Some reference counting code to help ref. count files

33750412 · Silas Boyd-Wickizer · cac83063 · 33750412 · 33750412 · 33750412
--- a/include/file.hh
+++ b/include/file.hh
@@ -4,13 +4,15 @@
 #include "ns.hh"
 #include "gc.hh"
 #include "atomic.hh"
+#include "ref.hh"
 u64 namehash(const strbuf<DIRSIZ>&);
-struct file {
+struct file : public referenced {
  file() : type(file::FD_NONE), readable(0), writable(0), 
-           socket(0), pipe(nullptr), ip(nullptr), off(0), 
+           socket(0), pipe(nullptr), ip(nullptr), off(0) {
-           ref_(1) {}
+    inc();
+  }
  file *dup();
  void close();
@@ -25,8 +27,8 @@ struct file {
  u32 off;
  NEW_DELETE_OPS(file);
-private:
+protected:
-  std::atomic<int> ref_;
+  virtual void onzero() const;
 };
 // in-core file system types

--- a/include/filetable.hh
+++ b/include/filetable.hh
@@ -28,16 +28,20 @@ public:
    destroylock(&lock_);
  }
-  file *getfile(int fd) {
+  bool getfile(int fd, sref<file> *sf) {
    file *f;
    if (fd < 0 || fd >= NOFILE)
-      return nullptr;
+      return false;
    acquire(&lock_);
    f = ofile_[fd];
-    // XXX(sbw) f->inc();
+    if (!f) {
+      release(&lock_);
+      return false;
+    }
+    sf->init(f);
    release(&lock_);
-    return f;
+    return true;
  }
  int allocfd(struct file *f) {

--- a/include/ref.hh
+++ b/include/ref.hh
+#include "atomic.hh"
+template <class T>
+class sref {
+public:
+  sref(T* p = nullptr) : ptr_(p) {
+    if (ptr_)
+      ptr_->inc();
+  }
+  ~sref() {
+    if (ptr_)
+      ptr_->dec();
+  }
+  void init(T* p) {
+    const T* save = ptr_;
+    ptr_ = p;
+    if (ptr_)
+      ptr_->inc();
+    if (save)
+      save->dec();
+  }
+  bool operator==(const sref<T>& pr) const { return ptr_ == pr.ptr_; }
+  bool operator!=(const sref<T>& pr) const { return ptr_ != pr.ptr_; }
+  bool operator==(T* p) const { return ptr_ == p; }
+  bool operator!=(T* p) const { return ptr_ != p; }
+  const T * operator->() const { return ptr_; }
+  T * operator->() { return ptr_; }
+  T * ptr() const { return ptr_; }
+private:
+  sref<T>& operator=(sref<T>& mp);
+  sref<T>& operator=(T* p);
+  sref<T>& operator=(const sref<T>& pr);
+  sref(const sref<T>& pr);
+  T *ptr_;
+};
+template <class T>
+class lref {
+public:
+  lref(T* p = nullptr) : ptr_(p) {
+    if (ptr_)
+      ptr_->inc();
+  }
+  lref(const lref<T>& pr) : ptr_(pr.ptr_) {
+    if (ptr_)
+      ptr_->inc();
+  }
+  ~lref() {
+    if (ptr_)
+      ptr_->dec();
+  }
+  bool operator==(const lref<T>& pr) const { return ptr_ == pr.ptr_; }
+  bool operator!=(const lref<T>& pr) const { return ptr_ != pr.ptr_; }
+  bool operator==(T* p) const { return ptr_ == p; }
+  bool operator!=(T* p) const { return ptr_ != p; }
+  const T * operator->() const { return ptr_; }
+  T * operator->() { return ptr_; }
+  T * ptr() const { return ptr_; }
+  lref<T>& operator=(const lref<T>& pr) {
+    const T* save = ptr_;
+    ptr_ = pr.ptr_; 
+    if (ptr_)
+      ptr_->inc();
+    if (save)
+      save->dec();
+    return *this;
+  }
+private:
+  lref<T>& operator=( lref<T>& mp );
+  lref<T>& operator=( T* p );
+  T *ptr_;
+};
+class referenced {
+public:
+  referenced() : ref_(0) {}
+  u64 ref() const { 
+    return ref_;
+  }
+  inline const referenced* inc() const { 
+    ++ref_;
+    return this;
+  }
+  inline void dec() const {
+    if (--ref_ == 0)
+      onzero();
+  }
+  NEW_DELETE_OPS(referenced);
+protected:
+  virtual ~referenced() { }
+  virtual void onzero() const { delete this; }
+private:
+    mutable std::atomic<u64> ref_;
+};
--- a/kernel/async.cc
+++ b/kernel/async.cc
@@ -56,7 +56,7 @@ long
 sys_async(int fd, size_t count, off_t off,
          msgid_t msgid, pageid_t pageid)
 {
-  struct file *f;
+  sref<file> f;;
  cwork *w;
  char *kshared = myproc()->vmap->kshared;
@@ -72,7 +72,7 @@ sys_async(int fd, size_t count, off_t off,
  msg = &ipcctl->msg[msgid];
  ubuf = (kshared+PGSIZE+(pageid*PGSIZE));
-  if ((f = myproc()->ftable->getfile(fd)) == nullptr)
+  if (!myproc()->ftable->getfile(fd, &f))
    return -1;
  if (f->type != file::FD_INODE)
    return -1;

