Kernel: Don't copy a Vector<FileDescriptionAndFlags>

Instead of copying a Vector everytime we need to enumerate a Process'
file descriptions, we can just temporarily lock so it won't change.

28 files changed, 198 insertions, 128 deletions

diff --git a/Kernel/Process.cpp b/Kernel/Process.cpp
index 1ea0850b53..b6de160f0d 100644
--- a/Kernel/Process.cpp
+++ b/Kernel/Process.cpp
@@ -159,7 +159,7 @@ RefPtr<Process> Process::create_user_process(RefPtr<Thread>& first_thread, const
     auto process = Process::create(first_thread, parts.take_last(), uid, gid, parent_pid, false, move(cwd), nullptr, tty);
     if (!first_thread)
         return {};
-    if (!process->m_fds.try_resize(m_max_open_file_descriptors)) {
+    if (!process->m_fds.try_resize(process->m_fds.max_open())) {
         first_thread = nullptr;
         return {};
     }
@@ -393,42 +393,68 @@ RefPtr<Process> Process::from_pid(ProcessID pid)
     return {};
 }
 
-RefPtr<FileDescription> Process::file_description(int fd) const
+const Process::FileDescriptionAndFlags& Process::FileDescriptions::at(size_t i) const
+{
+    ScopedSpinLock lock(m_fds_lock);
+    return m_fds_metadatas[i];
+}
+Process::FileDescriptionAndFlags& Process::FileDescriptions::at(size_t i)
+{
+    ScopedSpinLock lock(m_fds_lock);
+    return m_fds_metadatas[i];
+}
+
+RefPtr<FileDescription> Process::FileDescriptions::file_description(int fd) const
 {
     ScopedSpinLock lock(m_fds_lock);
     if (fd < 0)
         return nullptr;
-    if (static_cast<size_t>(fd) < m_fds.size())
-        return m_fds[fd].description();
+    if (static_cast<size_t>(fd) < m_fds_metadatas.size())
+        return m_fds_metadatas[fd].description();
     return nullptr;
 }
 
-int Process::fd_flags(int fd) const
+int Process::FileDescriptions::fd_flags(int fd) const
 {
     ScopedSpinLock lock(m_fds_lock);
     if (fd < 0)
         return -1;
-    if (static_cast<size_t>(fd) < m_fds.size())
-        return m_fds[fd].flags();
+    if (static_cast<size_t>(fd) < m_fds_metadatas.size())
+        return m_fds_metadatas[fd].flags();
     return -1;
 }
 
-int Process::number_of_open_file_descriptors() const
+void Process::FileDescriptions::enumerate(Function<void(const FileDescriptionAndFlags&)> callback) const
 {
     ScopedSpinLock lock(m_fds_lock);
-    int count = 0;
-    for (size_t index = 0; index < m_fds.size(); index++) {
-        if (m_fds[index].is_valid())
-            ++count;
+    for (auto& file_description_metadata : m_fds_metadatas) {
+        callback(file_description_metadata);
+    }
+}
+
+void Process::FileDescriptions::change_each(Function<void(FileDescriptionAndFlags&)> callback)
+{
+    ScopedSpinLock lock(m_fds_lock);
+    for (auto& file_description_metadata : m_fds_metadatas) {
+        callback(file_description_metadata);
     }
+}
+
+size_t Process::FileDescriptions::open_count() const
+{
+    size_t count = 0;
+    enumerate([&](auto& file_description_metadata) {
+        if (file_description_metadata.is_valid())
+            ++count;
+    });
     return count;
 }
 
-int Process::alloc_fd(int first_candidate_fd)
+int Process::FileDescriptions::allocate(int first_candidate_fd)
 {
     ScopedSpinLock lock(m_fds_lock);
-    for (int i = first_candidate_fd; i < (int)m_max_open_file_descriptors; ++i) {
-        if (!m_fds[i])
+    for (size_t i = first_candidate_fd; i < max_open(); ++i) {
+        if (!m_fds_metadatas[i])
             return i;
     }
     return -EMFILE;
diff --git a/Kernel/Process.h b/Kernel/Process.h
index 5b1bc7bd65..69220fe7fe 100644
--- a/Kernel/Process.h
+++ b/Kernel/Process.h
@@ -228,9 +228,6 @@ public:
 
     bool in_group(gid_t) const;
 
-    RefPtr<FileDescription> file_description(int fd) const;
-    int fd_flags(int fd) const;
-
     // Breakable iteration functions
     template<IteratorFunction<Process&> Callback>
     static void for_each(Callback);
@@ -443,12 +440,6 @@ public:
     const Vector<String>& arguments() const { return m_arguments; };
     const Vector<String>& environment() const { return m_environment; };
 
-    int number_of_open_file_descriptors() const;
-    int max_open_file_descriptors() const
-    {
-        return m_max_open_file_descriptors;
-    }
-
     KResult exec(String path, Vector<String> arguments, Vector<String> environment, int recusion_depth = 0);
 
     KResultOr<LoadResult> load(NonnullRefPtr<FileDescription> main_program_description, RefPtr<FileDescription> interpreter_description, const ElfW(Ehdr) & main_program_header);
@@ -541,8 +532,6 @@ private:
 
     KResultOr<RefPtr<FileDescription>> find_elf_interpreter_for_executable(const String& path, const ElfW(Ehdr) & elf_header, int nread, size_t file_size);
 
-    int alloc_fd(int first_candidate_fd = 0);
-
     KResult do_kill(Process&, int signal);
     KResult do_killpg(ProcessGroupID pgrp, int signal);
     KResult do_killall(int signal);
@@ -586,8 +575,6 @@ private:
 
