sys/fs/ext4/features/casefold ; then
+		_notrun "casefolding not supported"
+	    fi
+	    if test ! -f /sys/fs/ext4/features/encryption ; then
+		_notrun "file system encryption not supported"
+	    fi
+	    if test ! -f /sys/fs/ext4/features/encrypted_casefold ; then
+		_notrun "encrypted casefolding not supported"
+	    fi
+	    ;;
+	esac
+}
+
 _scratch_mkfs_casefold()
 {
 	case $FSTYP in
diff --git a/tests/generic/556 b/tests/generic/556
index 3145188c..7916a08e 100755
--- a/tests/generic/556
+++ b/tests/generic/556
@@ -16,6 +16,7 @@ status=1 # failure is thea default
 . ./common/attr
 
 _supported_fs generic
+_require_encrypted_casefold
 _require_scratch_nocheck
 _require_scratch_casefold
 _require_symlinks
-- 
2.31.0

Re: [PATCH] generic/556: add a check to make sure ext4 supports encrypted casefolding

[Darrick J. Wong]

On Mon, Jun 21, 2021 at 12:49:01PM -0400, Theodore Ts'o wrote:
> Some older kernels support ext4 file systems with encryption enabled,
> and with casefold enabled, but not file systems have both encryption
> *and* casefolding enabled.  On those kernels, generic/556 will fail.
> Fortunately, we can test if ext4 supports encrypted casefold via the
> presence of /sys/fs/ext4/features/encrypted_casefold.
> 
> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
> ---
>  common/casefold   | 17 +++++++++++++++++
>  tests/generic/556 |  1 +
>  2 files changed, 18 insertions(+)
> 
> diff --git a/common/casefold b/common/casefold
> index 9172d818..7b76b986 100644
> --- a/common/casefold
> +++ b/common/casefold
> @@ -43,6 +43,23 @@ _require_scratch_casefold()
>  	_require_command "$LSATTR_PROG" lsattr
>  }
>  
> +_require_encrypted_casefold ()
> +{
> +    case $FSTYP in
> +	ext4)
> +	    if test ! -f /sys/fs/ext4/features/casefold ; then
> +		_notrun "casefolding not supported"
> +	    fi
> +	    if test ! -f /sys/fs/ext4/features/encryption ; then
> +		_notrun "file system encryption not supported"
> +	    fi
> +	    if test ! -f /sys/fs/ext4/features/encrypted_casefold ; then
> +		_notrun "encrypted casefolding not supported"

Dumb question: Are there kernels that support encrypted casefold but not
those two components separately?

--D

> +	    fi
> +	    ;;
> +	esac
> +}
> +
>  _scratch_mkfs_casefold()
>  {
>  	case $FSTYP in
> diff --git a/tests/generic/556 b/tests/generic/556
> index 3145188c..7916a08e 100755
> --- a/tests/generic/556
> +++ b/tests/generic/556
> @@ -16,6 +16,7 @@ status=1 # failure is thea default
>  . ./common/attr
>  
>  _supported_fs generic
> +_require_encrypted_casefold
>  _require_scratch_nocheck
>  _require_scratch_casefold
>  _require_symlinks
> -- 
> 2.31.0
> 

Re: [PATCH] generic/556: add a check to make sure ext4 supports encrypted casefolding

[Eric Biggers]

On Mon, Jun 21, 2021 at 12:49:01PM -0400, Theodore Ts'o wrote:
> diff --git a/tests/generic/556 b/tests/generic/556
> index 3145188c..7916a08e 100755
> --- a/tests/generic/556
> +++ b/tests/generic/556
> @@ -16,6 +16,7 @@ status=1 # failure is thea default
>  . ./common/attr
>  
>  _supported_fs generic
> +_require_encrypted_casefold

This isn't an encrypt+casefold test though, but rather just a casefold test.  It
only becomes an encrypt+casefold test when $MOUNT_OPTIONS includes
test_dummy_encryption.

I think we shouldn't update the test itself, but rather make
_require_scratch_casefold() call _require_encrypted_casefold() if
test_dummy_encryption is in $MOUNT_OPTIONS.

- Eric

Re: [PATCH] generic/556: add a check to make sure ext4 supports encrypted casefolding

[Eric Biggers]

On Mon, Jun 21, 2021 at 10:37:58AM -0700, Eric Biggers wrote:
> On Mon, Jun 21, 2021 at 12:49:01PM -0400, Theodore Ts'o wrote:
> > diff --git a/tests/generic/556 b/tests/generic/556
> > index 3145188c..7916a08e 100755
> > --- a/tests/generic/556
> > +++ b/tests/generic/556
> > @@ -16,6 +16,7 @@ status=1 # failure is thea default
> >  . ./common/attr
> >  
> >  _supported_fs generic
> > +_require_encrypted_casefold
> 
> This isn't an encrypt+casefold test though, but rather just a casefold test.  It
> only becomes an encrypt+casefold test when $MOUNT_OPTIONS includes
> test_dummy_encryption.
> 
> I think we shouldn't update the test itself, but rather make
> _require_scratch_casefold() call _require_encrypted_casefold() if
> test_dummy_encryption is in $MOUNT_OPTIONS.
> 

Hi Ted, just to follow up on this patch which never got merged:

I tried to reproduce the test failure with the 5.4 and 5.10 kernels, whose ext4
supported casefold but not encrypt+casefold.  However, it does *not* reproduce
with the "ext4/encrypt" configuration of kvm-xfstests, since
_require_scratch_casefold() already detects that the filesystem cannot mounted
with both the encrypt and casefold features:

        if ! _try_scratch_mount &>>seqres.full; then
                _notrun "kernel can't mount filesystem with the encoding set by userspace"
        fi

I think the problem is that you were running xfstests with test_dummy_encryption
but without adding "-O encrypt" to EXT_MKFS_OPTIONS.  That sort of works because
of the following code in __ext4_fill_super() in the kernel which force-enables
the encrypt feature if the test_dummy_encryption mount option was given:

	if (DUMMY_ENCRYPTION_ENABLED(sbi) && !sb_rdonly(sb) &&
	    !ext4_has_feature_encrypt(sb)) {
		ext4_set_feature_encrypt(sb);
		ext4_commit_super(sb);
	}

However, I don't think ext4 should be doing this.  The kernel should generally
not be messing with the feature flags, and this code can force-enable 'encrypt'
in cases where e2fsprogs would *not* allow it (e.g. the encrypt+casefold
situation being encountered here).  Also, f2fs doesn't allow this.

So I am planning to send a kernel patch to remove the above code from ext4.

- Eric