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Refactor cached_fs_rom

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Refactor the cached_fs_rom server to fix issues with packet congestion,
prevent recursive XML handling, and zero-length file handling.

Ref #2760
This commit is contained in:
Emery Hemingway 2018-07-12 17:49:56 +02:00 committed by Christian Helmuth
parent b7e95c1525
commit d00baf8db4
2 changed files with 243 additions and 226 deletions
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1
repos/os/recipes/src/cached_fs_rom/used_apis
View File

@ -1,3 +1,4 @@
base
file_system_session
os
report_session

462
repos/os/src/server/cached_fs_rom/main.cc
View File

@ -12,6 +12,7 @@
*/
/* Genode includes */
#include <os/reporter.h>
#include <os/path.h>
#include <file_system_session/connection.h>
#include <file_system/util.h>
@ -36,49 +37,130 @@ namespace Cached_fs_rom {
typedef Genode::Path<File_system::MAX_PATH_LEN> Path;
typedef File_system::Session_client::Tx::Source Tx_source;
class Rom_file;
typedef Genode::Id_space<Rom_file> Rom_files;
struct Cached_rom;
typedef Genode::Id_space<Cached_rom> Cache_space;
struct Transfer;
typedef Genode::Id_space<Transfer> Transfer_space;
class Session_component;
typedef Genode::Id_space<Session_component> Sessions;
typedef Genode::Id_space<Session_component> Session_space;
struct Packet_handler;
struct Main;
typedef File_system::Session::Tx::Source::Packet_alloc_failed Packet_alloc_failed;
typedef File_system::File_handle File_handle;
}
class Cached_fs_rom::Rom_file final
struct Cached_fs_rom::Cached_rom final
{
private:
Cached_rom(Cached_rom const &);
Cached_rom &operator = (Cached_rom const &);
Genode::Env &env;
Rm_connection &rm_connection;
size_t const file_size;
/**
* Backing RAM dataspace
*/
Attached_ram_dataspace ram_ds { env.pd(), env.rm(), file_size };
/**
* Read-only region map exposed as ROM module to the client
*/
Region_map_client rm { rm_connection.create(ram_ds.size()) };
Region_map::Local_addr rm_attachment { };
Dataspace_capability rm_ds { };
Path const path;
Cache_space::Element cache_elem;
Transfer *transfer = nullptr;
/**
* Reference count of cache entry
*/
int _ref_count = 0;
Cached_rom(Cache_space &cache_space,
Env &env,
Rm_connection &rm,
Path const &file_path,
size_t size)
:
env(env), rm_connection(rm), file_size(size),
path(file_path),
cache_elem(*this, cache_space)
{ }
/**
* Destructor
*/
~Cached_rom()
{
if (rm_attachment)
rm.detach(rm_attachment);
}
bool completed() const { return rm_ds.valid(); }
bool unused() const { return (_ref_count < 1); }
void complete()
{
/* attach dataspace read-only into region map */
enum { OFFSET = 0, LOCAL_ADDR = false, EXEC = true, WRITE = false };
rm_attachment = rm.attach(
ram_ds.cap(), file_size, OFFSET,
LOCAL_ADDR, (addr_t)~0, EXEC, WRITE);
rm_ds = rm.dataspace();
}
/**
* Return dataspace with content of file
*/
Rom_dataspace_capability dataspace() const {
return static_cap_cast<Rom_dataspace>(rm_ds); }
struct Guard
{
Cached_rom &_rom;
Guard(Cached_rom &rom) : _rom(rom) {
++_rom._ref_count; }
~Guard() {
--_rom._ref_count; };
};
void report(Reporter::Xml_generator &xml) const
{
xml.node("cache", [&] () {
xml.attribute("path", path.string());
xml.attribute("ref", _ref_count);
xml.attribute("size", file_size);
xml.attribute("ready", completed());
});
}
};
struct Cached_fs_rom::Transfer final
{
Cached_rom &_cached_rom;
Cached_rom::Guard _cache_guard { _cached_rom };
Env &_env;
Rm_connection &_rm_connection;
File_system::Session &_fs;
File_system::File_handle _handle;
Rom_files &_roms;
Constructible<Rom_files::Element> _roms_elem { };
File_system::file_size_t const _size;
File_system::seek_off_t _seek = 0;
File_system::Packet_descriptor _raw_pkt = _alloc_packet();
File_system::Packet_guard _packet_guard { *_fs.tx(), _raw_pkt };
/**
* Name of requested file, interpreted at path into the file system
*/
Path const _file_path;
/**
* Handle of associated file opened during read loop
*/
Constructible<File_system::File_handle> _file_handle { };
/**
* Size of file
*/
File_system::file_size_t const _file_size;
/**
* Read offset of file handle
*/
File_system::seek_off_t _file_seek = 0;
Transfer_space::Element _transfer_elem;
/**
* Allocate space in the File_system packet buffer
@ -87,41 +169,21 @@ class Cached_fs_rom::Rom_file final
*/
File_system::Packet_descriptor _alloc_packet()
{
size_t chunk_size = min(_file_size, _fs.tx()->bulk_buffer_size()/4);
if (!_fs.tx()->ready_to_submit())
throw Packet_alloc_failed();
size_t chunk_size = min(_size, _fs.tx()->bulk_buffer_size()/4);
return _fs.tx()->alloc_packet(chunk_size);
}
/**
* Packet space used by this session
*/
File_system::Packet_descriptor _raw_pkt = _alloc_packet();
/**
* Dataspace to read into
*/
Attached_ram_dataspace _file_ds { _env.pd(), _env.rm(), (size_t)_file_size };
/**
* Read-only region map exposed as ROM module to the client
*/
Region_map_client _rm { _rm_connection.create(_file_ds.size()) };
Region_map::Local_addr _rm_attachment { };
Dataspace_capability _rm_ds { };
/**
* Reference count of ROM file, initialize to one and
* decrement after read completes.