     OwnPtr<ThreadTracer> m_tracer;
 
-    static constexpr int m_max_open_file_descriptors { FD_SETSIZE };
-
 public:
     class FileDescriptionAndFlags {
         friend class FileDescriptionRegistrar;
@@ -616,14 +603,62 @@ public:
         InodeIndex m_global_procfs_inode_index;
     };
 
-    // FIXME: We create a copy when trying to iterate the Vector because
-    // we don't want to put lots of locking when accessing this Vector.
-    // Maybe try to encapsulate the Vector inside a protective class with locking
-    // mechanism.
-    Vector<FileDescriptionAndFlags> fds() const { return m_fds; }
+    class FileDescriptions {
+        friend class Process;
+
+    public:
+        ALWAYS_INLINE const FileDescriptionAndFlags& operator[](size_t i) const { return at(i); }
+        ALWAYS_INLINE FileDescriptionAndFlags& operator[](size_t i) { return at(i); }
+
+        FileDescriptions& operator=(const Kernel::Process::FileDescriptions& other)
+        {
+            ScopedSpinLock lock(m_fds_lock);
+            ScopedSpinLock lock_other(other.m_fds_lock);
+            m_fds_metadatas = other.m_fds_metadatas;
+            for (auto& file_description_metadata : m_fds_metadatas) {
+                file_description_metadata.refresh_inode_index();
+            }
+            return *this;
+        }
+
+        const FileDescriptionAndFlags& at(size_t i) const;
+        FileDescriptionAndFlags& at(size_t i);
+
+        void enumerate(Function<void(const FileDescriptionAndFlags&)>) const;
+        void change_each(Function<void(FileDescriptionAndFlags&)>);
+
+        int allocate(int first_candidate_fd = 0);
+        size_t open_count() const;
+
+        bool try_resize(size_t size) { return m_fds_metadatas.try_resize(size); }
+
+        size_t max_open() const
+        {
+            return m_max_open_file_descriptors;
+        }
+
+        void clear()
+        {
+            ScopedSpinLock lock(m_fds_lock);
+            m_fds_metadatas.clear();
+        }
+
+        // FIXME: Consider to remove this somehow
+        RefPtr<FileDescription> file_description(int fd) const;
+        int fd_flags(int fd) const;
+
+    private:
+        FileDescriptions() = default;
+        static constexpr size_t m_max_open_file_descriptors { FD_SETSIZE };
+        mutable SpinLock<u8> m_fds_lock;
+        Vector<FileDescriptionAndFlags> m_fds_metadatas;
+    };
+
+    FileDescriptions& fds() { return m_fds; }
+    const FileDescriptions& fds() const { return m_fds; }
 
 private:
-    Vector<FileDescriptionAndFlags> m_fds;
+    FileDescriptions m_fds;
 
     mutable RecursiveSpinLock m_thread_list_lock;
 
@@ -659,7 +694,6 @@ private:
 
     FutexQueues m_futex_queues;
     SpinLock<u8> m_futex_lock;
-    mutable SpinLock<u8> m_fds_lock;
 
     // This member is used in the implementation of ptrace's PT_TRACEME flag.
     // If it is set to true, the process will stop at the next execve syscall
diff --git a/Kernel/ProcessExposed.cpp b/Kernel/ProcessExposed.cpp
index e9f81aa91e..54ba651d24 100644
--- a/Kernel/ProcessExposed.cpp
+++ b/Kernel/ProcessExposed.cpp
@@ -454,7 +454,7 @@ private:
             process_object.add("uid", process.uid());
             process_object.add("gid", process.gid());
             process_object.add("ppid", process.ppid().value());
-            process_object.add("nfds", process.number_of_open_file_descriptors());
+            process_object.add("nfds", process.fds().open_count());
             process_object.add("name", process.name());
             process_object.add("executable", process.executable() ? process.executable()->absolute_path() : "");
             process_object.add("tty", process.tty() ? process.tty()->tty_name() : "notty");
@@ -1239,7 +1239,7 @@ private:
 KResultOr<size_t> ProcFSProcessFileDescriptions::entries_count() const
 {
     Locker locker(m_lock);
-    return m_process_folder->m_associated_process->number_of_open_file_descriptors();
+    return m_process_folder->m_associated_process->fds().open_count();
 }
 KResult ProcFSProcessFileDescriptions::traverse_as_directory(unsigned fsid, Function<bool(const FS::DirectoryEntryView&)> callback) const
 {
@@ -1248,29 +1248,36 @@ KResult ProcFSProcessFileDescriptions::traverse_as_directory(unsigned fsid, Func
     callback({ "..", { fsid, m_parent_folder->component_index() }, 0 });
 
