[PATCH v4 0/3] io_uring: add fremovexattr and flistxattr support

[Aditya Prakash Srivastava]

This series completes io_uring's FD-based xattr operations by adding
support for:
- IORING_OP_FREMOVEXATTR
- IORING_OP_FLISTXATTR

This allows asynchronous xattr removal and listing.

New test cases have been added to the liburing test suite
(test/xattr.c) and verified to pass. A separate userspace patch
implementing the matching prep helpers, sanitizers, and test cases
has been updated and submitted in parallel.

- Patch 1 syncs the tools/ directory's io_uring.h UAPI header to
  align it with kernel mainline prior to introducing the new opcodes.
- Patch 2 makes the necessary VFS-layer list/remove helpers
  non-static and declares them in fs/internal.h.
- Patch 3 implements the io_uring operational support (opcodes,
  opdefs, preparation, and issue handlers) and invokes these helpers.

Changes since v3:
- Split the tools/ UAPI header sync of pre-existing mainline opcodes
  into a separate precursor patch (Patch 1) (Suggested by Gabriel).
- Robustify io_fremovexattr_prep by initializing kname and kvalue
  to NULL to avoid potential garbage-pointer crashes in the
  io_xattr_cleanup path (Reported by Gabriel).
- Add strict validation to both fremovexattr and flistxattr to
  zero-check and reject all unused SQE fields (Reported by Gabriel).
- Reset ix->ctx.kname to NULL on error inside io_fremovexattr_prep.

Changes since v2:
- Revert unnecessary formatting changes to filename_listxattr in
  Patch 1 (now Patch 2).

Changes since v1:
- Omit path-based opcodes to prioritize optimal FD-based variants.
- Limit exported VFS helpers to only file_listxattr and
  file_removexattr.
- Rewrite standalone test program into a standard liburing testcase.

Aditya Prakash Srivastava (3):
  tools: sync io_uring.h UAPI header
  fs: make file_listxattr and file_removexattr helpers non-static
  io_uring: add fremovexattr and flistxattr support

 fs/internal.h                       |   2 +
 fs/xattr.c                          |   3 +-
 include/uapi/linux/io_uring.h       |   2 +
 io_uring/opdef.c                    |  18 ++
 io_uring/xattr.c                    |  83 +++++++
 io_uring/xattr.h                    |   6 +
 tools/include/uapi/linux/io_uring.h | 342 ++++++++++++++++++++++++++--
 7 files changed, 438 insertions(+), 18 deletions(-)

-- 
2.47.3