mount: keep metadata operations working on a removed open directory (#11073)

* mount: remember the entry of a directory removed while still referenced

A directory removed while a descriptor is open on it keeps its inode until
the kernel's final forget, but unlike a file it has no handle to live on
through: OpenDir hands out only a listing cursor. Keep the last-known entry
in memory, keyed by inode, from rmdir until that forget.

Claude-Session: https://claude.ai/code/session_01GYqLENjZzbV5hgt4L8cSAK

* mount: serve metadata ops on a removed open directory from its remembered entry

fchmod, futimens, and the f*xattr calls on a descriptor whose directory was
removed failed with ENOENT: maybeReadEntry resolved the inode to a path, and
rmdir had already dropped it. Fall back to the remembered entry the same way
an unlinked file falls back to its open handle. Mutations publish a changed
copy back rather than editing in place, so a concurrent reader never sees a
half-applied change, and the empty path keeps nlink 0 in every reply.

Claude-Session: https://claude.ai/code/session_01GYqLENjZzbV5hgt4L8cSAK

* mount: stash the entry the delete itself returned, not an earlier snapshot

A chmod landing between Rmdir's entry load and the delete RPC would be
resurrected pre-change: the remembered entry was the earlier local snapshot.
The filer serializes the delete against updates under the path lock and hands
the entry back in the delete event, so prefer that, keeping the local load
for the sticky-bit check and as fallback when no event comes back.

Claude-Session: https://claude.ai/code/session_01GYqLENjZzbV5hgt4L8cSAK

* mount: drop a remembered entry whose insert lost to the final forget

The forget's cleanup runs between RemovePath and the insert when the kernel
evicts the inode concurrently, finds nothing, and the entry would sit in the
map for the life of the mount. Re-check the inode after inserting and take
the entry back out; every interleaving now ends with the map empty.

Claude-Session: https://claude.ai/code/session_01GYqLENjZzbV5hgt4L8cSAK

* mount: insert the remembered entry under the inode table lock

The post-insert HasInode re-check could be fooled by inode number reuse: a
lookup landing between the forget and the check makes the number look alive
and the stale entry stays, keyed to someone else's inode. Do not check after
the fact — RemovePath now runs the retention callback inside its critical
section, where the forget that releases under the same lock cannot have run
and cannot be missed. Publishes need no such fence: their open descriptor
keeps the kernel from issuing the final forget in the first place.

Claude-Session: https://claude.ai/code/session_01GYqLENjZzbV5hgt4L8cSAK

weed/mount/inode_to_path.go

@@ -483,7 +483,12 @@ func (i *InodeToPath) AddPath(inode uint64, path util.FullPath) {
 	}
 }
 
-func (i *InodeToPath) RemovePath(path util.FullPath) {
+// RemovePath drops the name. onStillReferenced, if given, runs under the
+// table's lock when the kernel still holds lookup references to the inode:
+// such an inode keeps receiving requests until the final forget, and holding
+// the lock is what keeps that forget from racing whatever per-inode state the
+// callback installs — Forget releases under the same lock.
+func (i *InodeToPath) RemovePath(path util.FullPath, onStillReferenced func(inode uint64)) {
 	i.Lock()
 	defer i.Unlock()
 	inode, found := i.path2inode[path]
@@ -491,6 +496,9 @@ func (i *InodeToPath) RemovePath(path util.FullPath) {
 		delete(i.path2inode, path)
 		i.dropDirPath(inode)
 		i.removePathFromInode2Path(inode, path)
+		if ie := i.inode2path[inode]; ie != nil && ie.nlookup > 0 && onStillReferenced != nil {
+			onStillReferenced(inode)
+		}
 	}
 }
 

weed/mount/inode_to_path_dirstate_test.go

@@ -56,7 +56,7 @@ func TestDirStateIndexesStayInStep(t *testing.T) {
 		t.Error("renamed directory not indexed")
 	}
 