     auto process = m_process_folder->m_associated_process;
-    for (int i = 0; i < process->max_open_file_descriptors(); ++i) {
-        auto description_metadata = process->fds()[i];
-        if (!description_metadata.is_valid())
-            continue;
-        InodeIdentifier identifier = { fsid, description_metadata.global_procfs_inode_index() };
-        callback({ String::number(i), identifier, 0 });
-    }
+    size_t count = 0;
+    m_process_folder->m_associated_process->fds().enumerate([&](auto& file_description_metadata) {
+        if (!file_description_metadata.is_valid()) {
+            count++;
+            return;
+        }
+        InodeIdentifier identifier = { fsid, file_description_metadata.global_procfs_inode_index() };
+        callback({ String::number(count), identifier, 0 });
+        count++;
+    });
     return KSuccess;
 }
 RefPtr<ProcFSExposedComponent> ProcFSProcessFileDescriptions::lookup(StringView name)
 {
     Locker locker(m_lock);
     auto process = m_process_folder->m_associated_process;
-    ScopedSpinLock lock(process->m_fds_lock);
-    for (int i = 0; i < process->max_open_file_descriptors(); ++i) {
-        auto description_metadata = process->fds()[i];
-        if (!description_metadata.is_valid())
-            continue;
-        if (name == String::number(i)) {
-            return ProcFSProcessFileDescription::create(i, *description_metadata.description(), description_metadata.global_procfs_inode_index(), *this);
+    RefPtr<ProcFSProcessFileDescription> procfd_fd;
+    // FIXME: Try to exit the loop earlier
+    size_t count = 0;
+    m_process_folder->m_associated_process->fds().enumerate([&](auto& file_description_metadata) {
+        if (!file_description_metadata.is_valid()) {
+            count++;
+            return;
         }
-    }
-    return nullptr;
+        if (name == String::number(count)) {
+            procfd_fd = ProcFSProcessFileDescription::create(count, *file_description_metadata.description(), file_description_metadata.global_procfs_inode_index(), *this);
+        }
+        count++;
+    });
+    return procfd_fd;
 }
 
 class ProcFSProcessUnveil final : public ProcFSProcessInformation {
@@ -1350,19 +1357,21 @@ private:
     {
         JsonArraySerializer array { builder };
         auto process = m_parent_folder->m_associated_process;
-        if (process->number_of_open_file_descriptors() == 0) {
+        if (process->fds().open_count() == 0) {
             array.finish();
             return true;
         }
 
-        for (int i = 0; i < process->max_open_file_descriptors(); ++i) {
-            auto description = process->file_description(i);
-            if (!description)
-                continue;
-            bool cloexec = process->fd_flags(i) & FD_CLOEXEC;
-
+        size_t count = 0;
+        process->fds().enumerate([&](auto& file_description_metadata) {
+            if (!file_description_metadata.is_valid()) {
+                count++;
+                return;
+            }
+            bool cloexec = file_description_metadata.flags() & FD_CLOEXEC;
+            RefPtr<FileDescription> description = file_description_metadata.description();
             auto description_object = array.add_object();
-            description_object.add("fd", i);
+            description_object.add("fd", count);
             description_object.add("absolute_path", description->absolute_path());
             description_object.add("seekable", description->file().is_seekable());
             description_object.add("class", description->file().class_name());
@@ -1371,7 +1380,9 @@ private:
             description_object.add("blocking", description->is_blocking());
             description_object.add("can_read", description->can_read());
             description_object.add("can_write", description->can_write());
-        }
+            count++;
+        });
+
         array.finish();
         return true;
     }
diff --git a/Kernel/Syscalls/anon_create.cpp b/Kernel/Syscalls/anon_create.cpp
index a7d56bad53..a0c57da8b7 100644
--- a/Kernel/Syscalls/anon_create.cpp
+++ b/Kernel/Syscalls/anon_create.cpp
@@ -24,7 +24,7 @@ KResultOr<FlatPtr> Process::sys$anon_create(size_t size, int options)
     if (size > NumericLimits<ssize_t>::max())
         return EINVAL;
 
-    int new_fd = alloc_fd();
+    int new_fd = m_fds.allocate();
     if (new_fd < 0)
         return new_fd;
 
diff --git a/Kernel/Syscalls/chdir.cpp b/Kernel/Syscalls/chdir.cpp
index 715cb94c97..6d69d91c07 100644
--- a/Kernel/Syscalls/chdir.cpp
+++ b/Kernel/Syscalls/chdir.cpp
@@ -27,7 +27,7 @@ KResultOr<FlatPtr> Process::sys$chdir(Userspace<const char*> user_path, size_t p
 KResultOr<FlatPtr> Process::sys$fchdir(int fd)
 {
     REQUIRE_PROMISE(stdio);
-    auto description = file_description(fd);
+    auto description = fds().file_description(fd);
     if (!description)
         return EBADF;
 
diff --git a/Kernel/Syscalls/chmod.cpp b/Kernel/Syscalls/chmod.cpp
index 366fb0f0cc..0e8be00b1e 100644
--- a/Kernel/Syscalls/chmod.cpp
+++ b/Kernel/Syscalls/chmod.cpp
@@ -23,7 +23,7 @@ KResultOr<FlatPtr> Process::sys$chmod(Userspace<const char*> user_path, size_t p
 KResultOr<FlatPtr> Process::sys$fchmod(int fd, mode_t mode)
 {
     REQUIRE_PROMISE(fattr);
-    auto description = file_description(fd);
+    auto description = fds().file_description(fd);
     if (!description)
         return EBADF;
     return description->chmod(mode);
diff --git a/Kernel/Syscalls/chown.cpp b/Kernel/Syscalls/chown.cpp
index 97d9e50e67..ddc0203aca 100644
--- a/Kernel/Syscalls/chown.cpp
+++ b/Kernel/Syscalls/chown.cpp
@@ -12,7 +12,7 @@ namespace Kernel {
 KResultOr<FlatPtr> Process::sys$fchown(int fd, uid_t uid, gid_t gid)
 {
     REQUIRE_PROMISE(chown);
-    auto description = file_description(fd);
+    auto description = fds().file_description(fd);
     if (!description)
         return EBADF;
     return description->chown(uid, gid);
diff --git a/Kernel/Syscalls/dup2.cpp b/Kernel/Syscalls/dup2.cpp
index 6539b288e6..87a17fbba9 100644
--- a/Kernel/Syscalls/dup2.cpp
+++ b/Kernel/Syscalls/dup2.cpp
@@ -12,12 +12,12 @@ namespace Kernel {
 KResultOr<FlatPtr> Process::sys$dup2(int old_fd, int new_fd)
 {
     REQUIRE_PROMISE(stdio);
-    auto description = file_description(old_fd);
+    auto description = fds().file_description(old_fd);
     if (!description)
         return EBADF;
     if (old_fd == new_fd)
         return new_fd;
-    if (new_fd < 0 || new_fd >= m_max_open_file_descriptors)
+    if (new_fd < 0 || static_cast<size_t>(new_fd) >= fds().max_open())
         return EINVAL;
     m_fds[new_fd].set(*description);
     return new_fd;
diff --git a/Kernel/Syscalls/execve.cpp b/Kernel/Syscalls/execve.cpp
index 7539a82b9d..adf31e7a7c 100644
--- a/Kernel/Syscalls/execve.cpp
+++ b/Kernel/Syscalls/execve.cpp
@@ -573,15 +573,14 @@ KResult Process::do_exec(NonnullRefPtr<FileDescription> main_program_description
 
