Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

Pull vfs pile 2 (of many) from Al Viro: "Mostly Miklos' series this time" * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: constify dcache.c inlined helpers where possible fuse: drop dentry on failed revalidate fuse: clean up return in fuse_dentry_revalidate() fuse: use d_materialise_unique() sysfs: use check_submounts_and_drop() nfs: use check_submounts_and_drop() gfs2: use check_submounts_and_drop() afs: use check_submounts_and_drop() vfs: check unlinked ancestors before mount vfs: check submounts and drop atomically vfs: add d_walk() vfs: restructure d_genocide()
2013-09-07 14:36:57 -07:00 · 2013-09-07 14:36:57 -07:00 · dc0755cdb1
parent c7c4591db6 f0d3b3ded9
commit dc0755cdb1
9 changed files with 326 additions and 261 deletions
--- a/fs/afs/dir.c
+++ b/fs/afs/dir.c
@ -685,16 +685,12 @@ static int afs_d_revalidate(struct dentry *dentry, unsigned int flags)
 	spin_unlock(&dentry->d_lock);

 out_bad:
-	if (dentry->d_inode) {
-		/* don't unhash if we have submounts */
-		if (have_submounts(dentry))
-			goto out_skip;
-	}
+	/* don't unhash if we have submounts */
+	if (check_submounts_and_drop(dentry) != 0)
+		goto out_skip;

 	_debug("dropping dentry %s/%s",
 	       parent->d_name.name, dentry->d_name.name);
-	shrink_dcache_parent(dentry);
-	d_drop(dentry);
 	dput(parent);
 	key_put(key);

--- a/fs/dcache.c
+++ b/fs/dcache.c
@ -1031,34 +1031,56 @@ static struct dentry *try_to_ascend(struct dentry *old, int locked, unsigned seq
 	return new;
 }

-
-/*
- * Search for at least 1 mount point in the dentry's subdirs.
- * We descend to the next level whenever the d_subdirs
- * list is non-empty and continue searching.
- */
- 
 /**
- * have_submounts - check for mounts over a dentry
- * @parent: dentry to check.
- *
- * Return true if the parent or its subdirectories contain
- * a mount point
+ * enum d_walk_ret - action to talke during tree walk
+ * @D_WALK_CONTINUE:	contrinue walk
+ * @D_WALK_QUIT:	quit walk
+ * @D_WALK_NORETRY:	quit when retry is needed
+ * @D_WALK_SKIP:	skip this dentry and its children
 */
-int have_submounts(struct dentry *parent)
+enum d_walk_ret {
+	D_WALK_CONTINUE,
+	D_WALK_QUIT,
+	D_WALK_NORETRY,
+	D_WALK_SKIP,
+};
+
+/**
+ * d_walk - walk the dentry tree
+ * @parent:	start of walk
+ * @data:	data passed to @enter() and @finish()
+ * @enter:	callback when first entering the dentry
+ * @finish:	callback when successfully finished the walk
+ *
+ * The @enter() and @finish() callbacks are called with d_lock held.
+ */
+static void d_walk(struct dentry *parent, void *data,
+		   enum d_walk_ret (*enter)(void *, struct dentry *),
+		   void (*finish)(void *))
 {
 	struct dentry *this_parent;
 	struct list_head *next;
 	unsigned seq;
 	int locked = 0;
+	enum d_walk_ret ret;
+	bool retry = true;

 	seq = read_seqbegin(&rename_lock);
 again:
 	this_parent = parent;
-
-	if (d_mountpoint(parent))
-		goto positive;
 	spin_lock(&this_parent->d_lock);
+
+	ret = enter(data, this_parent);
+	switch (ret) {
+	case D_WALK_CONTINUE:
+		break;
+	case D_WALK_QUIT:
+	case D_WALK_SKIP:
+		goto out_unlock;
+	case D_WALK_NORETRY:
+		retry = false;
+		break;
+	}
 repeat:
 	next = this_parent->d_subdirs.next;
 resume:
@ -1068,12 +1090,22 @@ int have_submounts(struct dentry *parent)
 		next = tmp->next;

 		spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
-		/* Have we found a mount point ? */
-		if (d_mountpoint(dentry)) {
+
+		ret = enter(data, dentry);
+		switch (ret) {
+		case D_WALK_CONTINUE:
+			break;
+		case D_WALK_QUIT:
 			spin_unlock(&dentry->d_lock);
-			spin_unlock(&this_parent->d_lock);
-			goto positive;
+			goto out_unlock;
+		case D_WALK_NORETRY:
+			retry = false;
+			break;
+		case D_WALK_SKIP:
+			spin_unlock(&dentry->d_lock);
+			continue;
 		}
+
 		if (!list_empty(&dentry->d_subdirs)) {
 			spin_unlock(&this_parent->d_lock);
 			spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_);
@ -1094,28 +1126,96 @@ int have_submounts(struct dentry *parent)
 		next = child->d_u.d_child.next;
 		goto resume;
 	}
+	if (!locked && read_seqretry(&rename_lock, seq)) {
+		spin_unlock(&this_parent->d_lock);
+		goto rename_retry;
+	}
+	if (finish)
+		finish(data);
+
+out_unlock:
 	spin_unlock(&this_parent->d_lock);
-	if (!locked && read_seqretry(&rename_lock, seq))
-		goto rename_retry;
 	if (locked)
 		write_sequnlock(&rename_lock);
-	return 0; /* No mount points found in tree */
-positive:
-	if (!locked && read_seqretry(&rename_lock, seq))
-		goto rename_retry;
-	if (locked)
-		write_sequnlock(&rename_lock);
-	return 1;
+	return;