-	itp.RemovePath("/a/moved")
+	itp.RemovePath("/a/moved", nil)
 	if itp.dirStateOf("/a/moved") != nil {
 		t.Error("removed directory still indexed")
 	}
@@ -77,7 +77,7 @@ func TestForgetDoesNotDropAReusedDirPath(t *testing.T) {
 	now := time.Now().Unix()
 
 	oldInode := itp.Lookup("/a", now, true, false, 0, true)
-	itp.RemovePath("/a")
+	itp.RemovePath("/a", nil)
 	newInode := itp.Lookup("/a", now+1, true, false, 0, true)
 	if newInode == oldInode {
 		t.Fatalf("recreated directory reused inode %d", newInode)

weed/mount/weedfs.go

@@ -177,6 +177,8 @@ type WFS struct {
 	atimeMap              map[uint64]time.Time // inode -> atime, in-memory only, bounded
 	dirMtimeMu            sync.Mutex
 	dirMtimeMap           map[uint64]time.Time // inode -> mtime/ctime, in-memory overlay for dirs
+	removedDirMu          sync.Mutex
+	removedDirs           map[uint64]*filer_pb.Entry // inode -> last-known entry of a directory removed while still referenced
 	entryValidSec         uint64                     // kernel FUSE entry cache TTL in seconds
 	attrValidSec          uint64                     // kernel FUSE attr cache TTL in seconds
 	dirIdleEvict          time.Duration
@@ -524,7 +526,8 @@ func (wfs *WFS) Init(server *fuse.Server) {
 // maybeReadEntry resolves an inode to the entry metadata operations act on. An
 // open handle answers ahead of the path: unlink drops the name while the
 // descriptor stays valid, so an unlinked-but-open file returns its handle's
-// entry with an empty path instead of ENOENT.
+// entry with an empty path instead of ENOENT. A removed directory has no
+// handle; its remembered entry answers the same way.
 func (wfs *WFS) maybeReadEntry(inode uint64) (path util.FullPath, fh *FileHandle, entry *filer_pb.Entry, status fuse.Status) {
 	var found bool
 	if fh, found = wfs.fhMap.FindFileHandle(inode); found {
@@ -538,6 +541,9 @@ func (wfs *WFS) maybeReadEntry(inode uint64) (path util.FullPath, fh *FileHandle
 	}
 	path, status = wfs.inodeToPath.GetPath(inode)
 	if status != fuse.OK {
+		if entry = wfs.removedDirEntry(inode); entry != nil {
+			return "", nil, entry, fuse.OK
+		}
 		return
 	}
 	entry, _, status = wfs.maybeLoadEntry(path)

weed/mount/weedfs_attr.go

@@ -7,6 +7,8 @@ import (
 	"time"
 
 	"github.com/seaweedfs/go-fuse/v2/fuse"
+	"google.golang.org/protobuf/proto"
+
 	"github.com/seaweedfs/seaweedfs/weed/filer"
 	"github.com/seaweedfs/seaweedfs/weed/glog"
 	"github.com/seaweedfs/seaweedfs/weed/pb/filer_pb"
@@ -206,6 +208,11 @@ func (wfs *WFS) SetAttr(cancel <-chan struct{}, input *fuse.SetAttrIn, out *fuse
 		fh.dirtyMetadata = true
 		return fuse.OK
 	}
+	if path == "" {
+		// removed while open: the remembered entry is all there is to update
+		wfs.rememberRemovedDir(input.NodeId, entry)
+		return fuse.OK
+	}
 
 	return wfs.saveEntry(path, entry)
 
@@ -399,10 +406,10 @@ func (wfs *WFS) setAtime(inode uint64, t time.Time) {
 }
 
 // applyInMemoryAtime overlays the in-memory atime onto a fuse.Attr if present.
-// forgetInMemoryTimes drops the overlays for an inode. Both maps are keyed by
+// forgetInMemoryTimes drops the overlays for an inode. All these maps are keyed
-// inode and inodes are derived from the path, so a delete and recreate can
+// by inode and inodes are derived from the path, so a delete and recreate can
 // hand the same number to a different file — which would then inherit the
-// previous one's access or modification time.
+// previous one's access or modification time, or a removed directory's entry.
 func (wfs *WFS) forgetInMemoryTimes(inode uint64) {
 	wfs.atimeMu.Lock()
 	delete(wfs.atimeMap, inode)
@@ -411,6 +418,41 @@ func (wfs *WFS) forgetInMemoryTimes(inode uint64) {
 	wfs.dirMtimeMu.Lock()
 	delete(wfs.dirMtimeMap, inode)
 	wfs.dirMtimeMu.Unlock()
+
+	wfs.removedDirMu.Lock()
+	delete(wfs.removedDirs, inode)
+	wfs.removedDirMu.Unlock()
+}
+
+// rememberRemovedDir keeps the last-known entry of a directory removed while
+// the kernel still references its inode. A directory has no file handle to
+// live on through, so this is what serves fstat/fchmod/f*xattr on a still-open
+// descriptor until the final forget. Mutations publish through here as well,
+// replacing the stored entry wholesale.
+//
+// The final forget's cleanup cannot miss an insert: Rmdir inserts inside
+// RemovePath's callback, under the same inode table lock the forget releases
+// under, and a publish runs inside a request whose open descriptor keeps the
+// kernel from issuing that forget at all.
+func (wfs *WFS) rememberRemovedDir(inode uint64, entry *filer_pb.Entry) {
+	wfs.removedDirMu.Lock()
+	if wfs.removedDirs == nil {
+		wfs.removedDirs = make(map[uint64]*filer_pb.Entry)
+	}
+	wfs.removedDirs[inode] = entry
+	wfs.removedDirMu.Unlock()
+}
+
+// removedDirEntry hands out a private copy: stored entries are never mutated
+// in place, so concurrent readers cannot see a half-applied change.
+func (wfs *WFS) removedDirEntry(inode uint64) *filer_pb.Entry {
+	wfs.removedDirMu.Lock()
+	entry := wfs.removedDirs[inode]
+	wfs.removedDirMu.Unlock()
+	if entry == nil {
+		return nil
+	}
+	return proto.Clone(entry).(*filer_pb.Entry)
 }
 