*/
int _ref_count = 1;
void _submit_next_packet()
{
using namespace File_system;
File_system::Packet_descriptor
packet(_raw_pkt, *_file_handle,
packet(_raw_pkt, _handle,
File_system::Packet_descriptor::READ,
_raw_pkt.size(), _file_seek);
_raw_pkt.size(), _seek);
_fs.tx()->submit_packet(packet);
}
@ -130,97 +192,58 @@ class Cached_fs_rom::Rom_file final
/**
* Constructor
*
* \param fs file-system session to read the file from
* \param filename requested file name
* \param sig_rec signal receiver used to get notified about changes
* within the compound directory (in the case when
* the requested file could not be found at session-
* creation time)
*/
Rom_file(Env &env,
Rm_connection &rm,
Transfer(Transfer_space &space,
Cached_rom &rom,
File_system::Session &fs,
File_system::File_handle handle,
size_t size,
Rom_files &cache,
Path const &file_path)
File_system::File_handle file_handle,
size_t file_size)
:
_env(env), _rm_connection(rm), _fs(fs), _roms(cache),
_file_path(file_path), _file_size(size)
_cached_rom(rom), _fs(fs),
_handle(file_handle), _size(file_size),
_transfer_elem(*this, space, Transfer_space::Id{_handle.value})
{
/*
* invert the file handle id to push the element to
* the opposite end of the space
*/
_roms_elem.construct(*this, _roms, Rom_files::Id{~handle.value});
_file_handle.construct(handle);
_cached_rom.transfer = this;
_submit_next_packet();
}
/**
* Destructor
*/
~Rom_file()
{
if (_file_handle.constructed())
_fs.close(*_file_handle);
_fs.tx()->release_packet(_raw_pkt);
Path const &path() const { return _cached_rom.path; }
if (_rm_attachment)
_rm.detach(_rm_attachment);
}
Path const &path() const { return _file_path; }
bool completed() const { return _rm_ds.valid(); }
void inc_ref() { ++_ref_count; }
void dec_ref() { --_ref_count; }
bool unused() const { return (_ref_count < 1); }
bool completed() const { return (_seek >= _size); }
/**
* Return dataspace with content of file
*/
Rom_dataspace_capability dataspace() const {
return static_cap_cast<Rom_dataspace>(_rm_ds); }
/**
* Called from the signal handler.
* Called from the packet signal handler.
