kernel: Make file system reference counting work for current directories

Also, make pipes usable again.

kernel/src/fs/VFS.h

@@ -15,9 +15,42 @@ namespace VFS
         Device
     };
 
-    class FileSystem;
     class Inode;
 
+    class FileSystem
+    {
+      public:
+        virtual SharedPtr<Inode> root_inode() const = 0;
+
+        virtual Result<SharedPtr<Inode>> create_file_inode() = 0;
+
+        virtual Result<SharedPtr<Inode>> create_dir_inode(SharedPtr<Inode> parent) = 0;
+
+        virtual Result<SharedPtr<Inode>> create_device_inode(u32 major, u32 minor) = 0;
+
+        virtual Result<void> set_mount_dir(SharedPtr<Inode> parent) = 0;
+
+        virtual u64 handles() const
+        {
+            return m_handles;
+        }
+
+        virtual void add_handle()
+        {
+            m_handles++;
+        }
+
+        virtual void remove_handle()
+        {
+            m_handles--;
+        }
+
+        virtual ~FileSystem() = default;
+
+      protected:
+        u64 m_handles { 0 };
+    };
+
     struct DirectoryEntry
     {
       public:
@@ -95,6 +128,18 @@ namespace VFS
         virtual InodeType type() const = 0;
 
         virtual usize inode_number() const = 0;
+
+        virtual void add_handle()
+        {
+            auto* f = fs();
+            if (f) f->add_handle();
+        }
+
+        virtual void remove_handle()
+        {
+            auto* f = fs();
+            if (f) f->remove_handle();
+        }
     };
 
     class FileInode : Inode
@@ -204,40 +249,6 @@ namespace VFS
         virtual ~DeviceInode() = default;
     };
 
-    class FileSystem
-    {
-      public:
-        virtual SharedPtr<Inode> root_inode() const = 0;
-
-        virtual Result<SharedPtr<Inode>> create_file_inode() = 0;
-
-        virtual Result<SharedPtr<Inode>> create_dir_inode(SharedPtr<Inode> parent) = 0;
-
-        virtual Result<SharedPtr<Inode>> create_device_inode(u32 major, u32 minor) = 0;
-
-        virtual Result<void> set_mount_dir(SharedPtr<Inode> parent) = 0;
-
-        virtual u64 handles() const
-        {
-            return m_handles;
-        }
-
-        virtual void add_handle()
-        {
-            m_handles++;
-        }
-
-        virtual void remove_handle()
-        {
-            m_handles--;
-        }
-
-        virtual ~FileSystem() = default;
-
-      protected:
-        u64 m_handles { 0 };
-    };
-
     Result<SharedPtr<Inode>> resolve_path(const char* path, Credentials auth,
                                           SharedPtr<VFS::Inode> working_directory = {});
 

kernel/src/sys/chdir.cpp

@@ -15,6 +15,9 @@ Result<u64> sys_chdir(Registers*, SyscallArgs args)
 
         if (inode->type() != VFS::InodeType::Directory) return err(ENOTDIR);
 
+        inode->add_handle();
+        if (current->current_directory) current->current_directory->remove_handle();
+
         current->current_directory = inode;
         current->current_directory_path = move(path);
 
@@ -30,6 +33,9 @@ Result<u64> sys_chdir(Registers*, SyscallArgs args)
 
         String new_path = TRY(PathParser::join(old_wdir.is_empty() ? "/"_sv : old_wdir, path.view()));
 
+        inode->add_handle();
+        if (current->current_directory) current->current_directory->remove_handle();
+
         current->current_directory = inode;
         current->current_directory_path = move(new_path);
 

kernel/src/sys/exec.cpp

@@ -90,7 +90,7 @@ Result<u64> sys_execve(Registers* regs, SyscallArgs args)
         if (!descriptor.has_value()) continue;
         if (descriptor->flags & O_CLOEXEC)
         {
-            descriptor->inode->fs()->remove_handle();
+            descriptor->inode->remove_handle();
             descriptor = {};
         }
     }
@@ -139,7 +139,7 @@ Result<u64> sys_fork(Registers* regs, SyscallArgs)
     for (int i = 0; i < FD_MAX; i++)
     {
         thread->fd_table[i] = current->fd_table[i];
-        if (current->fd_table[i].has_value()) current->fd_table[i]->inode->fs()->add_handle();
+        if (current->fd_table[i].has_value()) current->fd_table[i]->inode->add_handle();
     }
 
     image->apply(thread);

kernel/src/sys/open.cpp

@@ -72,7 +72,7 @@ Result<u64> sys_openat(Registers*, SyscallArgs args)
 
     kinfoln("openat: opening file %s from dirfd %d, flags %d, mode %#o = fd %d", path.chars(), dirfd, flags, mode, fd);
 
-    inode->fs()->add_handle();
+    inode->add_handle();
 
     current->fd_table[fd] = FileDescriptor { inode, 0, flags & FLAGS_TO_KEEP };
 
@@ -90,7 +90,7 @@ Result<u64> sys_close(Registers*, SyscallArgs args)
 
     if (!descriptor.has_value()) return err(EBADF);
 
-    descriptor->inode->fs()->remove_handle();
+    descriptor->inode->remove_handle();
 
     descriptor = {};
 

kernel/src/thread/Scheduler.cpp

@@ -185,7 +185,7 @@ namespace Scheduler
 
             for (int i = 0; i < FD_MAX; i++)
             {
-                if (thread->fd_table[i].has_value()) thread->fd_table[i]->inode->fs()->remove_handle();
+                if (thread->fd_table[i].has_value()) thread->fd_table[i]->inode->remove_handle();
             }
         }