Kernel+CrashDaemon: Use a ".partial" prefix for incomplete coredumps #26390
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The Kernel will now write to a .partial file until it is done writing, and then rename the file by removing the extension. This makes the final coredump appear atomically on the file system. So no need for special handling of partial files in CrashDaemon.
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| auto output_directory = KLexicalPath::dirname(coredump_path->view()); | ||
| auto vfs_root_context_root_custody = vfs_root_context()->root_custody().with([](auto& custody) -> NonnullRefPtr<Custody> { | ||
| return custody; | ||
| }); | ||
| auto dump_directory = TRY(VirtualFileSystem::open_directory(vfs_root_context(), credentials(), output_directory, *vfs_root_context_root_custody)); | ||
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| auto new_path = TRY(KString::try_create(coredump_path->view().trim(".partial"sv))); | ||
| TRY(VirtualFileSystem::rename(vfs_root_context(), credentials(), dump_directory, coredump_path->view(), dump_directory, new_path->view())); |
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The two CustodyBases rename expects are mapped to renameat(), so if the given paths are absolute, the dirfd/CustodyBase is ignored (see also https://github.com/LucasChollet/serenity/blob/824d5bf04ce331681895caf4eedbf520a21757e2/Kernel/FileSystem/VirtualFileSystem.cpp#L1086).
CustodyBase::resolve() returns the root custody if the given path is absolute, so I think you should be able to do that here as well. The coredump path should always be absolute, though we currently don't seem to check that when userspace writes the SysFS variable.
(side note: While looking at the CustodyBase class, I noticed that it's maybe a bit counterintuitive for it to store the path in the class itself rather than taking it as an argument for resolve())
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The Kernel will now write to a .partial file until it is done writing, and then rename the file by removing the extension.
This makes the final coredump appear atomically on the file system. So no need for special handling of partial files in CrashDaemon.