pidfs: implement file handle support

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On 64-bit platforms, userspace can read the pidfd's inode in order to
get a never-repeated PID identifier. On 32-bit platforms this identifier
is not exposed, as inodes are limited to 32 bits. Instead expose the
identifier via export_fh, which makes it available to userspace via
name_to_handle_at.

In addition we implement fh_to_dentry, which allows userspace to
recover a pidfd from a pidfs file handle.

Signed-off-by: Erin Shepherd <erin.shepherd@e43.eu>
[brauner: patch heavily rewritten]
Link: https://lore.kernel.org/r/20241129-work-pidfs-file_handle-v1-6-87d803a42495@kernel.org
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Co-Developed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>

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Christian Brauner 2024-11-29 14:38:05 +01:00

parent c220e216d6

commit b3caba8f7a

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fs/pidfs.c

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