Add option to lazy umount target mount point

libfuse/lib/fuse_msgbuf.cpp

@@ -2,7 +2,6 @@
   ISC License
 
   Copyright (c) 2022, Antonio SJ Musumeci <trapexit@spawn.link>
-
   Permission to use, copy, modify, and/or distribute this software for any
   purpose with or without fee is hereby granted, provided that the above
   copyright notice and this permission notice appear in all copies.
@@ -22,6 +21,7 @@
 #include <fcntl.h>
 #include <unistd.h>
 
+#include <cstdlib>
 #include <mutex>
 #include <stack>
 

src/config.cpp

@@ -92,10 +92,11 @@ Config::Config()
     fuse_msg_size(FUSE_MAX_MAX_PAGES),
     ignorepponrename(false),
     inodecalc("hybrid-hash"),
+    lazy_umount_mountpoint(false),
     link_cow(false),
     link_exdev(LinkEXDEV::ENUM::PASSTHROUGH),
     log_metrics(false),
-    mount(),
+    mountpoint(),
     moveonenospc(false),
     nfsopenhack(NFSOpenHack::ENUM::OFF),
     nullrw(false),
@@ -160,11 +161,12 @@ Config::Config()
   _map["ignorepponrename"]       = &ignorepponrename;
   _map["inodecalc"]              = &inodecalc;
   _map["kernel_cache"]           = &kernel_cache;
+  _map["lazy-umount-mountpoint"] = &lazy_umount_mountpoint;
   _map["link_cow"]               = &link_cow;
   _map["link-exdev"]             = &link_exdev;
   _map["log.metrics"]            = &log_metrics;
   _map["minfreespace"]           = &minfreespace;
-  _map["mount"]                  = &mount;
+  _map["mount"]                  = &mountpoint;
   _map["moveonenospc"]           = &moveonenospc;
   _map["nfsopenhack"]            = &nfsopenhack;
   _map["nullrw"]                 = &nullrw;

src/config.hpp

@@ -121,10 +121,11 @@ public:
   ConfigBOOL     ignorepponrename;
   InodeCalc      inodecalc;
   ConfigBOOL     kernel_cache;
+  ConfigBOOL     lazy_umount_mountpoint;
   ConfigBOOL     link_cow;
   LinkEXDEV      link_exdev;
   LogMetrics     log_metrics;
-  ConfigSTR      mount;
+  ConfigSTR      mountpoint;
   MoveOnENOSPC   moveonenospc;
   NFSOpenHack    nfsopenhack;
   ConfigBOOL     nullrw;

src/fs_umount2.hpp

@@ -0,0 +1,49 @@
+/*
+  ISC License
+
+  Copyright (c) 2023, Antonio SJ Musumeci <trapexit@spawn.link>
+
+  Permission to use, copy, modify, and/or distribute this software for any
+  purpose with or without fee is hereby granted, provided that the above
+  copyright notice and this permission notice appear in all copies.
+
+  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+*/
+
+#pragma once
+
+#include <errno.h>
+#include <sys/mount.h>
+
+#include <string>
+
+namespace fs
+{
+  static
+  inline
+  int
+  umount2(const std::string target_,
+          const int         flags_)
+  {
+    int rv;
+
+    rv = ::umount2(target_.c_str(),
+                   flags_);
+
+    return ((rv == -1) ? -errno : rv);
+  }
+
+  static
+  inline
+  int
+  umount_lazy(const std::string target_)
+  {
+    return fs::umount2(target_,MNT_DETACH);
+  }
+}

src/fuse_link.cpp

@@ -326,7 +326,7 @@ namespace l
                                               st_,
                                               timeouts_);
       case LinkEXDEV::ENUM::ABS_POOL_SYMLINK:
-        return l::link_exdev_abs_pool_symlink(cfg_->mount,
+        return l::link_exdev_abs_pool_symlink(cfg_->mountpoint,
                                               oldpath_,
                                               newpath_,
                                               st_,

src/fuse_rename.cpp

@@ -358,7 +358,7 @@ namespace l
       case RenameEXDEV::ENUM::ABS_SYMLINK:
         return l::rename_exdev_abs_symlink(cfg_->func.rename.policy,
                                            cfg_->branches,
-                                           cfg_->mount,
+                                           cfg_->mountpoint,
                                            oldfusepath_,
                                            newfusepath_);
       }

src/mergerfs.cpp

@@ -18,6 +18,7 @@
 #include "syslog.hpp"
 
 #include "fs_path.hpp"
+#include "fs_umount2.hpp"
 #include "mergerfs.hpp"
 #include "option_parser.hpp"
 #include "resources.hpp"
@@ -162,7 +163,7 @@ namespace l
                 (uint64_t)cfg_->branches_mount_timeout);
 
     timeout = std::chrono::milliseconds(cfg_->branches_mount_timeout * 1000);
-    fs::wait_for_mount((std::string)cfg_->mount,
+    fs::wait_for_mount((std::string)cfg_->mountpoint,
                        paths,
                        timeout,
                        failed);
@@ -175,6 +176,32 @@ namespace l
                      failed.size());
   }
 
+  static
+  void
+  lazy_umount(const std::string target_)
+  {
+    int rv;
+
+    rv = fs::umount_lazy(target_);
+    switch(rv)
+      {
+      case 0:
+        syslog_notice("%s has been successfully lazily unmounted",
+                      target_.c_str());
+        break;
+      case -EINVAL:
+        syslog_notice("%s was not a mount point needing to be unmounted",
+                      target_.c_str());
+        break;
+      default:
+        syslog_error("Error unmounting %s: %d - %s",
+                     target_.c_str(),
+                     -rv,
+                     strerror(-rv));
+        break;
+      }
+  }
+
   int
   main(const int   argc_,
        char      **argv_)
@@ -205,6 +232,9 @@ namespace l
     l::setup_resources(cfg->scheduling_priority);
     l::get_fuse_operations(ops,cfg->nullrw);
 
+    if(cfg->lazy_umount_mountpoint)
+      l::lazy_umount(cfg->mountpoint);
+
     return fuse_main(args.argc,
                      args.argv,
                      &ops);

src/option_parser.cpp

@@ -378,7 +378,7 @@ check_for_mount_loop(Config::Write  &cfg_,
   fs::PathVector branches;
   std::error_code ec;
 
-  mount    = (std::string)cfg_->mount;
+  mount    = (std::string)cfg_->mountpoint;
   branches = cfg_->branches->to_paths();
   for(const auto &branch : branches)
     {
@@ -416,7 +416,7 @@ namespace options
 
     if(cfg->branches->empty())
       errs_->push_back({0,"branches not set"});
-    if(cfg->mount->empty())
+    if(cfg->mountpoint->empty())
       errs_->push_back({0,"mountpoint not set"});
 
     check_for_mount_loop(cfg,errs_);

src/syslog.cpp

@@ -73,6 +73,17 @@ syslog_info(const char *format_,
   va_end(valist);  
 }
 
+void
+syslog_notice(const char *format_,
+              ...)
+{
+  va_list valist;
+
+  va_start(valist,format_);
+  syslog_log(LOG_NOTICE,format_,valist);
+  va_end(valist);  
+}
+
 void
 syslog_warning(const char *format_,
                ...)

src/syslog.hpp

@@ -24,6 +24,7 @@
 void syslog_open();
 void syslog_log(const int priority, const char *format, ...);
 void syslog_info(const char *format, ...);
+void syslog_notice(const char *format, ...);
 void syslog_warning(const char *format, ...);
 void syslog_error(const char *format, ...);
 void syslog_close();