Merge pull request #1237 from trapexit/threadfix

Initialize readdir threadpool after daemonizing

Makefile

@@ -42,7 +42,7 @@ UGID_USE_RWLOCK = 0
 ifeq ($(DEBUG),1)
 OPT_FLAGS := -O0 -g -fsanitize=undefined
 else
-OPT_FLAGS := -O2
+OPT_FLAGS := -O2 -DNDEBUG
 endif
 
 ifeq ($(STATIC),1)

man/mergerfs.1

@@ -391,7 +391,9 @@ to enable page caching for when \f[C]cache.files=per-process\f[R].
 .IP \[bu] 2
 \f[B]parallel-direct-writes=BOOL\f[R]: Allow the kernel to dispatch
 multiple, parallel (non-extending) write requests for files opened with
-\f[C]direct_io=true\f[R] (if supported by the kernel)
+\f[C]cache.files=per-process\f[R] (if the process is not in
+\f[C]process-names\f[R]) or \f[C]cache.files=off\f[R].
+(This requires kernel support, and was added in v6.2)
 .IP \[bu] 2
 \f[B]direct_io\f[R]: deprecated - Bypass page cache.
 Use \f[C]cache.files=off\f[R] instead.
@@ -859,8 +861,8 @@ calculations.
 The reason is that it doesn\[cq]t really work for non-path preserving
 policies and can lead to non-obvious behaviors.
 .PP
-NOTE: While any policy can be assigned to a function or category though
-some may not be very useful in practice.
+NOTE: While any policy can be assigned to a function or category, some
+may not be very useful in practice.
 For instance: \f[B]rand\f[R] (random) may be useful for file creation
 (create) but could lead to very odd behavior if used for \f[C]chmod\f[R]
 if there were more than one copy of the file.
@@ -1753,9 +1755,12 @@ size are unchanged since previous open.
 cache.files=libfuse: follow traditional libfuse \f[C]direct_io\f[R],
 \f[C]kernel_cache\f[R], and \f[C]auto_cache\f[R] arguments.
 .IP \[bu] 2
-cache.files=per-process: Enable page caching only for processes which
-`comm' name matches one of the values defined in
+cache.files=per-process: Enable page caching (equivalent to
+\f[C]cache.files=partial\f[R]) only for processes whose `comm' name
+matches one of the values defined in
 \f[C]cache.files.process-names\f[R].
+If the name does not match the file open is equivalent to
+\f[C]cache.files=off\f[R].
 .PP
 FUSE, which mergerfs uses, offers a number of page caching modes.
 mergerfs tries to simplify their use via the \f[C]cache.files\f[R]

src/fuse_init.cpp

@@ -137,6 +137,8 @@ namespace FUSE
 
     ugid::init();
 
+    cfg->readdir.initialize();
+
     l::want_if_capable(conn_,FUSE_CAP_ASYNC_DIO);
     l::want_if_capable(conn_,FUSE_CAP_ASYNC_READ,&cfg->async_read);
     l::want_if_capable(conn_,FUSE_CAP_ATOMIC_O_TRUNC);

src/fuse_readdir.cpp

@@ -17,10 +17,15 @@
 */
 
 #include "fuse_readdir.hpp"
-#include "fuse_readdir_factory.hpp"
 
 #include "config.hpp"
+#include "fuse_readdir_factory.hpp"
 
+/*
+  The _initialized stuff is not pretty but easiest way to deal with
+  the fact that mergerfs is doing arg parsing and setting up of things
+  (including thread pools) before the daemonizing
+ */
 
 int
 FUSE::readdir(const fuse_file_info_t *ffi_,
@@ -32,8 +37,10 @@ FUSE::readdir(const fuse_file_info_t *ffi_,
 }
 
 FUSE::ReadDir::ReadDir(std::string const s_)
+  : _initialized(false)
 {
   from_string(s_);
+  if(_initialized)
     assert(_readdir);
 }
 
@@ -45,9 +52,18 @@ FUSE::ReadDir::to_string() const
   return _type;
 }
 
+void
+FUSE::ReadDir::initialize()
+{
+  _initialized = true;
+  from_string(_type);
+}
+
 int
 FUSE::ReadDir::from_string(std::string const &str_)
 {
+  if(_initialized)
+    {
       std::shared_ptr<FUSE::ReadDirBase> tmp;
 
       tmp = FUSE::ReadDirFactory::make(str_);
@@ -58,12 +74,24 @@ FUSE::ReadDir::from_string(std::string const &str_)
         std::lock_guard<std::mutex> lg(_mutex);
 
         _type    = str_;
-    _readdir = tmp;
+        std::swap(_readdir,tmp);
+      }
+    }
+  else
+    {
+      std::lock_guard<std::mutex> lg(_mutex);
+
+      _type = str_;
     }
 
   return 0;
 }
 
+/*
+  Yeah... if not initialized it will crash... ¯\_(ツ)_/¯
+  This will be resolved once initialization of internal objects and
+  handling of input is better seperated.
+*/
 int
 FUSE::ReadDir::operator()(fuse_file_info_t const *ffi_,
                           fuse_dirents_t         *buf_)

src/fuse_readdir.hpp

@@ -25,7 +25,10 @@
 
 #include <assert.h>
 
-
+// The initialization behavior is not pretty but for the moment
+// needed due to the daemonizing function of the libfuse library when
+// not using foreground mode. The threads need to be created after the
+// fork, not before.
 namespace FUSE
 {
   int readdir(fuse_file_info_t const *ffi,
@@ -44,10 +47,14 @@ namespace FUSE
     int operator()(fuse_file_info_t const *ffi,
                    fuse_dirents_t         *buf);
 
+  public:
+    void initialize();
+
   private:
     mutable std::mutex _mutex;
 
   private:
+    bool _initialized;
     std::string _type;
     std::shared_ptr<FUSE::ReadDirBase> _readdir;
   };

src/unbounded_thread_pool.hpp

@@ -2,6 +2,8 @@
 
 #include "unbounded_queue.hpp"
 
+#include "syslog.hpp"
+
 #include <atomic>
 #include <csignal>
 #include <functional>
@@ -21,8 +23,13 @@ public:
   ThreadPool(std::size_t const thread_count_ = std::thread::hardware_concurrency(),
              std::string const name_         = {})
     : _queues(thread_count_),
-      _count(thread_count_)
+      _count(thread_count_),
+      _name(name_)
   {
+    syslog_info("threadpool: spawning %zu threads named '%s'",
+                _count,
+                _name.c_str());
+
     auto worker = [this](std::size_t i)
     {
       while(true)
@@ -51,10 +58,10 @@ public:
     _threads.reserve(thread_count_);
     for(std::size_t i = 0; i < thread_count_; ++i)
       _threads.emplace_back(worker, i);
-    if(!name_.empty())
+    if(!_name.empty())
       {
         for(auto &t : _threads)
-          pthread_setname_np(t.native_handle(),name_.c_str());
+          pthread_setname_np(t.native_handle(),_name.c_str());
       }
 
     pthread_sigmask(SIG_SETMASK,&oldset,NULL);
@@ -62,6 +69,10 @@ public:
 
   ~ThreadPool()
   {
+    syslog_info("threadpool: destroying %zu threads named '%s'",
+                _count,
+                _name.c_str());
+
     for(auto& queue : _queues)
       queue.unblock();
     for(auto& thread : _threads)
@@ -133,8 +144,9 @@ private:
   std::vector<std::thread> _threads;
 
 private:
-  const std::size_t _count;
+  std::size_t const _count;
   std::atomic_uint  _index;
+  std::string const _name;
 
   static const unsigned int K = 2;
 };