*/
void process_packet(File_system::Packet_descriptor const packet)
{
if (packet.position() != _file_seek || _file_seek >= _file_size) {
error("bad packet seek position for ", _file_path, "!");
throw ~0;
auto const pkt_seek = packet.position();
if (pkt_seek > _seek || _seek >= _size) {
error("bad packet seek position for ", path());
error("packet seek is ", packet.position(), ", file seek is ", _seek, ", file size is ", _size);
_seek = _size;
} else {
size_t const n = min(packet.length(), _file_size - _file_seek);
memcpy(_file_ds.local_addr<char>()+_file_seek,
size_t const n = min(packet.length(), _size - pkt_seek);
memcpy(_cached_rom.ram_ds.local_addr<char>()+pkt_seek,
_fs.tx()->packet_content(packet), n);
_file_seek += n;
_seek = pkt_seek+n;
}
if (_file_seek >= _file_size) {
_fs.tx()->release_packet(_raw_pkt);
_fs.close(*_file_handle);
_file_handle.destruct();
_roms_elem.destruct();
_roms_elem.construct(*this, _roms);
--_ref_count;
/* attach dataspace read-only into region map */
enum { OFFSET = 0, LOCAL_ADDR = false, EXEC = true, WRITE = false };
_rm_attachment = _rm.attach(
_file_ds.cap(), _file_size, OFFSET,
LOCAL_ADDR, (addr_t)~0, EXEC, WRITE);
_rm_ds = _rm.dataspace();
} else {
if (completed())
_cached_rom.complete();
else
_submit_next_packet();
}
void report(Reporter::Xml_generator &xml) const
{
xml.node("transfer", [&] () {
xml.attribute("path", path().string());
xml.attribute("pkt_size", _raw_pkt.size());
xml.attribute("seek", _seek);
xml.attribute("size", _size);
});
}
};
@ -229,25 +252,28 @@ class Cached_fs_rom::Session_component final : public Rpc_object<Rom_session>
{
private:
Rom_file &_rom_file;
Sessions::Element _sessions_elem;
Cached_rom &_cached_rom;
Cached_rom::Guard _cache_guard { _cached_rom };
Session_space::Element _sessions_elem;
Session_label const _label;
public:
Session_component(Rom_file &rom_file,
Sessions &sessions,
Sessions::Id id)
Session_component(Cached_rom &cached_rom,
Session_space &space, Session_space::Id id,
Session_label const &label)
:
_rom_file(rom_file),
_sessions_elem(*this, sessions, id)
{
_rom_file.inc_ref();
}
_cached_rom(cached_rom),
_sessions_elem(*this, space, id),
_label(label)
{ }
~Session_component()
void report(Reporter::Xml_generator &xml) const
{
_rom_file.dec_ref();
xml.node("session", [&] () {
xml.attribute("id", _sessions_elem.id().value);
xml.attribute("label", _label.string());
});
}
/***************************
@ -255,9 +281,10 @@ class Cached_fs_rom::Session_component final : public Rpc_object<Rom_session>
***************************/
Rom_dataspace_capability dataspace() override {
return _rom_file.dataspace(); }
return _cached_rom.dataspace(); }
void sigh(Signal_context_capability) override { }
bool update() override { return false; }
};
@ -266,17 +293,16 @@ struct Cached_fs_rom::Main final : Genode::Session_request_handler
{
Genode::Env &env;
Reporter reporter { env, "state", "state", 1<<20 };
Rm_connection rm { env };
Rom_files rom_cache { };
Sessions rom_sessions { };
Cache_space cache { };
Transfer_space transfers { };
Session_space sessions { };
/* Heap for local allocation */
Heap heap { env.pd(), env.rm() };
/* allocate sessions on a simple heap */
Sliced_heap sliced_heap { env.pd(), env.rm() };
Allocator_avl fs_tx_block_alloc { &heap };
File_system::Connection fs { env, fs_tx_block_alloc };
@ -285,23 +311,33 @@ struct Cached_fs_rom::Main final : Genode::Session_request_handler
Io_signal_handler<Main> packet_handler {
env.ep(), *this, &Main::handle_packets };
void report_state()
{
if (!reporter.enabled()) return;
Reporter::Xml_generator xml(reporter, [&] () {
cache.for_each<Cached_rom&>([&] (Cached_rom &rom) {
rom.report(xml); });
transfers.for_each<Transfer&>([&] (Transfer &transfer) {
transfer.report(xml); });
sessions.for_each<Session_component&>([&] (Session_component &session) {
session.report(xml); });
});
}
/**
* Return true when a cache element is freed
*/
bool cache_evict()
{
Rom_file *discard = nullptr;
Cached_rom *discard = nullptr;
rom_cache.for_each<Rom_file&>([&] (Rom_file &rf) {
if (discard) return;
if (rf.unused()) discard = &rf;
});
cache.for_each<Cached_rom&>([&] (Cached_rom &rom) {
if (!discard && rom.unused()) discard = &rom; });
if (discard) {
if (discard)
destroy(heap, discard);
return true;
}
return false;
return (bool)discard;
}
/**
@ -366,85 +402,70 @@ struct Cached_fs_rom::Main final : Genode::Session_request_handler
** Find ROM in cache **
***********************/
Session_space::Id const id { pid.value };
Session_label const label = label_from_args(args.string());
Path const path(label.last_element().string());
Sessions::Id const id { pid.value };
Rom_file *rom_file = nullptr;
Cached_rom *rom = nullptr;
/* lookup the Rom_file in the cache */
rom_cache.for_each<Rom_file&>([&] (Rom_file &rf) {
if (!rom_file && rf.path() == path)
rom_file = &rf;
/* lookup the ROM in the cache */
cache.for_each<Cached_rom&>([&] (Cached_rom &other) {
if (!rom && other.path == path)
rom = &other;
});
if (!rom_file) {
if (!fs.tx()->ready_to_submit()) {
Genode::warning("File_system packet queue is congested, defering read of ", path);
return;
}
if (!rom) {
File_system::File_handle handle = try_open(path);
File_system::Handle_guard guard(fs, handle);
size_t file_size = fs.status(handle).size;
/* alloc-or-evict loop */
do {
try {
new (heap)
Rom_file(env, rm, fs, handle, file_size, rom_cache, path);
/* session is ready when read completes */
return;
}
catch (Packet_alloc_failed) {
Genode::warning("File_system packet buffer is congested, defering read of ", path);
fs.close(handle);
return;
}
/*
* There is an assumption that failure to allocate
* will implicitly trigger a resource request to the
* parent. If this behavior changes in the base library
* then this local mechanism cannot be expected to work.