     clear_futex_queues_on_exec();
 
-    for (size_t i = 0; i < m_fds.size(); ++i) {
-        auto& description_and_flags = m_fds[i];
-        if (description_and_flags.description() && description_and_flags.flags() & FD_CLOEXEC)
-            description_and_flags = {};
-    }
+    fds().change_each([&](auto& file_description_metadata) {
+        if (file_description_metadata.is_valid() && file_description_metadata.flags() & FD_CLOEXEC)
+            file_description_metadata = {};
+    });
 
     int main_program_fd = -1;
     if (interpreter_description) {
-        main_program_fd = alloc_fd();
+        main_program_fd = m_fds.allocate();
         VERIFY(main_program_fd >= 0);
         auto seek_result = main_program_description->seek(0, SEEK_SET);
         VERIFY(!seek_result.is_error());
diff --git a/Kernel/Syscalls/fcntl.cpp b/Kernel/Syscalls/fcntl.cpp
index 3f28418c54..7d182583a0 100644
--- a/Kernel/Syscalls/fcntl.cpp
+++ b/Kernel/Syscalls/fcntl.cpp
@@ -14,7 +14,7 @@ KResultOr<FlatPtr> Process::sys$fcntl(int fd, int cmd, u32 arg)
 {
     REQUIRE_PROMISE(stdio);
     dbgln_if(IO_DEBUG, "sys$fcntl: fd={}, cmd={}, arg={}", fd, cmd, arg);
-    auto description = file_description(fd);
+    auto description = fds().file_description(fd);
     if (!description)
         return EBADF;
     // NOTE: The FD flags are not shared between FileDescription objects.
@@ -24,7 +24,7 @@ KResultOr<FlatPtr> Process::sys$fcntl(int fd, int cmd, u32 arg)
         int arg_fd = (int)arg;
         if (arg_fd < 0)
             return EINVAL;
-        int new_fd = alloc_fd(arg_fd);
+        int new_fd = fds().allocate(arg_fd);
         if (new_fd < 0)
             return new_fd;
         m_fds[new_fd].set(*description);
diff --git a/Kernel/Syscalls/ftruncate.cpp b/Kernel/Syscalls/ftruncate.cpp
index 3497cb9bf8..21065b06f7 100644
--- a/Kernel/Syscalls/ftruncate.cpp
+++ b/Kernel/Syscalls/ftruncate.cpp
@@ -17,7 +17,7 @@ KResultOr<FlatPtr> Process::sys$ftruncate(int fd, Userspace<off_t*> userspace_le
         return EFAULT;
     if (length < 0)
         return EINVAL;
-    auto description = file_description(fd);
+    auto description = fds().file_description(fd);
     if (!description)
         return EBADF;
     if (!description->is_writable())
diff --git a/Kernel/Syscalls/get_dir_entries.cpp b/Kernel/Syscalls/get_dir_entries.cpp
index 6125d08efe..880d4f1ae4 100644
--- a/Kernel/Syscalls/get_dir_entries.cpp
+++ b/Kernel/Syscalls/get_dir_entries.cpp
@@ -14,7 +14,7 @@ KResultOr<FlatPtr> Process::sys$get_dir_entries(int fd, Userspace<void*> user_bu
     REQUIRE_PROMISE(stdio);
     if (user_size > NumericLimits<ssize_t>::max())
         return EINVAL;
-    auto description = file_description(fd);
+    auto description = fds().file_description(fd);
     if (!description)
         return EBADF;
     auto buffer = UserOrKernelBuffer::for_user_buffer(user_buffer, static_cast<size_t>(user_size));
diff --git a/Kernel/Syscalls/inode_watcher.cpp b/Kernel/Syscalls/inode_watcher.cpp
index 38a3b51e79..af765c560e 100644
--- a/Kernel/Syscalls/inode_watcher.cpp
+++ b/Kernel/Syscalls/inode_watcher.cpp
@@ -17,7 +17,7 @@ KResultOr<FlatPtr> Process::sys$create_inode_watcher(u32 flags)
 {
     REQUIRE_PROMISE(rpath);
 
-    int fd = alloc_fd();
+    int fd = m_fds.allocate();
     if (fd < 0)
         return fd;
 
@@ -48,7 +48,7 @@ KResultOr<FlatPtr> Process::sys$inode_watcher_add_watch(Userspace<const Syscall:
     if (!copy_from_user(&params, user_params))
         return EFAULT;
 
-    auto description = file_description(params.fd);
+    auto description = fds().file_description(params.fd);
     if (!description)
         return EBADF;
     if (!description->is_inode_watcher())
@@ -75,7 +75,7 @@ KResultOr<FlatPtr> Process::sys$inode_watcher_add_watch(Userspace<const Syscall:
 
