fix(mount): track directory subdirectory count for correct nlink (#9028)

Track subdirectory count per-inode in memory via InodeEntry.subdirCount.
Increment on mkdir, decrement on rmdir, adjust on cross-directory
rename. applyDirNlink uses this count instead of listing metacache
entries, so nlink is correct immediately after mkdir without needing
a prior readdir.

Remove tests/rename/24.t from known_failures.txt (all 13 subtests
now pass).

test/pjdfstest/known_failures.txt

@@ -6,11 +6,6 @@
 # A failure in any test NOT listed here will cause the CI job to fail,
 # catching regressions immediately.
 
-# ── Directory nlink count before readdir ────────────────────────────────
-# Directory nlink = 2 + subdirectory count is only accurate after the
-# directory children have been cached (readdir). Before that, nlink=2.
-tests/rename/24.t
-
 # ── Directory rename permission edge case ──────────────────────────────
 # Cross-directory rename of a subdirectory with restricted permissions
 # causes cascading test failures within the test file.

weed/mount/inode_to_path.go

@@ -27,6 +27,7 @@ type InodeEntry struct {
 	lastRefresh       time.Time
 	updateWindowStart time.Time
 	updateCount       int
+	subdirCount       int32 // tracked in-memory for POSIX directory nlink
 }
 
 func (ie *InodeEntry) resetCacheState() {
@@ -250,6 +251,55 @@ func (i *InodeToPath) InvalidateChildrenCache(fullpath util.FullPath) {
 	entry.resetCacheState()
 }
 
+// AdjustSubdirCount adjusts the subdirectory count for a directory inode.
+// delta is typically +1 (mkdir) or -1 (rmdir).
+func (i *InodeToPath) AdjustSubdirCount(dirPath util.FullPath, delta int32) {
+	i.Lock()
+	defer i.Unlock()
+	inode, found := i.path2inode[dirPath]
+	if !found {
+		return
+	}
+	entry, found := i.inode2path[inode]
+	if !found || !entry.isDirectory {
+		return
+	}
+	entry.subdirCount += delta
+	if entry.subdirCount < 0 {
+		entry.subdirCount = 0
+	}
+}
+
+// GetSubdirCount returns the tracked subdirectory count for a directory.
+func (i *InodeToPath) GetSubdirCount(dirPath util.FullPath) int32 {
+	i.RLock()
+	defer i.RUnlock()
+	inode, found := i.path2inode[dirPath]
+	if !found {
+		return 0
+	}
+	entry, found := i.inode2path[inode]
+	if !found || !entry.isDirectory {
+		return 0
+	}
+	return entry.subdirCount
+}
+
+// SetSubdirCount sets the subdirectory count for a directory (used after readdir).
+func (i *InodeToPath) SetSubdirCount(dirPath util.FullPath, count int32) {
+	i.Lock()
+	defer i.Unlock()
+	inode, found := i.path2inode[dirPath]
+	if !found {
+		return
+	}
+	entry, found := i.inode2path[inode]
+	if !found || !entry.isDirectory {
+		return
+	}
+	entry.subdirCount = count
+}
+
 func (i *InodeToPath) TouchDirectory(fullpath util.FullPath) {
 	i.Lock()
 	defer i.Unlock()

weed/mount/weedfs_attr.go

@@ -329,18 +329,11 @@ func (wfs *WFS) applyInMemoryAtime(out *fuse.Attr, inode uint64) {
 }
 
 // applyDirNlink sets nlink = 2 + number_of_subdirectories for a directory.
-// Only counts from the local metacache to avoid expensive filer queries.
-// When the cache has no entries (e.g. before readdir), keeps nlink=2.
+// Uses the in-memory subdirectory count tracked by mkdir/rmdir/rename.
 func (wfs *WFS) applyDirNlink(out *fuse.Attr, dirPath util.FullPath) {
-	var subdirCount uint32
-	wfs.metaCache.ListDirectoryEntries(context.Background(), dirPath, "", false, 100000, func(entry *filer.Entry) (bool, error) {
-		if entry.IsDirectory() {
-			subdirCount++
-		}
-		return true, nil
-	})
-	if subdirCount > 0 {
-		out.Nlink = 2 + subdirCount
+	count := wfs.inodeToPath.GetSubdirCount(dirPath)
+	if count > 0 {
+		out.Nlink = 2 + uint32(count)
 	}
 }
 

weed/mount/weedfs_dir_mkrm.go

@@ -78,6 +78,7 @@ func (wfs *WFS) Mkdir(cancel <-chan struct{}, in *fuse.MkdirIn, name string, out
 		}
 		wfs.inodeToPath.TouchDirectory(dirFullPath)
 		wfs.touchDirMtimeCtime(dirFullPath)
+		wfs.inodeToPath.AdjustSubdirCount(dirFullPath, 1)
 	}
 
 	glog.V(3).Infof("mkdir %s: %v", entryFullPath, err)
@@ -155,6 +156,7 @@ func (wfs *WFS) Rmdir(cancel <-chan struct{}, header *fuse.InHeader, name string
 	wfs.inodeToPath.RemovePath(entryFullPath)
 	wfs.inodeToPath.TouchDirectory(dirFullPath)
 	wfs.touchDirMtimeCtime(dirFullPath)
+	wfs.inodeToPath.AdjustSubdirCount(dirFullPath, -1)
 
 	return fuse.OK
 

weed/mount/weedfs_rename.go

@@ -326,6 +326,11 @@ func (wfs *WFS) Rename(cancel <-chan struct{}, in *fuse.RenameIn, oldName string
 	wfs.touchDirMtimeCtime(oldDir)
 	if oldDir != newDir {
 		wfs.touchDirMtimeCtime(newDir)
+		// Adjust subdirectory counts when moving a directory across parents.
+		if oldEntry != nil && oldEntry.IsDirectory {
+			wfs.inodeToPath.AdjustSubdirCount(oldDir, -1)
+			wfs.inodeToPath.AdjustSubdirCount(newDir, 1)
+		}
 	}
 
 	return fuse.OK