 func (wfs *WFS) applyInMemoryAtime(out *fuse.Attr, inode uint64) {

weed/mount/weedfs_attr_unlinked_test.go

@@ -1,7 +1,9 @@
 package mount
 
 import (
+	"os"
 	"testing"
+	"time"
 
 	"github.com/seaweedfs/go-fuse/v2/fuse"
 	"github.com/seaweedfs/seaweedfs/weed/filer"
@@ -47,7 +49,7 @@ func newUnlinkedOpenFile(t *testing.T) (*WFS, uint64, *FileHandle) {
 	wfs.fhMap.inode2fh[inode] = fh
 	wfs.fhMap.fh2inode[fh.fh] = inode
 
-	wfs.inodeToPath.RemovePath(fullPath)
+	wfs.inodeToPath.RemovePath(fullPath, nil)
 	fh.isDeleted = true
 
 	return wfs, inode, fh
@@ -138,3 +140,153 @@ func TestXAttrOnUnlinkedOpenFile(t *testing.T) {
 		t.Fatalf("RemoveXAttr on unlinked open file: got %v, want OK", status)
 	}
 }
+
+// newRemovedOpenDir builds a WFS holding one kernel-referenced directory whose
+// name rmdir has already dropped, the state between rmdir() and releasedir().
+func newRemovedOpenDir(t *testing.T) (*WFS, uint64) {
+	t.Helper()
+
+	wfs := &WFS{
+		option:      &Option{},
+		inodeToPath: NewInodeToPath(util.FullPath("/"), 0),
+		fhMap:       NewFileHandleToInode(),
+		fhLockTable: util.NewLockTable[FileHandleId](),
+		atimeMap:    make(map[uint64]time.Time, 8),
+		dirMtimeMap: make(map[uint64]time.Time, 8),
+	}
+
+	const inode = uint64(7)
+	fullPath := util.FullPath("/dir")
+	wfs.inodeToPath.Lookup(fullPath, 1, true, false, inode, true)
+
+	kept := false
+	wfs.inodeToPath.RemovePath(fullPath, func(removedInode uint64) {
+		kept = true
+		wfs.rememberRemovedDir(removedInode, &filer_pb.Entry{
+			Name:        "dir",
+			IsDirectory: true,
+			Attributes:  &filer_pb.FuseAttributes{FileMode: uint32(os.ModeDir | 0755), Uid: 1, Gid: 2},
+		})
+	})
+	if !kept {
+		t.Fatal("RemovePath did not report the inode as still referenced")
+	}
+
+	return wfs, inode
+}
+
+// TestSetAttrOnRemovedOpenDir covers fchmod/futimens on a descriptor whose
+// directory has been removed: the inode lives on until the final forget, so
+// these must not fail with ENOENT, and the change must be visible to a
+// following fstat.
+func TestSetAttrOnRemovedOpenDir(t *testing.T) {
+	wfs, inode := newRemovedOpenDir(t)
+
+	in := &fuse.SetAttrIn{}
+	in.NodeId = inode
+	in.Valid = fuse.FATTR_MODE
+	in.Mode = 0770
+	var out fuse.AttrOut
+	if status := wfs.SetAttr(nil, in, &out); status != fuse.OK {
+		t.Fatalf("SetAttr mode on removed open dir: got %v, want OK", status)
+	}
+	if out.Attr.Mode&0777 != 0770 {
+		t.Fatalf("SetAttr mode: got %o, want 770", out.Attr.Mode&0777)
+	}
+	if out.Attr.Nlink != 0 {
+		t.Fatalf("SetAttr nlink: got %d, want 0", out.Attr.Nlink)
+	}
+
+	in = &fuse.SetAttrIn{}
+	in.NodeId = inode
+	in.Valid = fuse.FATTR_MTIME
+	in.Mtime = 12345
+	if status := wfs.SetAttr(nil, in, &out); status != fuse.OK {
+		t.Fatalf("SetAttr mtime on removed open dir: got %v, want OK", status)
+	}
+
+	gin := &fuse.GetAttrIn{}
+	gin.NodeId = inode
+	if status := wfs.GetAttr(nil, gin, &out); status != fuse.OK {
+		t.Fatalf("GetAttr on removed open dir: got %v, want OK", status)
