These patches extend FUSE to be able to act as a stacked filesystem. This allows pure passthrough, where the fuse file system simply reflects the lower filesystem, and also allows optional pre and post filtering in BPF and/or the userspace daemon as needed. This can dramatically reduce or even eliminate transitions to and from userspace. Currently, we either set the backing file/bpf at mount time at the root level, or at lookup time, via an optional block added at the end of the lookup return call. The added lookup block contains an fd for the backing file/folder and bpf if necessary, or a signal to clear or inherit the parent values. We're looking into two options for extending this to mkdir/mknod/etc, as we currently only support setting the backing to a pre-existing file, although naturally you can create new ones. When we're doing a lookup for create, we could pass an fd for the parent dir and the name of the backing file we're creating. This has the benefit of avoiding an additional call to userspace, but requires hanging on to some data in a negative dentry where there is no elegant place to store it. Another option is adding the same block we added to lookup to the create type op codes. This keeps that code more uniform, but means userspace must implement that logic in more areas. As is, the patches definitely need some work before they're ready. We still need to go through and ensure we respect changed filter values/disallow changes that don't make sense. We aren't currently calling mnt_want_write for the lower calls where appropriate, and we don't have an override_creds layer either. We also plan to add to our read/write iter filters to allow for more interesting use cases. There are also probably some node id inconsistencies. For nodes that will be completely passthrough, we give an id of 0. For the BPF verification side, we have currently set things set up in the old style, with a new bpf program type and helper functions. From LPC, my understanding is that newer bpf additions are done in a new style, so I imagine much of that will need to be redone as well, but hopefully these patches get across what our needs there are. For testing, we've provided the selftest code we have been using. We also have a mode to run with no userspace daemon in a pure passthrough mode that I have been running xfstests over to get some coverage on the backing operation code. I had to modify mounts/unmounts to get that running, along with some other small touch ups. The most notable failure I currently see there is in generic/126, which I suspect is likely related to override_creds. Alessio Balsini (1): fs: Generic function to convert iocb to rw flags Daniel Rosenberg (25): bpf: verifier: Allow for multiple packets bpf: verifier: Allow single packet invalidation fuse-bpf: Update uapi for fuse-bpf fuse-bpf: Add BPF supporting functions bpf: Export bpf_prog_fops fuse-bpf: Prepare for fuse-bpf patch fuse: Add fuse-bpf, a stacked fs extension for FUSE fuse-bpf: Don't support export_operations fuse-bpf: Partially add mapping support fuse-bpf: Add lseek support fuse-bpf: Add support for fallocate fuse-bpf: Support file/dir open/close fuse-bpf: Support mknod/unlink/mkdir/rmdir fuse-bpf: Add support for read/write iter fuse-bpf: support FUSE_READDIR fuse-bpf: Add support for sync operations fuse-bpf: Add Rename support fuse-bpf: Add attr support fuse-bpf: Add support for FUSE_COPY_FILE_RANGE fuse-bpf: Add xattr support fuse-bpf: Add symlink/link support fuse-bpf: allow mounting with no userspace daemon fuse-bpf: Call bpf for pre/post filters fuse-bpf: Add userspace pre/post filters fuse-bpf: Add selftests fs/fuse/Kconfig | 10 + fs/fuse/Makefile | 1 + fs/fuse/backing.c | 2753 +++++++++++++++++ fs/fuse/control.c | 2 +- fs/fuse/dev.c | 33 +- fs/fuse/dir.c | 443 ++- fs/fuse/file.c | 125 +- fs/fuse/fuse_i.h | 804 ++++- fs/fuse/inode.c | 292 +- fs/fuse/ioctl.c | 2 +- fs/fuse/readdir.c | 22 + fs/fuse/xattr.c | 36 + fs/overlayfs/file.c | 23 +- include/linux/bpf.h | 4 + include/linux/bpf_fuse.h | 64 + include/linux/bpf_types.h | 4 + include/linux/bpf_verifier.h | 5 +- include/linux/fs.h | 5 + include/uapi/linux/bpf.h | 33 + include/uapi/linux/fuse.h | 19 +- kernel/bpf/Makefile | 4 + kernel/bpf/bpf_fuse.c | 342 ++ kernel/bpf/btf.c | 1 + kernel/bpf/core.c | 5 + kernel/bpf/syscall.c | 1 + kernel/bpf/verifier.c | 144 +- tools/include/uapi/linux/bpf.h | 33 + tools/include/uapi/linux/fuse.h | 1066 +++++++ .../selftests/filesystems/fuse/.gitignore | 2 + .../selftests/filesystems/fuse/Makefile | 41 + .../testing/selftests/filesystems/fuse/OWNERS | 2 + .../selftests/filesystems/fuse/bpf_loader.c | 798 +++++ .../testing/selftests/filesystems/fuse/fd.txt | 21 + .../selftests/filesystems/fuse/fd_bpf.c | 370 +++ .../selftests/filesystems/fuse/fuse_daemon.c | 294 ++ .../selftests/filesystems/fuse/fuse_test.c | 2147 +++++++++++++ .../selftests/filesystems/fuse/test_bpf.c | 800 +++++ .../filesystems/fuse/test_framework.h | 173 ++ .../selftests/filesystems/fuse/test_fuse.h | 328 ++ 39 files changed, 11017 insertions(+), 235 deletions(-) create mode 100644 fs/fuse/backing.c create mode 100644 include/linux/bpf_fuse.h create mode 100644 kernel/bpf/bpf_fuse.c create mode 100644 tools/include/uapi/linux/fuse.h create mode 100644 tools/testing/selftests/filesystems/fuse/.gitignore create mode 100644 tools/testing/selftests/filesystems/fuse/Makefile create mode 100644 tools/testing/selftests/filesystems/fuse/OWNERS create mode 100644 tools/testing/selftests/filesystems/fuse/bpf_loader.c create mode 100644 tools/testing/selftests/filesystems/fuse/fd.txt create mode 100644 tools/testing/selftests/filesystems/fuse/fd_bpf.c create mode 100644 tools/testing/selftests/filesystems/fuse/fuse_daemon.c create mode 100644 tools/testing/selftests/filesystems/fuse/fuse_test.c create mode 100644 tools/testing/selftests/filesystems/fuse/test_bpf.c create mode 100644 tools/testing/selftests/filesystems/fuse/test_framework.h create mode 100644 tools/testing/selftests/filesystems/fuse/test_fuse.h base-commit: bf682942cd26ce9cd5e87f73ae099b383041e782 -- 2.37.3.998.g577e59143f-goog