--- a/kernel/file.cc
+++ b/kernel/file.cc
@@ -10,11 +10,8 @@
 struct devsw __mpalign__ devsw[NDEV];
 void
-file::close(void)
+file::onzero() const
 {
-  if (--ref_ > 0)
-    return;
  if(type == file::FD_PIPE)
    pipeclose(pipe, writable);
  else if(type == file::FD_INODE)
@@ -26,11 +23,16 @@ file::close(void)
  delete this;
 }
+void
+file::close(void)
+{
+  dec();
+}
 file*
 file::dup(void)
 {
-  if (ref_++ < 1)
+  inc();
-    panic("file::dup");
  return this;
 }

--- a/kernel/sysfile.cc
+++ b/kernel/sysfile.cc
@@ -12,24 +12,16 @@
 #include "cpu.hh"
 #include "net.hh"
-// Fetch the nth word-sized system call argument as a file descriptor
+static bool
-// and return both the descriptor and the corresponding struct file.
+getfile(int fd, sref<file> *f)
-static int
-argfd(int fd, struct file **pf)
 {
-  struct file *f;
+  return myproc()->ftable->getfile(fd, f);
-  if((f = myproc()->ftable->getfile(fd)) == nullptr)
-    return -1;
-  if(pf)
-    *pf = f;
-  return 0;
 }
 // Allocate a file descriptor for the given file.
 // Takes over file reference from caller on success.
 static int
-fdalloc(struct file *f)
+fdalloc(file *f)
 {
  return myproc()->ftable->allocfd(f);
 }
@@ -37,35 +29,37 @@ fdalloc(struct file *f)
 long
 sys_dup(int ofd)
 {
-  struct file *f;
+  sref<file> f;
  int fd;
-  if(argfd(ofd, &f) < 0)
+  if (!getfile(ofd, &f))
    return -1;
-  if((fd=fdalloc(f)) < 0)
+  f->inc();
+  if ((fd = fdalloc(f.ptr())) < 0) {
+    f->dec();
    return -1;
-  f->dup();
+  }
  return fd;
 }
 s64
 sys_read(int fd, char *p, int n)
 {
-  struct file *f;
+  sref<file> f;
-  if(argfd(fd, &f) < 0 || argcheckptr(p, n) < 0)
+  if(!getfile(fd, &f) || argcheckptr(p, n) < 0)
    return -1;
-  return fileread(f, p, n);
+  return fileread(f.ptr(), p, n);
 }
 ssize_t
 sys_pread(int fd, void *ubuf, size_t count, off_t offset)
 {
-  struct file *f;
+  sref<file> f;
  uptr i = (uptr)ubuf;
  int r;
-  if ((f = myproc()->ftable->getfile(fd)) == nullptr)
+  if (!getfile(fd, &f))
    return -1;
  for(uptr va = PGROUNDDOWN(i); va < i+count; va = va + PGSIZE)
@@ -86,19 +80,19 @@ sys_pread(int fd, void *ubuf, size_t count, off_t offset)
 long
 sys_write(int fd, char *p, int n)
 {
-  struct file *f;
+  sref<file> f;
-  if(argfd(fd, &f) < 0 || argcheckptr(p, n) < 0)
+  if (!getfile(fd, &f) || argcheckptr(p, n) < 0)
    return -1;