 KResultOr<FlatPtr> Process::sys$inode_watcher_remove_watch(int fd, int wd)
 {
-    auto description = file_description(fd);
+    auto description = fds().file_description(fd);
     if (!description)
         return EBADF;
     if (!description->is_inode_watcher())
diff --git a/Kernel/Syscalls/ioctl.cpp b/Kernel/Syscalls/ioctl.cpp
index 8c2750b9f7..4c668904e2 100644
--- a/Kernel/Syscalls/ioctl.cpp
+++ b/Kernel/Syscalls/ioctl.cpp
@@ -12,7 +12,7 @@ namespace Kernel {
 
 KResultOr<FlatPtr> Process::sys$ioctl(int fd, unsigned request, FlatPtr arg)
 {
-    auto description = file_description(fd);
+    auto description = fds().file_description(fd);
     if (!description)
         return EBADF;
     if (request == FIONBIO) {
diff --git a/Kernel/Syscalls/lseek.cpp b/Kernel/Syscalls/lseek.cpp
index 80e5415c89..31d559dc31 100644
--- a/Kernel/Syscalls/lseek.cpp
+++ b/Kernel/Syscalls/lseek.cpp
@@ -12,7 +12,7 @@ namespace Kernel {
 KResultOr<FlatPtr> Process::sys$lseek(int fd, Userspace<off_t*> userspace_offset, int whence)
 {
     REQUIRE_PROMISE(stdio);
-    auto description = file_description(fd);
+    auto description = fds().file_description(fd);
     if (!description)
         return EBADF;
     off_t offset;
diff --git a/Kernel/Syscalls/mmap.cpp b/Kernel/Syscalls/mmap.cpp
index 79353249ae..f88bc4d51e 100644
--- a/Kernel/Syscalls/mmap.cpp
+++ b/Kernel/Syscalls/mmap.cpp
@@ -224,7 +224,7 @@ KResultOr<FlatPtr> Process::sys$mmap(Userspace<const Syscall::SC_mmap_params*> u
             return EINVAL;
         if (static_cast<size_t>(offset) & ~PAGE_MASK)
             return EINVAL;
-        auto description = file_description(fd);
+        auto description = fds().file_description(fd);
         if (!description)
             return EBADF;
         if (description->is_directory())
diff --git a/Kernel/Syscalls/mount.cpp b/Kernel/Syscalls/mount.cpp
index f42c1bb213..9364790119 100644
--- a/Kernel/Syscalls/mount.cpp
+++ b/Kernel/Syscalls/mount.cpp
@@ -36,7 +36,7 @@ KResultOr<FlatPtr> Process::sys$mount(Userspace<const Syscall::SC_mount_params*>
     if (fs_type.is_null())
         return EFAULT;
 
-    auto description = file_description(source_fd);
+    auto description = fds().file_description(source_fd);
     if (!description.is_null())
         dbgln("mount {}: source fd {} @ {}", fs_type, source_fd, target);
     else
diff --git a/Kernel/Syscalls/open.cpp b/Kernel/Syscalls/open.cpp
index 4df12ef4a7..5ab765653c 100644
--- a/Kernel/Syscalls/open.cpp
+++ b/Kernel/Syscalls/open.cpp
@@ -44,7 +44,7 @@ KResultOr<FlatPtr> Process::sys$open(Userspace<const Syscall::SC_open_params*> u
         return path.error();
 
     dbgln_if(IO_DEBUG, "sys$open(dirfd={}, path='{}', options={}, mode={})", dirfd, path.value()->view(), options, mode);
-    int fd = alloc_fd();
+    int fd = m_fds.allocate();
     if (fd < 0)
         return fd;
 
@@ -52,7 +52,7 @@ KResultOr<FlatPtr> Process::sys$open(Userspace<const Syscall::SC_open_params*> u
     if (dirfd == AT_FDCWD) {
         base = current_directory();
     } else {
-        auto base_description = file_description(dirfd);
+        auto base_description = fds().file_description(dirfd);
         if (!base_description)
             return EBADF;
         if (!base_description->is_directory())
@@ -78,7 +78,7 @@ KResultOr<FlatPtr> Process::sys$open(Userspace<const Syscall::SC_open_params*> u
 KResultOr<FlatPtr> Process::sys$close(int fd)
 {
     REQUIRE_PROMISE(stdio);
-    auto description = file_description(fd);
+    auto description = fds().file_description(fd);
     dbgln_if(IO_DEBUG, "sys$close({}) {}", fd, description.ptr());
     if (!description)
         return EBADF;
diff --git a/Kernel/Syscalls/pipe.cpp b/Kernel/Syscalls/pipe.cpp
index b289a3958a..ef70709339 100644
--- a/Kernel/Syscalls/pipe.cpp
+++ b/Kernel/Syscalls/pipe.cpp
@@ -13,7 +13,7 @@ namespace Kernel {
 KResultOr<FlatPtr> Process::sys$pipe(int pipefd[2], int flags)
 {
     REQUIRE_PROMISE(stdio);
-    if (number_of_open_file_descriptors() + 2 > max_open_file_descriptors())
+    if (fds().open_count() + 2 > fds().max_open())
         return EMFILE;
     // Reject flags other than O_CLOEXEC.
     if ((flags & O_CLOEXEC) != flags)
@@ -29,13 +29,13 @@ KResultOr<FlatPtr> Process::sys$pipe(int pipefd[2], int flags)
     if (open_writer_result.is_error())
         return open_writer_result.error();
 
-    int reader_fd = alloc_fd();
+    int reader_fd = m_fds.allocate();
     m_fds[reader_fd].set(open_reader_result.release_value(), fd_flags);
     m_fds[reader_fd].description()->set_readable(true);
     if (!copy_to_user(&pipefd[0], &reader_fd))
         return EFAULT;
 