+	}
+	if out.Attr.Mode&0777 != 0770 {
+		t.Fatalf("GetAttr mode after chmod: got %o, want 770", out.Attr.Mode&0777)
+	}
+	if out.Attr.Mode&fuse.S_IFDIR == 0 {
+		t.Fatalf("GetAttr lost the directory type: %o", out.Attr.Mode)
+	}
+	if out.Attr.Mtime != 12345 {
+		t.Fatalf("GetAttr mtime after utimens: got %d, want 12345", out.Attr.Mtime)
+	}
+	if out.Attr.Uid != 1 || out.Attr.Gid != 2 {
+		t.Fatalf("GetAttr uid/gid: got %d/%d, want 1/2", out.Attr.Uid, out.Attr.Gid)
+	}
+	if out.Attr.Nlink != 0 {
+		t.Fatalf("GetAttr nlink: got %d, want 0", out.Attr.Nlink)
+	}
+}
+
+// TestXAttrOnRemovedOpenDir covers fsetxattr/fgetxattr/fremovexattr on a
+// descriptor whose directory has been removed.
+func TestXAttrOnRemovedOpenDir(t *testing.T) {
+	wfs, inode := newRemovedOpenDir(t)
+
+	setIn := &fuse.SetXAttrIn{}
+	setIn.NodeId = inode
+	if status := wfs.SetXAttr(nil, setIn, "user.k", []byte("v")); status != fuse.OK {
+		t.Fatalf("SetXAttr on removed open dir: got %v, want OK", status)
+	}
+
+	header := &fuse.InHeader{NodeId: inode}
+	dest := make([]byte, 8)
+	n, status := wfs.GetXAttr(nil, header, "user.k", dest)
+	if status != fuse.OK {
+		t.Fatalf("GetXAttr on removed open dir: got %v, want OK", status)
+	}
+	if string(dest[:n]) != "v" {
+		t.Fatalf("GetXAttr value: got %q, want %q", dest[:n], "v")
+	}
+
+	if status := wfs.RemoveXAttr(nil, header, "user.k"); status != fuse.OK {
+		t.Fatalf("RemoveXAttr on removed open dir: got %v, want OK", status)
+	}
+	if _, status := wfs.GetXAttr(nil, header, "user.k", dest); status != fuse.ENOATTR {
+		t.Fatalf("GetXAttr after remove: got %v, want ENOATTR", status)
+	}
+}
+
+// TestForgetReleasesRemovedOpenDir pins the cleanup: once the kernel drops its
+// last reference, the remembered entry goes with it.
+func TestForgetReleasesRemovedOpenDir(t *testing.T) {
+	wfs, inode := newRemovedOpenDir(t)
+
+	wfs.Forget(inode, 1)
+
+	in := &fuse.SetAttrIn{}
+	in.NodeId = inode
+	in.Valid = fuse.FATTR_MODE
+	in.Mode = 0700
+	var out fuse.AttrOut
+	if status := wfs.SetAttr(nil, in, &out); status != fuse.ENOENT {
+		t.Fatalf("SetAttr after forget: got %v, want ENOENT", status)
+	}
+	if len(wfs.removedDirs) != 0 {
+		t.Fatalf("removedDirs not cleaned up: %d entries", len(wfs.removedDirs))
+	}
+}
+
+// TestRemovePathSkipsUnreferencedInode pins the insert-forget ordering: once
+// the kernel's references are gone, RemovePath must not offer the inode for
+// retention, so nothing can be inserted that the forget's cleanup missed.
+func TestRemovePathSkipsUnreferencedInode(t *testing.T) {
+	itp := NewInodeToPath(util.FullPath("/"), 0)
+	fullPath := util.FullPath("/dir")
+	itp.Lookup(fullPath, 1, true, false, 7, true)
+	itp.Forget(7, 1, nil, nil)
+
+	itp.Lookup(fullPath, 1, true, false, 7, false)
+	itp.RemovePath(fullPath, func(inode uint64) {
+		t.Fatalf("RemovePath offered unreferenced inode %d for retention", inode)
+	})
+}

weed/mount/weedfs_dir_mkrm.go

@@ -7,6 +7,7 @@ import (
 	"time"
 
