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Kui-Feng Lee says:
====================
The subsystems managing struct_ops objects may need to detach a
struct_ops object due to errors or other reasons. It would be useful
to notify user space programs so that error recovery or logging can be
carried out.
This patch set enables the detach feature for struct_ops links and
send an event to epoll when a link is detached. Subsystems could call
link->ops->detach() to detach a link and notify user space programs
through epoll.
The signatures of callback functions in "struct bpf_struct_ops" have
been changed as well to pass an extra link argument to
subsystems. Subsystems could detach the links received from reg() and
update() callbacks if there is. This also provides a way that
subsystems can distinguish registrations for an object that has been
registered multiple times for several links.
However, bpf struct_ops maps without BPF_F_LINK have no any link.
Subsystems will receive NULL link pointer for this case.
---
Changes from v6:
- Fix the missing header at patch 5.
- Move RCU_INIT_POINTER() back to its original position.
Changes from v5:
- Change the commit title of the patch for bpftool.
Changes from v4:
- Change error code for bpf_struct_ops_map_link_update()
- Always return 0 for bpf_struct_ops_map_link_detach()
- Hold update_mutex in bpf_struct_ops_link_create()
- Add a separated instance of file_operations for links supporting
poll.
- Fix bpftool for bpf_link_fops_poll.
Changes from v3:
- Add a comment to explain why holding update_mutex is not necessary
in bpf_struct_ops_link_create()
- Use rcu_access_pointer() in bpf_struct_ops_map_link_poll().
Changes from v2:
- Rephrased commit logs and comments.
- Addressed some mistakes from patch splitting.
- Replace mutex with spinlock in bpf_testmod.c to address lockdep
Splat and simplify the implementation.
- Fix an argument passing to rcu_dereference_protected().
Changes from v1:
- Pass a link to reg, unreg, and update callbacks.
- Provide a function to detach a link from underlying subsystems.
- Add a kfunc to mimic detachments from subsystems, and provide a
flexible way to control when to do detachments.
- Add two tests to detach a link from the subsystem after the refcount
of the link drops to zero.
v6: https://lore.kernel.org/bpf/20240524223036.318800-1-thinker.li@gmail.com/
v5: https://lore.kernel.org/all/20240523230848.2022072-1-thinker.li@gmail.com/
v4: https://lore.kernel.org/all/20240521225121.770930-1-thinker.li@gmail.com/
v3: https://lore.kernel.org/all/20240510002942.1253354-1-thinker.li@gmail.com/
v2: https://lore.kernel.org/all/20240507055600.2382627-1-thinker.li@gmail.com/
v1: https://lore.kernel.org/all/20240429213609.487820-1-thinker.li@gmail.com/
====================
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.