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Plugin for importing VFS content
This new vfs_import plugin allows a VFS instance to be populated during construction using a sub-VFS configured in an '<import>' configuration node. This allows the ram_fs File_system server to be replaced by the VFS server by reimplementing the ram_fs 'content' feature. At the moment the copying of symlinks is not enabled, and the resources obtained by the import file-system may not be freed after the import is finished. Fix #2906
This commit is contained in:
Emery Hemingway
committed by
Christian Helmuth
Christian Helmuth
parent
f6c47a46c6
commit
59ac5b10c7
298
repos/gems/src/lib/vfs/import/plugin.cc
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298
repos/gems/src/lib/vfs/import/plugin.cc
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/*
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* \brief VFS content initialization/import plugin
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* \author Emery Hemingway
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* \date 2018-07-05
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*/
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/*
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* Copyright (C) 2018 Genode Labs GmbH
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*
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* This file is part of the Genode OS framework, which is distributed
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* under the terms of the GNU Affero General Public License version 3.
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*/
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#include <gems/vfs.h>
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#include <vfs/print.h>
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#include <base/heap.h>
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namespace Vfs_import {
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using namespace Vfs;
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class Flush_guard;
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class File_system;
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using Genode::Directory;
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using Genode::Root_directory;
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}
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/**
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* Utility to flush or sync a handle upon
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* leaving scope. Use with caution, syncing
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* may block for I/O signals.
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*/
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class Vfs_import::Flush_guard
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{
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private:
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Genode::Entrypoint &_ep;
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Vfs_handle &_handle;
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public:
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Flush_guard(Vfs::Env &env, Vfs_handle &handle)
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: _ep(env.env().ep()), _handle(handle) { }
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~Flush_guard()
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{
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while (true) {
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if ((_handle.fs().queue_sync(&_handle))
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&& (_handle.fs().complete_sync(&_handle)
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== Vfs::File_io_service::SYNC_OK))
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break;
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_ep.wait_and_dispatch_one_io_signal();
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}
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}
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};
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class Vfs_import::File_system : public Vfs::File_system
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{
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private:
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/**
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* XXX: A would-be temporary heap, but
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* deconstructing a VFS is not supported.
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*/
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Genode::Heap _heap;
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enum { CREATE_IT = true };
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static void copy_symlink(Vfs::Env &env,
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Root_directory &src,
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Directory::Path const &path,
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Genode::Allocator &alloc,
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bool overwrite)
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{
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Directory::Path target = src.read_symlink(path);
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Vfs_handle *dst_handle = nullptr;
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auto res = env.root_dir().openlink(
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path.string(), true, &dst_handle, alloc);
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if (res == OPENLINK_ERR_NODE_ALREADY_EXISTS && overwrite) {
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res = env.root_dir().openlink(
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path.string(), false, &dst_handle, alloc);
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}
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if (res != OPENLINK_OK) {
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if (res != OPENLINK_ERR_NODE_ALREADY_EXISTS)
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Genode::warning("skipping copy of symlink ", path, ", ", res);
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return;
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}
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Vfs_handle::Guard guard(dst_handle);
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{
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Flush_guard flush(env, *dst_handle);
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file_size count = target.length();
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for (;;) {
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file_size out_count = 0;
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auto wres = dst_handle->fs().write(
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dst_handle, target.string(), count, out_count);
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switch (wres) {
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case WRITE_ERR_AGAIN:
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case WRITE_ERR_WOULD_BLOCK:
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break;
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default:
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if (out_count < count) {
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Genode::error("failed to write symlink ", path, ", ", wres);
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env.root_dir().unlink(path.string());
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}
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return;
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}
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}
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}
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}
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static void copy_file(Vfs::Env &env,
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Root_directory &src,
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Directory::Path const &path,
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Genode::Allocator &alloc,
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bool overwrite)
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{
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using Genode::Readonly_file;
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Readonly_file src_file(src, path);
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Vfs_handle *dst_handle = nullptr;
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enum {
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WRITE = OPEN_MODE_WRONLY,
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CREATE = OPEN_MODE_WRONLY | OPEN_MODE_CREATE
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};
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auto res = env.root_dir().open(
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path.string(), CREATE , &dst_handle, alloc);
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if (res == OPEN_ERR_EXISTS && overwrite) {
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res = env.root_dir().open(
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path.string(), WRITE, &dst_handle, alloc);
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}
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if (res != OPEN_OK) {
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Genode::warning("skipping copy of file ", path, ", ", res);
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return;
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}
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Vfs_handle::Guard guard(dst_handle);
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{
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char buf[4096];