 	"github.com/seaweedfs/go-fuse/v2/fuse"
+	"google.golang.org/protobuf/proto"
 
 	"github.com/seaweedfs/seaweedfs/weed/filer"
 	"github.com/seaweedfs/seaweedfs/weed/glog"
@@ -138,10 +139,15 @@ func (wfs *WFS) Rmdir(cancel <-chan struct{}, header *fuse.InHeader, name string
 	}
 	entryFullPath := dirFullPath.Child(name)
 
+	targetEntry, _, targetCode := wfs.maybeLoadEntry(entryFullPath)
+	if targetCode != fuse.OK {
+		targetEntry = nil
+	}
+
 	// POSIX: enforce sticky bit on the parent directory.
 	if dirEntry, _, dirCode := wfs.maybeLoadEntry(dirFullPath); dirCode == fuse.OK && dirEntry != nil && dirEntry.Attributes != nil {
 		targetUid := uint32(0)
-		if targetEntry, _, targetCode := wfs.maybeLoadEntry(entryFullPath); targetCode == fuse.OK && targetEntry != nil && targetEntry.Attributes != nil {
+		if targetEntry != nil && targetEntry.Attributes != nil {
 			targetUid = targetEntry.Attributes.Uid
 		}
 		if code := checkStickyBit(dirEntry.Attributes.FileMode, dirEntry.Attributes.Uid, targetUid, header.Uid); code != fuse.OK {
@@ -174,7 +180,17 @@ func (wfs *WFS) Rmdir(cancel <-chan struct{}, header *fuse.InHeader, name string
 		glog.Warningf("rmdir %s: best-effort metadata apply failed: %v", entryFullPath, applyErr)
 		wfs.inodeToPath.InvalidateChildrenCache(dirFullPath)
 	}
-	wfs.inodeToPath.RemovePath(entryFullPath)
+	// The filer serialized the delete against concurrent updates and returned
+	// the entry as it stood; the snapshot loaded above may predate one.
+	if oldEntry := resp.GetMetadataEvent().GetEventNotification().GetOldEntry(); oldEntry.GetAttributes() != nil {
+		targetEntry = proto.Clone(oldEntry).(*filer_pb.Entry)
+		wfs.mapPbIdFromFilerToLocal(targetEntry)
+	}
+	wfs.inodeToPath.RemovePath(entryFullPath, func(inode uint64) {
+		if targetEntry != nil {
+			wfs.rememberRemovedDir(inode, targetEntry)
+		}
+	})
 	wfs.inodeToPath.TouchDirectory(dirFullPath)
 	wfs.touchDirMtimeCtimeBest(dirFullPath)
 	wfs.inodeToPath.AdjustSubdirCount(dirFullPath, -1)

weed/mount/weedfs_file_mkrm.go

@@ -302,7 +302,7 @@ func (wfs *WFS) Unlink(cancel <-chan struct{}, header *fuse.InHeader, name strin
 		}
 	}
 
-	wfs.inodeToPath.RemovePath(entryFullPath)
+	wfs.inodeToPath.RemovePath(entryFullPath, nil)
 
 	if isHardLink && sharedInode != 0 {
 		decremented := proto.Clone(entry).(*filer_pb.Entry)

weed/mount/weedfs_xattr.go

@@ -141,6 +141,11 @@ func (wfs *WFS) SetXAttr(cancel <-chan struct{}, input *fuse.SetXAttrIn, attr st
 		fh.dirtyMetadata = true
 		return fuse.OK
 	}
+	if path == "" {
+		// removed while open: the remembered entry is all there is to update
+		wfs.rememberRemovedDir(input.NodeId, entry)
+		return fuse.OK
+	}
 
 	return wfs.saveEntry(path, entry)
 
@@ -219,6 +224,11 @@ func (wfs *WFS) RemoveXAttr(cancel <-chan struct{}, header *fuse.InHeader, attr
 		fh.dirtyMetadata = true
 		return fuse.OK
 	}
+	if path == "" {
+		// removed while open: the remembered entry is all there is to update
+		wfs.rememberRemovedDir(header.NodeId, entry)
+		return fuse.OK
+	}
 
 	return wfs.saveEntry(path, entry)
 }