Only ilock in pwrite is there's a chance of growing the file

f752e22a · Silas Boyd-Wickizer · 08d9fdca · f752e22a
--- a/kernel/file.cc
+++ b/kernel/file.cc
@@ -126,12 +126,23 @@ ssize_t
 file::pwrite(const char *addr, size_t n, off_t off)
 {
  if(type == file::FD_INODE){
+    bool unlock;
    int r;
-    ilock(ip, 1);
    if(ip->type == 0 || ip->type == T_DIR)
      panic("filewrite but 0 or T_DIR");
+    unlock = false;
+    if (n+off > ip->size) {
+      ilock(ip, 1);
+      unlock = true;
+    }
    r = writei(ip, addr, off, n);
-    iunlock(ip);
+    if (unlock)
+      iunlock(ip);
    return r;
  }
  return -1;