protect ip->valid and ip->nlink with sleep lock in iput()

70d912b3 · Robert Morris · 3375df50 · 70d912b3 · 70d912b3
--- a/file.h
+++ b/file.h
@@ -14,8 +14,8 @@ struct inode {
  uint dev;           // Device number
  uint inum;          // Inode number
  int ref;            // Reference count
-  struct sleeplock lock;
-  int valid;          // remainder has been read from disk?
+  struct sleeplock lock; // protects everything below here
+  int valid;          // inode has been read from disk?

  short type;         // copy of disk inode
  short major;

--- a/fs.c
+++ b/fs.c
@@ -320,15 +320,17 @@ void
 iput(struct inode *ip)
 {
  acquire(&icache.lock);
-  if(ip->ref == 1 && ip->valid && ip->nlink == 0){
-    // inode has no links and no other references: truncate and free.
+  if(ip->ref == 1){
    acquiresleep(&ip->lock);
-    release(&icache.lock);
-    itrunc(ip);
-    ip->type = 0;
-    iupdate(ip);
-    acquire(&icache.lock);
-    ip->valid = 0;
+    if(ip->valid && ip->nlink == 0){
+      // inode has no links and no other references: truncate and free.
+      release(&icache.lock);
+      itrunc(ip);
+      ip->type = 0;
+      iupdate(ip);
+      ip->valid = 0;
+      acquire(&icache.lock);
+    }
    releasesleep(&ip->lock);
  }
  ip->ref--;