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Flush_guard flush(env, *dst_handle);
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Readonly_file::At at { };
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while (true) {
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file_size wn = 0;
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file_size rn = src_file.read(at, buf, sizeof(buf));
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if (!rn) break;
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auto wres = dst_handle->fs().write(dst_handle, buf, rn, wn);
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switch (wres) {
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case WRITE_OK:
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case WRITE_ERR_AGAIN:
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case WRITE_ERR_WOULD_BLOCK:
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break;
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default:
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Genode::error("failed to write to ", path, ", ", wres);
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env.root_dir().unlink(path.string());
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return;
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}
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dst_handle->advance_seek(wn);
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at.value += wn;
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}
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}
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}
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static void copy_dir(Vfs::Env &env,
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Root_directory &src,
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Directory::Path const &path,
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Genode::Allocator &alloc,
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bool overwrite)
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{
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{
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Vfs_handle *dir_handle = nullptr;
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env.root_dir().opendir(
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path.string(), CREATE_IT, &dir_handle, alloc);
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if (dir_handle)
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dir_handle->close();
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}
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{
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Directory dir(src, path);
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dir.for_each_entry([&] (Directory::Entry const &e) {
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auto entry_path = Directory::join(path, e.name());
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switch (e.type()) {
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case DIRENT_TYPE_FILE:
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copy_file(env, src, entry_path, alloc, overwrite);
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break;
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case DIRENT_TYPE_DIRECTORY:
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copy_dir(env, src, entry_path, alloc, overwrite);
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break;
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case DIRENT_TYPE_SYMLINK:
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copy_symlink(env, src, entry_path, alloc, overwrite);
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break;
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default:
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Genode::warning("skipping copy of ", e);
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break;
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}
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});
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}
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}
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public:
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File_system(Vfs::Env &env, Genode::Xml_node config)
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: _heap(env.env().pd(), env.env().rm())
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{
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bool overwrite = config.attribute_value("overwrite", false);
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Root_directory content(env.env(), _heap, config);
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copy_dir(env, content, Directory::Path(""), _heap, overwrite);
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}
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const char* type() override { return "import"; }
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/***********************
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** Directory service **
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***********************/
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Genode::Dataspace_capability dataspace(char const*) override {
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return Genode::Dataspace_capability(); }
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void release(char const*, Dataspace_capability) override { }
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Open_result open(const char*, unsigned, Vfs::Vfs_handle**, Genode::Allocator&) override {
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return Open_result::OPEN_ERR_UNACCESSIBLE; }
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Opendir_result opendir(char const*, bool,
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Vfs_handle**, Allocator&) override {
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return OPENDIR_ERR_LOOKUP_FAILED; }
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void close(Vfs::Vfs_handle*) override { }
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Stat_result stat(const char*, Vfs::Directory_service::Stat&) override {
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return STAT_ERR_NO_ENTRY; }
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Unlink_result unlink(const char*) override { return UNLINK_ERR_NO_ENTRY; }
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Rename_result rename(const char*, const char*) override {
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return RENAME_ERR_NO_ENTRY; }
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file_size num_dirent(const char*) override {
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return 0; }
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bool directory(char const*) override {
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return false; }
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const char* leaf_path(const char *) override {
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return nullptr; }
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/**********************
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** File I/O service **
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**********************/
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Write_result write(Vfs_handle*,
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const char *, file_size,
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file_size &) override {
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return WRITE_ERR_INVALID; }
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Read_result complete_read(Vfs_handle*,
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char*, file_size,
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file_size&) override {
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return READ_ERR_INVALID; }
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bool read_ready(Vfs_handle*) override {
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return true; }
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bool notify_read_ready(Vfs_handle*) override {
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return false; }
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Ftruncate_result ftruncate(Vfs_handle*, file_size) override {
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return FTRUNCATE_ERR_NO_PERM; }
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Sync_result complete_sync(Vfs_handle*) override {
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return SYNC_OK; }
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};
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extern "C" Vfs::File_system_factory *vfs_file_system_factory(void)
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{
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struct Factory : Vfs::File_system_factory
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{
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Vfs::File_system *create(Vfs::Env &env, Genode::Xml_node config) override
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{
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return new (env.alloc())
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Vfs_import::File_system(env, config);
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}
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};
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static Factory f;
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return &f;
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}
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2
repos/gems/src/lib/vfs/import/target.mk
Normal file
2
repos/gems/src/lib/vfs/import/target.mk
Normal file
@ -0,0 +1,2 @@
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TARGET = dummy-vfs_import
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LIBS = vfs_import
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