[PATCH 00/10] vfs: add O_CREAT|O_DIRECTORY to open*(2)

[Jori Koolstra]

This series implements new semantics for the O_CREAT|O_DIRECTORY flag
combination for open*(2): perform a mkdir and open the resulting
directory; return a pinning fd (which mkdir does not).

Most of the work happens in "vfs: add O_CREAT|O_DIRECTORY to open*(2),"
as may be expected. Before that there is some clean-up work and
preparation. The "vfs: short-circuit MAY_WRITE access for O_DIRECTORY
opens" patch is also worth paying extra attention to as it
short-circuits doomed opening of directories as writable. This check for
regular files is now done very late in do_open(), but for
O_CREAT|O_DIRECTORY this is unacceptable as this would create the
directory and then still fail.

Changes:
v3: https://lore.kernel.org/linux-fsdevel/20260704164149.3480051-1-jkoolstra@xxxxxxxxx/
   - address the inconsistency in calling audit_inode_child() in
     lookup_open() versus vfs_create() in a separate series.
   - fclog.c selftest header fix moved to separate patch.
   - add a "with trailing slash test" success test to the included
     selftests. 
   - pass struct qstr by pointer to trailing_slashes() and add a comment
     on what it does
   - changed commit message of "vfs: add O_CREAT|O_DIRECTORY to
     open*(2)" to address comments of Brauner

Jori Koolstra (10):
  fs/namei.c: use trailing_slashes()
  vfs: prepare vfs_creat|mkdir_no_perm for reuse in lookup_open()
  vfs: lookup_open(): move setting FMODE_CREATED down
  vfs: move ->create check in lookup_open() to before try_break_deleg()
  vfs: lookup_open(): use vfs_create_no_perm()
  vfs: add O_CREAT|O_DIRECTORY to open*(2)
  vfs: move O_IS_MKDIR check from lookup_open() into individual
    filesystems
  vfs: refuse O_CREAT for directories through a dangling symlink
  vfs: short-circuit MAY_WRITE access for O_DIRECTORY opens
  selftest: add tests for open*(O_CREAT|O_DIRECTORY)

 fs/9p/vfs_inode.c                             |   3 +
 fs/9p/vfs_inode_dotl.c                        |   3 +
 fs/ceph/file.c                                |   3 +
 fs/fuse/dir.c                                 |   3 +
 fs/gfs2/inode.c                               |   3 +
 fs/namei.c                                    | 224 ++++++++++++------
 fs/nfs/dir.c                                  |   6 +
 fs/open.c                                     |  32 ++-
 fs/smb/client/dir.c                           |   3 +
 fs/vboxsf/dir.c                               |   3 +
 include/linux/fcntl.h                         |   6 +
 .../testing/selftests/filesystems/.gitignore  |   1 +
 tools/testing/selftests/filesystems/Makefile  |   2 +-
 .../filesystems/open_o_creat_o_dir.c          | 201 ++++++++++++++++
 .../testing/selftests/filesystems/wrappers.h  |  11 +
 15 files changed, 419 insertions(+), 85 deletions(-)
 create mode 100644 tools/testing/selftests/filesystems/open_o_creat_o_dir.c

-- 
2.55.0