-    int writer_fd = alloc_fd();
+    int writer_fd = m_fds.allocate();
     m_fds[writer_fd].set(open_writer_result.release_value(), fd_flags);
     m_fds[writer_fd].description()->set_writable(true);
     if (!copy_to_user(&pipefd[1], &writer_fd))
diff --git a/Kernel/Syscalls/read.cpp b/Kernel/Syscalls/read.cpp
index f37b3d9d32..58ead804c5 100644
--- a/Kernel/Syscalls/read.cpp
+++ b/Kernel/Syscalls/read.cpp
@@ -34,7 +34,7 @@ KResultOr<FlatPtr> Process::sys$readv(int fd, Userspace<const struct iovec*> iov
             return EINVAL;
     }
 
-    auto description = file_description(fd);
+    auto description = fds().file_description(fd);
     if (!description)
         return EBADF;
 
@@ -76,7 +76,7 @@ KResultOr<FlatPtr> Process::sys$read(int fd, Userspace<u8*> buffer, size_t size)
     if (size > NumericLimits<ssize_t>::max())
         return EINVAL;
     dbgln_if(IO_DEBUG, "sys$read({}, {}, {})", fd, buffer.ptr(), size);
-    auto description = file_description(fd);
+    auto description = fds().file_description(fd);
     if (!description)
         return EBADF;
     if (!description->is_readable())
diff --git a/Kernel/Syscalls/select.cpp b/Kernel/Syscalls/select.cpp
index 87b61a4721..04758cf94f 100644
--- a/Kernel/Syscalls/select.cpp
+++ b/Kernel/Syscalls/select.cpp
@@ -61,7 +61,7 @@ KResultOr<FlatPtr> Process::sys$select(Userspace<const Syscall::SC_select_params
         return EFAULT;
 
     Thread::SelectBlocker::FDVector fds_info;
-    Vector<int, FD_SETSIZE> fds;
+    Vector<int, FD_SETSIZE> selected_fds;
     for (int fd = 0; fd < params.nfds; fd++) {
         auto block_flags = BlockFlags::None;
         if (params.readfds && FD_ISSET(fd, &fds_read))
@@ -73,14 +73,14 @@ KResultOr<FlatPtr> Process::sys$select(Userspace<const Syscall::SC_select_params
         if (block_flags == BlockFlags::None)
             continue;
 
-        auto description = file_description(fd);
+        auto description = fds().file_description(fd);
         if (!description) {
             dbgln("sys$select: Bad fd number {}", fd);
             return EBADF;
         }
         if (!fds_info.try_append({ description.release_nonnull(), block_flags }))
             return ENOMEM;
-        if (!fds.try_append(fd))
+        if (!selected_fds.try_append(fd))
             return ENOMEM;
     }
 
@@ -105,15 +105,15 @@ KResultOr<FlatPtr> Process::sys$select(Userspace<const Syscall::SC_select_params
         if (fd_entry.unblocked_flags == BlockFlags::None)
             continue;
         if (params.readfds && has_flag(fd_entry.unblocked_flags, BlockFlags::Read)) {
-            FD_SET(fds[i], &fds_read);
+            FD_SET(selected_fds[i], &fds_read);
             marked_fd_count++;
         }
         if (params.writefds && has_flag(fd_entry.unblocked_flags, BlockFlags::Write)) {
-            FD_SET(fds[i], &fds_write);
+            FD_SET(selected_fds[i], &fds_write);
             marked_fd_count++;
         }
         if (params.exceptfds && has_flag(fd_entry.unblocked_flags, BlockFlags::Exception)) {
-            FD_SET(fds[i], &fds_except);
+            FD_SET(selected_fds[i], &fds_except);
             marked_fd_count++;
         }
     }
@@ -135,7 +135,7 @@ KResultOr<FlatPtr> Process::sys$poll(Userspace<const Syscall::SC_poll_params*> u
     if (!copy_from_user(&params, user_params))
         return EFAULT;
 
-    if (params.nfds >= m_max_open_file_descriptors)
+    if (params.nfds >= fds().max_open())
         return ENOBUFS;
 
     Thread::BlockTimeout timeout;
@@ -165,7 +165,7 @@ KResultOr<FlatPtr> Process::sys$poll(Userspace<const Syscall::SC_poll_params*> u
     Thread::SelectBlocker::FDVector fds_info;
     for (size_t i = 0; i < params.nfds; i++) {
         auto& pfd = fds_copy[i];
-        auto description = file_description(pfd.fd);
+        auto description = fds().file_description(pfd.fd);
         if (!description) {
             dbgln("sys$poll: Bad fd number {}", pfd.fd);
             return EBADF;
diff --git a/Kernel/Syscalls/sendfd.cpp b/Kernel/Syscalls/sendfd.cpp
index f4f47e490d..0c82581a13 100644
--- a/Kernel/Syscalls/sendfd.cpp
+++ b/Kernel/Syscalls/sendfd.cpp
@@ -13,7 +13,7 @@ namespace Kernel {
 KResultOr<FlatPtr> Process::sys$sendfd(int sockfd, int fd)
 {
     REQUIRE_PROMISE(sendfd);
-    auto socket_description = file_description(sockfd);
+    auto socket_description = fds().file_description(sockfd);
     if (!socket_description)
         return EBADF;
     if (!socket_description->is_socket())
@@ -24,7 +24,7 @@ KResultOr<FlatPtr> Process::sys$sendfd(int sockfd, int fd)
     if (!socket.is_connected())
         return ENOTCONN;
 
