From 13387c083807aff01265433991ac3c1af194c6c1 Mon Sep 17 00:00:00 2001
From: Nick Craig-Wood <nick@craig-wood.com>
Date: Mon, 3 Dec 2018 21:51:39 +0000
Subject: [PATCH] vfs: fix deadlock on concurrent operations on a directory -
 fixes #2811

Before this fix there were two paths where concurrent use of a
directory could take the file lock then directory lock and the other
would take the locks in the reverse order.

Fix this by narrowing the locking windows so the file lock and
directory lock don't overlap.
---
 vfs/file.go | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/vfs/file.go b/vfs/file.go
index 966e0f4f1..8e9f91ecc 100644
--- a/vfs/file.go
+++ b/vfs/file.go
@@ -331,9 +331,10 @@ func (f *File) setSize(n int64) {
 // Update the object when written and add it to the directory
 func (f *File) setObject(o fs.Object) {
 	f.mu.Lock()
-	defer f.mu.Unlock()
 	f.o = o
 	_ = f.applyPendingModTime()
+	f.mu.Unlock()
+
 	f.d.addObject(f)
 }
 
@@ -440,20 +441,23 @@ func (f *File) Sync() error {
 
 // Remove the file
 func (f *File) Remove() error {
-	f.mu.Lock()
-	defer f.mu.Unlock()
-	f.muRW.Lock()
-	defer f.muRW.Unlock()
 	if f.d.vfs.Opt.ReadOnly {
 		return EROFS
 	}
+	f.mu.Lock()
+	f.muRW.Lock()
 	if f.o != nil {
 		err := f.o.Remove()
 		if err != nil {
 			fs.Errorf(f, "File.Remove file error: %v", err)
+			f.muRW.Unlock()
+			f.mu.Unlock()
 			return err
 		}
 	}
+	f.muRW.Unlock()
+	f.mu.Unlock()
+
 	// Remove the item from the directory listing
 	f.d.delObject(f.Name())
 	// Remove the object from the cache