From 5053dd6a6d2b481bfcddbd91bacc885b9f0e0ff5 Mon Sep 17 00:00:00 2001
From: Robert Morris <rtm@csail.mit.edu>
Date: Mon, 15 Aug 2011 12:44:20 -0400
Subject: avoid deadlock by calling begin_trans() before locking any inodes

---
 sysfile.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

(limited to 'sysfile.c')

diff --git a/sysfile.c b/sysfile.c
index ca54013..c9d3594 100644
--- a/sysfile.c
+++ b/sysfile.c
@@ -116,14 +116,16 @@ sys_link(void)
     return -1;
   if((ip = namei(old)) == 0)
     return -1;
+
+  begin_trans();
+
   ilock(ip);
   if(ip->type == T_DIR){
     iunlockput(ip);
+    commit_trans();
     return -1;
   }
 
-  begin_trans();
-
   ip->nlink++;
   iupdate(ip);
   iunlock(ip);
@@ -180,16 +182,21 @@ sys_unlink(void)
     return -1;
   if((dp = nameiparent(path, name)) == 0)
     return -1;
+
+  begin_trans();
+
   ilock(dp);
 
   // Cannot unlink "." or "..".
   if(namecmp(name, ".") == 0 || namecmp(name, "..") == 0){
     iunlockput(dp);
+    commit_trans();
     return -1;
   }
 
   if((ip = dirlookup(dp, name, &off)) == 0){
     iunlockput(dp);
+    commit_trans();
     return -1;
   }
   ilock(ip);
@@ -199,11 +206,10 @@ sys_unlink(void)
   if(ip->type == T_DIR && !isdirempty(ip)){
     iunlockput(ip);
     iunlockput(dp);
+    commit_trans();
     return -1;
   }
 
-  begin_trans();
-
   memset(&de, 0, sizeof(de));
   if(writei(dp, (char*)&de, off, sizeof(de)) != sizeof(de))
     panic("unlink: writei");
-- 
cgit v1.2.3