-    auto passing_descriptor = file_description(fd);
+    auto passing_descriptor = fds().file_description(fd);
     if (!passing_descriptor)
         return EBADF;
 
@@ -35,7 +35,7 @@ KResultOr<FlatPtr> Process::sys$sendfd(int sockfd, int fd)
 KResultOr<FlatPtr> Process::sys$recvfd(int sockfd, int options)
 {
     REQUIRE_PROMISE(recvfd);
-    auto socket_description = file_description(sockfd);
+    auto socket_description = fds().file_description(sockfd);
     if (!socket_description)
         return EBADF;
     if (!socket_description->is_socket())
@@ -44,7 +44,7 @@ KResultOr<FlatPtr> Process::sys$recvfd(int sockfd, int options)
     if (!socket.is_local())
         return EAFNOSUPPORT;
 
-    int new_fd = alloc_fd();
+    int new_fd = m_fds.allocate();
     if (new_fd < 0)
         return new_fd;
 
diff --git a/Kernel/Syscalls/socket.cpp b/Kernel/Syscalls/socket.cpp
index b18906e413..108e3967f1 100644
--- a/Kernel/Syscalls/socket.cpp
+++ b/Kernel/Syscalls/socket.cpp
@@ -38,7 +38,7 @@ KResultOr<FlatPtr> Process::sys$socket(int domain, int type, int protocol)
 
     if ((type & SOCK_TYPE_MASK) == SOCK_RAW && !is_superuser())
         return EACCES;
-    int fd = alloc_fd();
+    int fd = m_fds.allocate();
     if (fd < 0)
         return fd;
     auto result = Socket::create(domain, type, protocol);
@@ -53,7 +53,7 @@ KResultOr<FlatPtr> Process::sys$socket(int domain, int type, int protocol)
 
 KResultOr<FlatPtr> Process::sys$bind(int sockfd, Userspace<const sockaddr*> address, socklen_t address_length)
 {
-    auto description = file_description(sockfd);
+    auto description = fds().file_description(sockfd);
     if (!description)
         return EBADF;
     if (!description->is_socket())
@@ -67,7 +67,7 @@ KResultOr<FlatPtr> Process::sys$listen(int sockfd, int backlog)
 {
     if (backlog < 0)
         return EINVAL;
-    auto description = file_description(sockfd);
+    auto description = fds().file_description(sockfd);
     if (!description)
         return EBADF;
     if (!description->is_socket())
@@ -96,10 +96,10 @@ KResultOr<FlatPtr> Process::sys$accept4(Userspace<const Syscall::SC_accept4_para
     if (user_address && !copy_from_user(&address_size, static_ptr_cast<const socklen_t*>(user_address_size)))
         return EFAULT;
 
-    int accepted_socket_fd = alloc_fd();
+    int accepted_socket_fd = m_fds.allocate();
     if (accepted_socket_fd < 0)
         return accepted_socket_fd;
-    auto accepting_socket_description = file_description(accepting_socket_fd);
+    auto accepting_socket_description = fds().file_description(accepting_socket_fd);
     if (!accepting_socket_description)
         return EBADF;
     if (!accepting_socket_description->is_socket())
@@ -148,10 +148,10 @@ KResultOr<FlatPtr> Process::sys$accept4(Userspace<const Syscall::SC_accept4_para
 
 KResultOr<FlatPtr> Process::sys$connect(int sockfd, Userspace<const sockaddr*> user_address, socklen_t user_address_size)
 {
-    int fd = alloc_fd();
+    int fd = m_fds.allocate();
     if (fd < 0)
         return fd;
-    auto description = file_description(sockfd);
+    auto description = fds().file_description(sockfd);
     if (!description)
         return EBADF;
     if (!description->is_socket())
@@ -168,7 +168,7 @@ KResultOr<FlatPtr> Process::sys$shutdown(int sockfd, int how)
     REQUIRE_PROMISE(stdio);
     if (how & ~SHUT_RDWR)
         return EINVAL;
-    auto description = file_description(sockfd);
+    auto description = fds().file_description(sockfd);
     if (!description)
         return EBADF;
     if (!description->is_socket())
@@ -199,7 +199,7 @@ KResultOr<FlatPtr> Process::sys$sendmsg(int sockfd, Userspace<const struct msghd
     Userspace<const sockaddr*> user_addr((FlatPtr)msg.msg_name);
     socklen_t addr_length = msg.msg_namelen;
 
-    auto description = file_description(sockfd);
+    auto description = fds().file_description(sockfd);
     if (!description)
         return EBADF;
     if (!description->is_socket())
@@ -236,7 +236,7 @@ KResultOr<FlatPtr> Process::sys$recvmsg(int sockfd, Userspace<struct msghdr*> us
     Userspace<sockaddr*> user_addr((FlatPtr)msg.msg_name);
     Userspace<socklen_t*> user_addr_length(msg.msg_name ? (FlatPtr)&user_msg.unsafe_userspace_ptr()->msg_namelen : 0);
 
-    auto description = file_description(sockfd);
+    auto description = fds().file_description(sockfd);
     if (!description)
         return EBADF;
     if (!description->is_socket())
@@ -301,7 +301,7 @@ int Process::get_sock_or_peer_name(const Params& params)
     if (addrlen_value <= 0)
         return EINVAL;
 
-    auto description = file_description(params.sockfd);
+    auto description = fds().file_description(params.sockfd);
     if (!description)
         return EBADF;
 
@@ -356,7 +356,7 @@ KResultOr<FlatPtr> Process::sys$getsockopt(Userspace<const Syscall::SC_getsockop
     if (!copy_from_user(&value_size, params.value_size, sizeof(socklen_t)))
         return EFAULT;
 
