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. For this patch set, I have removed the code related to the bpf side of things since that is undergoing some large reworks to get it in line with the more recent BPF developements. This set of patches implements direct passthrough to the lower filesystem with no alteration. Looking at the v1 code should give a pretty good idea of what the general shape of the bpf calls will look like. Without the bpf side, it's like a less efficient bind mount. Not very useful on its own, but still useful to get eyes on it since the backing calls will be larglely the same when bpf is in the mix. This changes the format of adding a backing file/bpf slightly from v1. It's now a bit more modular. You add a block of data at the end of a lookup response to give the bpf fd and backing id, but there is now a type header to both blocks, and a reserved value for future additions. In the future, we may allow for multiple bpfs or backing files, and this will allow us to extend it without any UAPI breaking changes. Multiple BPFs would be useful for combining fuse-bpf implementations without needing to manually combine bpf fragments. Multiple backing files would allow implementing things like a limited overlayfs. In this patch set, this is only a single block, with only backing supported, although I've left the definitions reflecting the BPF case as well. For bpf, the plan is to have two blocks, with the bpf one coming first. Any further extensions are currently just speculative. You can run this without needing to set up a userspace daemon by adding these mount options: root_dir=[fd],no_daemon where fd is an open file descriptor pointing to the folder you'd like to use as the root directory. The fd can be immediately closed after mounting. This is useful for running various fs tests. The main changes for v2: -Refactored code to remove many of the ifdefs -Adjusted attr related code per Amir's suggestions -Added ioctl interface for responding to fuse requests (required for backing) -Adjusted lookup add-on block for adding backing file/bpf -Moved bpf related patches to the end of the stack (not included currently) TODO: override_creds to interact with backing files in the same context the daemon would Implement backing calls for other FUSE operations (i.e. File Locking/tmp files) Convert BPF over to more modern version Alessio Balsini (1): fs: Generic function to convert iocb to rw flags Daniel Rosenberg (20): fuse-bpf: Update fuse side uapi fuse-bpf: Prepare for fuse-bpf patch fuse: Add fuse-bpf, a stacked fs extension for FUSE fuse-bpf: Add ioctl interface for /dev/fuse fuse-bpf: Don't support export_operations fuse-bpf: Add support for FUSE_ACCESS 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 fs/fuse/Kconfig | 8 + fs/fuse/Makefile | 1 + fs/fuse/backing.c | 3118 +++++++++++++++++++++++++++++++++++++ fs/fuse/control.c | 2 +- fs/fuse/dev.c | 83 +- fs/fuse/dir.c | 326 ++-- fs/fuse/file.c | 62 +- fs/fuse/fuse_i.h | 424 ++++- fs/fuse/inode.c | 264 +++- fs/fuse/ioctl.c | 2 +- fs/fuse/readdir.c | 5 + fs/fuse/xattr.c | 18 + fs/overlayfs/file.c | 23 +- include/linux/fs.h | 5 + include/uapi/linux/fuse.h | 24 +- 15 files changed, 4154 insertions(+), 211 deletions(-) create mode 100644 fs/fuse/backing.c base-commit: 23a60a03d9a9980d1e91190491ceea0dc58fae62 -- 2.38.1.584.g0f3c55d4c2-goog