-  return filewrite(f, p, n);
+  return filewrite(f.ptr(), p, n);
 }
 long
 sys_close(int fd)
 {
-  struct file *f;
+  sref<file> f;
-  if(argfd(fd, &f) < 0)
+  if (!getfile(fd, &f))
    return -1;
  myproc()->ftable->close(fd);
  return 0;
@@ -107,11 +101,11 @@ sys_close(int fd)
 long
 sys_fstat(int fd, struct stat *st)
 {
-  struct file *f;
+  sref<file> f;
-  if(argfd(fd, &f) < 0 || argcheckptr(st, sizeof(*st)) < 0)
+  if (!getfile(fd, &f) || argcheckptr(st, sizeof(*st)) < 0)
    return -1;
-  return filestat(f, st);
+  return filestat(f.ptr(), st);
 }
 // Create the path new as a link to the same inode as old.
@@ -287,8 +281,8 @@ sys_openat(int dirfd, const char *path, int omode)
  } else if (dirfd < 0 || dirfd >= NOFILE) {
    return -1;
  } else {
-    struct file *fdir = myproc()->ftable->getfile(dirfd);
+    sref<file> fdir;
-    if (fdir == nullptr || fdir->type != file::FD_INODE)
+    if (!getfile(dirfd, &fdir) || fdir->type != file::FD_INODE)
      return -1;
    cwd = fdir->ip;
  }
@@ -430,17 +424,16 @@ freesocket(int fd)
  myproc()->ftable->close(fd);
 }
-static int
+static bool
-getsocket(int fd, struct file **ret)
+getsocket(int fd, sref<file> *f)
 {
-  struct file *f;
+  if (!getfile(fd, f))
-  if ((f = myproc()->ftable->getfile(fd)) == nullptr)
+    return false;
-    return -1;
+  if ((*f)->type != file::FD_SOCKET) {
-  if (f->type != file::FD_SOCKET)
+    f->init(nullptr);
-    return -1;
+    return false;
+  }
-  *ret = f;
+  return true;
-  return 0;
 }
 static int
@@ -494,9 +487,9 @@ long
 sys_bind(int xsock, void *xaddr, int xaddrlen)
 {
  extern long netbind(int, void*, int);
-  struct file *f;
+  sref<file> f;
-  if (getsocket(xsock, &f))
+  if (!getsocket(xsock, &f))
    return -1;
  return netbind(f->socket, xaddr, xaddrlen);
@@ -506,9 +499,9 @@ long
 sys_listen(int xsock, int backlog)
 {
  extern long netlisten(int, int);
-  struct file *f;
+  sref<file> f;
-  if (getsocket(xsock, &f))
+  if (!getsocket(xsock, &f))
    return -1;
  return netlisten(f->socket, backlog);
@@ -518,11 +511,12 @@ long
 sys_accept(int xsock, void *xaddr, void *xaddrlen)
 {
  extern long netaccept(int, void*, void*);
-  struct file *f, *cf;
+  file *cf;
+  sref<file> f;
  int cfd;
  int ss;
-  if (getsocket(xsock, &f))
+  if (!getsocket(xsock, &f))
    return -1;
  if (allocsocket(&cf, &cfd))