-    auto description = file_description(sockfd);
+    auto description = fds().file_description(sockfd);
     if (!description)
         return EBADF;
     if (!description->is_socket())
@@ -373,7 +373,7 @@ KResultOr<FlatPtr> Process::sys$setsockopt(Userspace<const Syscall::SC_setsockop
     if (!copy_from_user(&params, user_params))
         return EFAULT;
     Userspace<const void*> user_value((FlatPtr)params.value);
-    auto description = file_description(params.sockfd);
+    auto description = fds().file_description(params.sockfd);
     if (!description)
         return EBADF;
     if (!description->is_socket())
@@ -401,12 +401,12 @@ KResultOr<FlatPtr> Process::sys$socketpair(Userspace<const Syscall::SC_socketpai
     auto pair = result.value();
 
     int fds[2];
-    fds[0] = alloc_fd();
+    fds[0] = m_fds.allocate();
     if (fds[0] < 0)
         return ENFILE;
     setup_socket_fd(fds[0], pair.description1, params.type);
 
-    fds[1] = alloc_fd();
+    fds[1] = m_fds.allocate();
     if (fds[1] < 0) {
         // FIXME: This leaks fds[0]
         return ENFILE;
diff --git a/Kernel/Syscalls/stat.cpp b/Kernel/Syscalls/stat.cpp
index 60b7ddff3a..409b1b92eb 100644
--- a/Kernel/Syscalls/stat.cpp
+++ b/Kernel/Syscalls/stat.cpp
@@ -15,7 +15,7 @@ namespace Kernel {
 KResultOr<FlatPtr> Process::sys$fstat(int fd, Userspace<stat*> user_statbuf)
 {
     REQUIRE_PROMISE(stdio);
-    auto description = file_description(fd);
+    auto description = fds().file_description(fd);
     if (!description)
         return EBADF;
     stat buffer = {};
@@ -38,7 +38,7 @@ KResultOr<FlatPtr> Process::sys$stat(Userspace<const Syscall::SC_stat_params*> u
     if (params.dirfd == AT_FDCWD) {
         base = current_directory();
     } else {
-        auto base_description = file_description(params.dirfd);
+        auto base_description = fds().file_description(params.dirfd);
         if (!base_description)
             return EBADF;
         if (!base_description->is_directory())
diff --git a/Kernel/Syscalls/statvfs.cpp b/Kernel/Syscalls/statvfs.cpp
index 0e6562a7be..6d34369765 100644
--- a/Kernel/Syscalls/statvfs.cpp
+++ b/Kernel/Syscalls/statvfs.cpp
@@ -87,7 +87,7 @@ KResultOr<FlatPtr> Process::sys$fstatvfs(int fd, statvfs* buf)
 {
     REQUIRE_PROMISE(stdio);
 
-    auto description = file_description(fd);
+    auto description = fds().file_description(fd);
     if (!description)
         return EBADF;
 
diff --git a/Kernel/Syscalls/sysconf.cpp b/Kernel/Syscalls/sysconf.cpp
index 9460b7c585..2a6dae7b52 100644
--- a/Kernel/Syscalls/sysconf.cpp
+++ b/Kernel/Syscalls/sysconf.cpp
@@ -18,7 +18,7 @@ KResultOr<FlatPtr> Process::sys$sysconf(int name)
     case _SC_NPROCESSORS_ONLN:
         return Processor::processor_count();
     case _SC_OPEN_MAX:
-        return max_open_file_descriptors();
+        return fds().max_open();
     case _SC_PAGESIZE:
         return PAGE_SIZE;
     case _SC_TTY_NAME_MAX:
diff --git a/Kernel/Syscalls/ttyname.cpp b/Kernel/Syscalls/ttyname.cpp
index c544b52a13..01f8776b93 100644
--- a/Kernel/Syscalls/ttyname.cpp
+++ b/Kernel/Syscalls/ttyname.cpp
@@ -14,7 +14,7 @@ namespace Kernel {
 KResultOr<FlatPtr> Process::sys$ttyname(int fd, Userspace<char*> buffer, size_t size)
 {
     REQUIRE_PROMISE(tty);
-    auto description = file_description(fd);
+    auto description = fds().file_description(fd);
     if (!description)
         return EBADF;
     if (!description->is_tty())
@@ -30,7 +30,7 @@ KResultOr<FlatPtr> Process::sys$ttyname(int fd, Userspace<char*> buffer, size_t
 KResultOr<FlatPtr> Process::sys$ptsname(int fd, Userspace<char*> buffer, size_t size)
 {
     REQUIRE_PROMISE(tty);
-    auto description = file_description(fd);
+    auto description = fds().file_description(fd);
     if (!description)
         return EBADF;
     auto* master_pty = description->master_pty();
diff --git a/Kernel/Syscalls/write.cpp b/Kernel/Syscalls/write.cpp
index fece780d9c..2ede957a53 100644
--- a/Kernel/Syscalls/write.cpp
+++ b/Kernel/Syscalls/write.cpp
@@ -33,7 +33,7 @@ KResultOr<FlatPtr> Process::sys$writev(int fd, Userspace<const struct iovec*> io
             return EINVAL;
     }
 
-    auto description = file_description(fd);
+    auto description = fds().file_description(fd);
     if (!description)
         return EBADF;
 
@@ -105,7 +105,7 @@ KResultOr<FlatPtr> Process::sys$write(int fd, Userspace<const u8*> data, size_t
         return EINVAL;
 
     dbgln_if(IO_DEBUG, "sys$write({}, {}, {})", fd, data.ptr(), size);
-    auto description = file_description(fd);
+    auto description = fds().file_description(fd);
     if (!description)
         return EBADF;
     if (!description->is_writable())