Ensure vmnodes increment the inode ref (before decrementing it)

28ead2d3 · Silas Boyd-Wickizer · 87263b9c · 28ead2d3 · 28ead2d3 · 28ead2d3
--- a/include/vm.hh
+++ b/include/vm.hh
@@ -22,7 +22,6 @@ struct vmnode {
  atomic<bool> empty;
  atomic<char*> page[128];
  const enum vmntype type;
-  struct inode *const ip;
  const u64 offset;
  const u64 sz;

@@ -42,6 +41,7 @@ struct vmnode {
  NEW_DELETE_OPS(vmnode);
 private:
  atomic<u64> ref_;
+  struct inode *const ip;
 };

 // A mapping of a chunk of an address space to

--- a/kernel/exec.cc
+++ b/kernel/exec.cc
@@ -159,6 +159,9 @@ exec(const char *path, char **argv, void *ascopev)

  if((ip = namei(myproc()->cwd, path)) == 0)
    return -1;
+  auto cleanup = scoped_cleanup([&ip](){
+    iput(ip);
+  });

  if(myproc()->worker != nullptr)
    return -1;

--- a/kernel/vm.cc
+++ b/kernel/vm.cc
@@ -27,8 +27,11 @@ enum { tlb_lazy = 1 };

 vmnode::vmnode(u64 npg, vmntype ntype, inode *i, u64 off, u64 s)
  : npages(npg), empty(true), type(ntype),
-    ip(i), offset(off), sz(s), ref_(0)
+    offset(off), sz(s), ref_(0), ip(i)
 {
+  if (ip != nullptr)
+    ip->inc();
+
  if (npg > NELEM(page))
    panic("vmnode too big\n");
  // XXX Maybe vmnode should take just a byte size
@@ -46,7 +49,7 @@ vmnode::~vmnode()
  for(u64 i = 0; i < npages; i++)
    if (page[i])
      kfree(page[i]);
-  if (ip)
+  if (ip != nullptr)
    iput(ip);
 }