[PATCH v2 0/2] ovl: allow O_PATH file descriptor when specifying layers

[Christian Brauner <brauner@kernel.org>]

Allow overlayfs to use O_PATH file descriptors when specifying layers.
Userspace must currently use non-O_PATH file desriptors which is often
pointless especially if the file descriptors have been created via
open_tree(OPEN_TREE_CLONE). This has been a frequent request and came up
again in [1].

Link: https://lore.kernel.org/r/fd8f6574-f737-4743-b220-79c815ee1554@mbaynton.com [1]

Signed-off-by: Christian Brauner <brauner@kernel.org>
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Changes in v2:
- Unconditionally enable O_PATH file descriptors.
- Link to v1: https://lore.kernel.org/r/20250207-work-overlayfs-v1-0-611976e73373@kernel.org

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Christian Brauner (2):
      fs: support O_PATH fds with FSCONFIG_SET_FD
      selftests/overlayfs: test specifying layers as O_PATH file descriptors

 fs/autofs/autofs_i.h                               |  2 +
 fs/fsopen.c                                        |  2 +-
 .../filesystems/overlayfs/set_layers_via_fds.c     | 65 ++++++++++++++++++++++
 3 files changed, 68 insertions(+), 1 deletion(-)
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base-commit: 2014c95afecee3e76ca4a56956a936e23283f05b
change-id: 20250207-work-overlayfs-38fb9156d4c4