mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
synced 2026-08-28 07:33:45 -04:00
1d7443e4dc
Pull fscrypt updates from Eric Biggers:
"The main change this cycle is a significant simplification that's been
overdue for a while now: standardizing on a single file contents
encryption implementation in ext4 and f2fs, instead of having two.
Specifically, the original filesystem-layer file contents encryption
implementation is removed, and the blk-crypto implementation is now
used unconditionally. blk-crypto delegates either to inline crypto
hardware or to the CPU via blk-crypto-fallback. The latter is
functionally equivalent to the original filesystem-layer code.
The blk-crypto implementation already existed, but previously it was
used only when the filesystem was mounted with "-o inlinecrypt". Now,
"-o inlinecrypt" just selects whether inline crypto hardware is used.
To allow maintaining that user control over hardware use, the
blk-crypto API is extended with a new flag BLK_CRYPTO_CFG_ALLOW_HW.
Overall, this removes quite a bit of redundant code from ext4, f2fs,
and fs/crypto/. It should make things easier for ongoing filesystem
efforts such as iomap support, large folios, and btrfs encryption
(btrfs had already been planning to use blk-crypto exclusively.)
There are two small behavior changes of note:
- Direct I/O now works on encrypted files even without "-o inlinecrypt",
rather than falling back to buffered I/O. This is effectively a
bugfix, though I'll continue to keep an eye out for any user that
may have been depending on the buffered I/O fallback.
- IV_INO_LBLK_32 policies are no longer supported in certain cases
that didn't make sense and have no known uses.
This has been in linux-next since July 22 with no reported issues. All
encryption xfstests pass on ext4 and f2fs. As usual I've also been
using it on a system with an fscrypt-encrypted home directory. Of
course, the blk-crypto code paths also aren't new and were already
being used on many systems via the inlinecrypt mount option.
In addition to the main change described above, there are a few other
cleanups such as using lock guards for mutexes, improving
documentation, and removing a workaround for outdated gcc versions"
* tag 'fscrypt-for-linus' of git://git.kernel.org/pub/scm/fs/fscrypt/linux: (29 commits)
blk-crypto: Update docs for blk-crypto-fallback motivation
blk-crypto: Remove unused function blk_crypto_config_supported()
fscrypt: Update docs for data path
fscrypt: Remove unused function fscrypt_finalize_bounce_page()
f2fs: Update outdated comment in f2fs_write_begin()
fs: Update outdated comment for SB_INLINECRYPT
fscrypt: Update encryption policy version docs
fscrypt: Replace some variable-size memsets with fixed-size
fscrypt: Add safety checks to non-block-based en/decryption
fscrypt: Merge bio.c and inline_crypt.c into block.c
fscrypt: Remove unused functions and workqueue
fscrypt: Remove fs-layer zeroout code
fscrypt: Remove fscrypt_dio_supported()
fscrypt: Replace calls to fscrypt_inode_uses_inline_crypto()
fs/buffer: Remove fs-layer decryption code
f2fs: Remove fs-layer file contents en/decryption code
ext4: Further de-generalize the bio postprocessing code
ext4: Make ext4_bio_write_folio() return void
ext4: Remove fs-layer file contents en/decryption code
Documentation: fscrypt: Update docs for inlinecrypt
...
Why we want a copy of kernel headers in tools?
==============================================
There used to be no copies, with tools/ code using kernel headers
directly. From time to time tools/perf/ broke due to legitimate kernel
hacking. At some point Linus complained about such direct usage. Then we
adopted the current model.
The way these headers are used in perf are not restricted to just
including them to compile something.
There are sometimes used in scripts that convert defines into string
tables, etc, so some change may break one of these scripts, or new MSRs
may use some different #define pattern, etc.
E.g.:
$ ls -1 tools/perf/trace/beauty/*.sh | head -5
tools/perf/trace/beauty/arch_errno_names.sh
tools/perf/trace/beauty/drm_ioctl.sh
tools/perf/trace/beauty/fadvise.sh
tools/perf/trace/beauty/fsconfig.sh
tools/perf/trace/beauty/fsmount.sh
$
$ tools/perf/trace/beauty/fadvise.sh
static const char *fadvise_advices[] = {
[0] = "NORMAL",
[1] = "RANDOM",
[2] = "SEQUENTIAL",
[3] = "WILLNEED",
[4] = "DONTNEED",
[5] = "NOREUSE",
};
$
The tools/perf/check-headers.sh script, part of the tools/ build
process, points out changes in the original files.
So its important not to touch the copies in tools/ when doing changes in
the original kernel headers, that will be done later, when
check-headers.sh inform about the change to the perf tools hackers.
Another explanation from Ingo Molnar:
It's better than all the alternatives we tried so far:
- Symbolic links and direct #includes: this was the original approach but
was pushed back on from the kernel side, when tooling modified the
headers and broke them accidentally for kernel builds.
- Duplicate self-defined ABI headers like glibc: double the maintenance
burden, double the chance for mistakes, plus there's no tech-driven
notification mechanism to look at new kernel side changes.
What we are doing now is a third option:
- A software-enforced copy-on-write mechanism of kernel headers to
tooling, driven by non-fatal warnings on the tooling side build when
kernel headers get modified:
Warning: Kernel ABI header differences:
diff -u tools/include/uapi/drm/i915_drm.h include/uapi/drm/i915_drm.h
diff -u tools/include/uapi/linux/fs.h include/uapi/linux/fs.h
diff -u tools/include/uapi/linux/kvm.h include/uapi/linux/kvm.h
...
The tooling policy is to always pick up the kernel side headers as-is,
and integate them into the tooling build. The warnings above serve as a
notification to tooling maintainers that there's changes on the kernel
side.
We've been using this for many years now, and it might seem hacky, but
works surprisingly well.