[RFC PATCH v3 0/8] fuse: LOOKUP_HANDLE operation

[Luis Henriques <luis@igalia.com>]

Hi,

I'm sending a new version of my work on lookup_handle, even though it's
still incomplete.  As suggested elsewhere, it is now based on compound
commands and thus it sits on top of Horst's patchset [0].  Also, because
this version is a complete re-write of the approach presented in my previous
RFC [1] I'm not going to detail what changed.

Here's a few notes:

- The code isn't yet fully testable as there are several pieces missing.
  For example, the FUSE_TMPFILE and FUSE_READDIRPLUS operations are not yet
  implemented.  The NFS-related changes have also been dropped in this
  revision.

- There are several details still to be sorted out in the compound
  operations.  For example, the nodeid for the statx operation in the
  lookup+statx is set to FUSE_ROOT_ID.

- The second operation (mkobj_handle+statx+open) is still draft (or maybe
  just wrong!).  It's not handling flags correctly, and the error handling
  has to be better thought out.

- Some of the patches in this set could probably be picked independently
  (e.g. patch 4 or even patch 1)

So, why am I sending this broken and incomplete patchset?  Well, simply
because I'd feel more confidence getting this approach validated.  I don't
expect any through review, but I would appreciate feedback on anything that
would help me correct major flaws.

[0] https://lore.kernel.org/all/20260210-fuse-compounds-upstream-v5-0-ea0585f62daa@ddn.com
[1] https://lore.kernel.org/all/20251212181254.59365-1-luis@igalia.com

Cheers,
-- 
Luis

Luis Henriques (8):
  fuse: simplify fuse_lookup_name() interface
  fuse: export extend_arg() and factor out fuse_ext_size()
  fuse: store index of the variable length argument
  fuse: drop unnecessary argument from fuse_lookup_init()
  fuse: extract helper functions from fuse_do_statx()
  fuse: implementation of lookup_handle+statx compound operation
  fuse: export fuse_open_args_fill() helper function
  fuse: implementation of mkobj_handle+statx+open compound operation

 fs/fuse/compound.c        |   1 +
 fs/fuse/cuse.c            |   1 +
 fs/fuse/dev.c             |   4 +-
 fs/fuse/dir.c             | 650 +++++++++++++++++++++++++++++++++-----
 fs/fuse/file.c            |   3 +-
 fs/fuse/fuse_i.h          |  42 ++-
 fs/fuse/inode.c           |  50 ++-
 fs/fuse/ioctl.c           |   1 +
 fs/fuse/readdir.c         |   2 +-
 fs/fuse/virtio_fs.c       |   6 +-
 fs/fuse/xattr.c           |   2 +
 include/uapi/linux/fuse.h |  25 +-
 12 files changed, 679 insertions(+), 108 deletions(-)