retry on concurrent create

0783a25b · Nickolai Zeldovich · 0b4a7695 · 0783a25b
--- a/sysfile.c
+++ b/sysfile.c
@@ -227,6 +227,7 @@ create(char *path, short type, short major, short minor)
  struct inode *ip, *dp;
  char name[DIRSIZ];

+ retry:
  if((dp = nameiparent(path, name)) == 0)
    return 0;
  if(dp->type != T_DIR)
@@ -257,8 +258,13 @@ create(char *path, short type, short major, short minor)
      panic("create dots");
  }

-  if(dirlink(dp, name, ip->inum) < 0)
-    panic("create: dirlink");
+  if(dirlink(dp, name, ip->inum) < 0) {
+    // create race
+    ip->nlink--;
+    iunlockput(ip);
+    iput(dp);
+    goto retry;
+  }

  //nc_insert(dp, name, ip);
  iput(dp);