*/
catch (Quota_guard<Ram_quota>::Limit_exceeded) { }
catch (Quota_guard<Cap_quota>::Limit_exceeded) { }
} while (cache_evict());
/* eviction failed */
warning("insufficient resources for '", label, "'"
", stalling for upgrade");
fs.close(handle);
return;
if (file_size == 0) {
error("unable to serve zero-length file \"", path, "\"");
throw Service_denied();
}
if (!rom_file->completed())
return;
while (env.pd().avail_ram().value < file_size || env.pd().avail_caps().value < 8) {
/* drop unused cache entries */
if (!cache_evict()) break;
}
rom = new (heap) Cached_rom(cache, env, rm, path, file_size);
report_state();
}
/***************************
** Create new RPC object **
***************************/
try {
Session_component *session = new (sliced_heap)
Session_component(*rom_file, rom_sessions, id);
if (rom->completed()) {
/* Create new RPC object */
Session_component *session = new (heap)
Session_component(*rom, sessions, id, label);
env.parent().deliver_session_cap(pid, env.ep().manage(*session));
}
report_state();
catch (Sessions::Conflicting_id) {
Genode::warning("session request handled twice, ", args);
} else if (!rom->transfer) {
File_system::File_handle handle = try_open(path);
try { new (heap) Transfer(transfers, *rom, fs, handle, rom->file_size); }
catch (...) {
Genode::warning("defer transfer of ", rom->path);
/* retry when next pending transfer completes */
return;
}
report_state();
}
}
void handle_session_close(Parent::Server::Id pid) override
{
Sessions::Id id { pid.value };
rom_sessions.apply<Session_component&>(
Session_space::Id id { pid.value };
sessions.apply<Session_component&>(
id, [&] (Session_component &session)
{
env.ep().dissolve(session);
destroy(sliced_heap, &session);
destroy(heap, &session);
env.parent().session_response(pid, Parent::SESSION_CLOSED);
});
report_state();
}
void handle_packets()
@ -458,12 +479,14 @@ struct Cached_fs_rom::Main final : Genode::Session_request_handler
bool stray_pkt = true;
/* find the appropriate session */
rom_cache.apply<Rom_file&>(
Rom_files::Id{~(pkt.handle().value)}, [&] (Rom_file &rom)
transfers.apply<Transfer&>(
Transfer_space::Id{pkt.handle().value}, [&] (Transfer &transfer)
{
rom.process_packet(pkt);
if (rom.completed())
transfer.process_packet(pkt);
if (transfer.completed()) {
session_requests.schedule();
destroy(heap, &transfer);
}
stray_pkt = false;
});
@ -474,13 +497,13 @@ struct Cached_fs_rom::Main final : Genode::Session_request_handler
Main(Genode::Env &env) : env(env)
{
/* process the requests when more resources are made available */
env.parent().resource_avail_sigh(session_requests);
fs.sigh_ack_avail(packet_handler);
/* process any requests that have already queued */
session_requests.schedule();
try { reporter.enabled(true); }
catch (...) { log("state report disabled"); }
}
};
@ -489,11 +512,4 @@ void Component::construct(Genode::Env &env)
{
static Cached_fs_rom::Main inst(env);
env.parent().announce("ROM");
/**
* XXX This workaround can be removed with the eager creation of the
* the env log session.
*/
Genode::log("--- cached_fs_rom ready ---");
}