From aea8776a4368ee8ab02b436717d219d0e868d701 Mon Sep 17 00:00:00 2001
From: Nick Craig-Wood <nick@craig-wood.com>
Date: Fri, 12 Mar 2021 16:15:28 +0000
Subject: [PATCH] vfs: fix modtimes not updating when writing via cache - fixes
 #4763

This reads modtime from a dirty cache item if it exists. This mirrors
the way reading the size works.

This fixes the mod time not updating when the file is written, only
when the writeback completes.

See: https://forum.rclone.org/t/rclone-mount-and-changing-timestamps-after-writes/22629
---
 vfs/file.go           | 11 +++++++++++
 vfs/vfscache/cache.go |  3 ++-
 vfs/vfscache/item.go  | 31 ++++++++++++++++++++++++-------
 3 files changed, 37 insertions(+), 8 deletions(-)

diff --git a/vfs/file.go b/vfs/file.go
index f06b35bb1..535aa414f 100644
--- a/vfs/file.go
+++ b/vfs/file.go
@@ -300,6 +300,17 @@ func (f *File) ModTime() (modTime time.Time) {
 	if d.vfs.Opt.NoModTime {
 		return d.ModTime()
 	}
+	// Read the modtime from a dirty item if it exists
+	if f.d.vfs.Opt.CacheMode >= vfscommon.CacheModeMinimal {
+		if item := f.d.vfs.cache.DirtyItem(f._path()); item != nil {
+			modTime, err := item.GetModTime()
+			if err != nil {
+				fs.Errorf(f._path(), "ModTime: Item GetModTime failed: %v", err)
+			} else {
+				return modTime
+			}
+		}
+	}
 	if !pendingModTime.IsZero() {
 		return pendingModTime
 	}
diff --git a/vfs/vfscache/cache.go b/vfs/vfscache/cache.go
index 2d1950ab0..45fc98554 100644
--- a/vfs/vfscache/cache.go
+++ b/vfs/vfscache/cache.go
@@ -237,7 +237,8 @@ func (c *Cache) InUse(name string) bool {
 	return item.inUse()
 }
 
-// DirtyItem the Item if it exists in the cache and is Dirty
+// DirtyItem returns the Item if it exists in the cache **and** is
+// dirty otherwise it returns nil.
 //
 // name should be a remote path not an osPath
 func (c *Cache) DirtyItem(name string) (item *Item) {
diff --git a/vfs/vfscache/item.go b/vfs/vfscache/item.go
index 8fffb2bc5..b7f6f0700 100644
--- a/vfs/vfscache/item.go
+++ b/vfs/vfscache/item.go
@@ -359,17 +359,22 @@ func (item *Item) Truncate(size int64) (err error) {
 	return nil
 }
 
+// _stat gets the current stat of the backing file
+//
+// Call with mutex held
+func (item *Item) _stat() (fi os.FileInfo, err error) {
+	if item.fd != nil {
+		return item.fd.Stat()
+	}
+	osPath := item.c.toOSPath(item.name) // No locking in Cache
+	return os.Stat(osPath)
+}
+
 // _getSize gets the current size of the item and updates item.info.Size
 //
 // Call with mutex held
 func (item *Item) _getSize() (size int64, err error) {
-	var fi os.FileInfo
-	if item.fd != nil {
-		fi, err = item.fd.Stat()
-	} else {
-		osPath := item.c.toOSPath(item.name) // No locking in Cache
-		fi, err = os.Stat(osPath)
-	}
+	fi, err := item._stat()
 	if err != nil {
 		if os.IsNotExist(err) && item.o != nil {
 			size = item.o.Size()
@@ -1187,6 +1192,18 @@ func (item *Item) setModTime(modTime time.Time) {
 	item.mu.Unlock()
 }
 
+// GetModTime of the cache file
+func (item *Item) GetModTime() (modTime time.Time, err error) {
+	// defer log.Trace(item.name, "modTime=%v", modTime)("")
+	item.mu.Lock()
+	defer item.mu.Unlock()
+	fi, err := item._stat()
+	if err == nil {
+		modTime = fi.ModTime()
+	}
+	return modTime, nil
+}
+
 // ReadAt bytes from the file at off
 func (item *Item) ReadAt(b []byte, off int64) (n int, err error) {
 	n = 0