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babf316409
Add bpf_link_new_file() API for cases when we need to ensure anon_inode is successfully created before we proceed with expensive BPF program attachment procedure, which will require equally (if not more so) expensive and potentially failing compensation detachment procedure just because anon_inode creation failed. This API allows to simplify code by ensuring first that anon_inode is created and after BPF program is attached proceed with fd_install() that can't fail. After anon_inode file is created, link can't be just kfree()'d anymore, because its destruction will be performed by deferred file_operations->release call. For this, bpf_link API required specifying two separate operations: release() and dealloc(), former performing detachment only, while the latter frees memory used by bpf_link itself. dealloc() needs to be specified, because struct bpf_link is frequently embedded into link type-specific container struct (e.g., struct bpf_raw_tp_link), so bpf_link itself doesn't know how to properly free the memory. In case when anon_inode file was successfully created, but subsequent BPF attachment failed, bpf_link needs to be marked as "defunct", so that file's release() callback will perform only memory deallocation, but no detachment. Convert raw tracepoint and tracing attachment to new API and eliminate detachment from error handling path. Signed-off-by: Andrii Nakryiko <andriin@fb.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: John Fastabend <john.fastabend@gmail.com> Link: https://lore.kernel.org/bpf/20200309231051.1270337-1-andriin@fb.com |
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