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Yonghong Song says: ==================== Andrii raised a concern that current uapi for bpf iterator map element is a little restrictive and not suitable for future potential complex customization. This is a valid suggestion, considering people may indeed add more complex custimization to the iterator, e.g., cgroup_id + user_id, etc. for task or task_file. Another example might be map_id plus additional control so that the bpf iterator may bail out a bucket earlier if a bucket has too many elements which may hold lock too long and impact other parts of systems. Patch #1 modified uapi with kernel changes. Patch #2 adjusted libbpf api accordingly. Changelogs: v3 -> v4: . add a forward declaration of bpf_iter_link_info in tools/lib/bpf/bpf.h in case that libbpf is built against not-latest uapi bpf.h. . target the patch set to "bpf" instead of "bpf-next" v2 -> v3: . undo "not reject iter_info.map.map_fd == 0" from v1. In the future map_fd may become optional, so let us use map_fd == 0 indicating the map_fd is not set by user space. . add link_info_len to bpf_iter_attach_opts to ensure always correct link_info_len from user. Otherwise, libbpf may deduce incorrect link_info_len if it uses different uapi header than the user app. v1 -> v2: . ensure link_create target_fd/flags == 0 since they are not used. (Andrii) . if either of iter_info ptr == 0 or iter_info_len == 0, but not both, return error to user space. (Andrii) . do not reject iter_info.map.map_fd == 0, go ahead to use it trying to get a map reference since the map_fd is required for map_elem iterator. . use bpf_iter_link_info in bpf_iter_attach_opts instead of map_fd. this way, user space is responsible to set up bpf_iter_link_info and libbpf just passes the data to the kernel, simplifying libbpf design. (Andrii) ==================== Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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 Restructured Text 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.