oops

5f3d853d · Robert Morris · 7e8cd598 · 5f3d853d
--- a/namecache.c
+++ b/namecache.c
+//
+// file-system name cache
+//
+// to do:
+//   use ns.c namespaces
+//   invalidation (for rename, unlink)
+//   does directory inum need to be locked?
+//   need a lock to make table lookup and iget atomic?
+//   insert when file created, not just looked up
+//
+
+#include "types.h"
+#include "defs.h"
+#include "param.h"
+#include "stat.h"
+#include "mmu.h"
+#include "spinlock.h"
+#include "condvar.h"
+#include "queue.h"
+#include "proc.h"
+#include "buf.h"
+#include "fs.h"
+#include "file.h"
+
+struct spinlock nc_lock;
+
+// map the tuple <dev,dinum,name> to cinum;
+struct nce {
+  int valid;
+  uint dev;
+  uint dinum; // directory inumber
+  char name[DIRSIZ];
+  uint cinum; // child inumber
+};
+#define NCE 32
+struct nce nce[NCE];
+
+void
+nc_init()
+{
+  initlock(&nc_lock, "namecache");
+}
+
+// nc_lock must be held
+struct nce *
+nc_lookup1(struct inode *dir, char *name)
+{
+  for(int i = 0; i < NCE; i++){
+    struct nce *e = &nce[i];
+    if(e->valid && e->dev == dir->dev && e->dinum == dir->inum &&
+       namecmp(name, e->name) == 0){
+      return e;
+    }
+  }
+  return 0;
+}
+
+struct inode *
+nc_lookup(struct inode *dir, char *name)
+{
+  uint inum = 0;
+
+  acquire(&nc_lock);
+  struct nce *e = nc_lookup1(dir, name);
+  if(e)
+    inum = e->cinum;
+  release(&nc_lock);
+
+  if(inum)
+    return iget(dir->dev, inum);
+  else
+    return 0;
+}
+
+void
+nc_insert(struct inode *dir, char *name, struct inode *ip)
+{
+  acquire(&nc_lock);
+
+  struct nce *e = nc_lookup1(dir, name);
+  if(e){
+    if(e->cinum != ip->inum)
+      panic("nc_insert change");
+    release(&nc_lock);
+    return;
+  }
+
+  for(int i = 0; i < NCE; i++){
+    e = &nce[i];
+    if(e->valid == 0){
+      e->valid = 1;
+      e->dev = dir->dev;
+      e->dinum = dir->inum;
+      strncpy(e->name, name, DIRSIZ);
+      e->cinum = ip->inum;
+      break;
+    }
+  }
+
+  release(&nc_lock);
+}
+
+void
+nc_invalidate(struct inode *dir, char *name)
+{
+  acquire(&nc_lock);
+  struct nce *e = nc_lookup1(dir, name);
+  if(e)
+    e->valid = 0;
+  release(&nc_lock);
+}