 rename_retry:
+	if (!retry)
+		return;
 	if (locked)
 		goto again;
 	locked = 1;
 	write_seqlock(&rename_lock);
 	goto again;
 }
+
+/*
+ * Search for at least 1 mount point in the dentry's subdirs.
+ * We descend to the next level whenever the d_subdirs
+ * list is non-empty and continue searching.
+ */
+
+/**
+ * have_submounts - check for mounts over a dentry
+ * @parent: dentry to check.
+ *
+ * Return true if the parent or its subdirectories contain
+ * a mount point
+ */
+
+static enum d_walk_ret check_mount(void *data, struct dentry *dentry)
+{
+	int *ret = data;
+	if (d_mountpoint(dentry)) {
+		*ret = 1;
+		return D_WALK_QUIT;
+	}
+	return D_WALK_CONTINUE;
+}
+
+int have_submounts(struct dentry *parent)
+{
+	int ret = 0;
+
+	d_walk(parent, &ret, check_mount, NULL);
+
+	return ret;
+}
 EXPORT_SYMBOL(have_submounts);

+/*
+ * Called by mount code to set a mountpoint and check if the mountpoint is
+ * reachable (e.g. NFS can unhash a directory dentry and then the complete
+ * subtree can become unreachable).
+ *
+ * Only one of check_submounts_and_drop() and d_set_mounted() must succeed.  For
+ * this reason take rename_lock and d_lock on dentry and ancestors.
+ */
+int d_set_mounted(struct dentry *dentry)
+{
+	struct dentry *p;
+	int ret = -ENOENT;
+	write_seqlock(&rename_lock);
+	for (p = dentry->d_parent; !IS_ROOT(p); p = p->d_parent) {
+		/* Need exclusion wrt. check_submounts_and_drop() */
+		spin_lock(&p->d_lock);
+		if (unlikely(d_unhashed(p))) {
+			spin_unlock(&p->d_lock);
+			goto out;
+		}
+		spin_unlock(&p->d_lock);
+	}
+	spin_lock(&dentry->d_lock);
+	if (!d_unlinked(dentry)) {
+		dentry->d_flags |= DCACHE_MOUNTED;
+		ret = 0;
+	}
+ 	spin_unlock(&dentry->d_lock);
+out:
+	write_sequnlock(&rename_lock);
+	return ret;
+}
+
 /*
 * Search the dentry child list of the specified parent,
 * and move any unused dentries to the end of the unused
@ -1130,93 +1230,46 @@ EXPORT_SYMBOL(have_submounts);
 * drop the lock and return early due to latency
 * constraints.
 */
-static int select_parent(struct dentry *parent, struct list_head *dispose)
+
+struct select_data {
+	struct dentry *start;
+	struct list_head dispose;
+	int found;
+};
+
+static enum d_walk_ret select_collect(void *_data, struct dentry *dentry)
 {
-	struct dentry *this_parent;
-	struct list_head *next;
-	unsigned seq;
-	int found = 0;
-	int locked = 0;
+	struct select_data *data = _data;
+	enum d_walk_ret ret = D_WALK_CONTINUE;

-	seq = read_seqbegin(&rename_lock);
-again:
-	this_parent = parent;
-	spin_lock(&this_parent->d_lock);
-repeat:
-	next = this_parent->d_subdirs.next;
-resume:
-	while (next != &this_parent->d_subdirs) {
-		struct list_head *tmp = next;
-		struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
-		next = tmp->next;
+	if (data->start == dentry)
+		goto out;

-		spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
-
-		/*
-		 * move only zero ref count dentries to the dispose list.
-		 *
-		 * Those which are presently on the shrink list, being processed
-		 * by shrink_dentry_list(), shouldn't be moved.  Otherwise the
-		 * loop in shrink_dcache_parent() might not make any progress
-		 * and loop forever.
-		 */
-		if (dentry->d_lockref.count) {
-			dentry_lru_del(dentry);
-		} else if (!(dentry->d_flags & DCACHE_SHRINK_LIST)) {
-			dentry_lru_move_list(dentry, dispose);
-			dentry->d_flags |= DCACHE_SHRINK_LIST;
-			found++;
-		}
-		/*
-		 * We can return to the caller if we have found some (this
-		 * ensures forward progress). We'll be coming back to find
-		 * the rest.
-		 */
-		if (found && need_resched()) {
-			spin_unlock(&dentry->d_lock);
-			goto out;
-		}
-
-		/*
-		 * Descend a level if the d_subdirs list is non-empty.
-		 */
-		if (!list_empty(&dentry->d_subdirs)) {
-			spin_unlock(&this_parent->d_lock);
-			spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_);
-			this_parent = dentry;
-			spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
-			goto repeat;
-		}
-
-		spin_unlock(&dentry->d_lock);
+	/*
+	 * move only zero ref count dentries to the dispose list.
+	 *
+	 * Those which are presently on the shrink list, being processed
+	 * by shrink_dentry_list(), shouldn't be moved.  Otherwise the
+	 * loop in shrink_dcache_parent() might not make any progress
+	 * and loop forever.
+	 */
+	if (dentry->d_lockref.count) {
+		dentry_lru_del(dentry);
+	} else if (!(dentry->d_flags & DCACHE_SHRINK_LIST)) {
+		dentry_lru_move_list(dentry, &data->dispose);
+		dentry->d_flags |= DCACHE_SHRINK_LIST;
+		data->found++;
+		ret = D_WALK_NORETRY;
 	}
 	/*
-	 * All done at this level ... ascend and resume the search.
+	 * We can return to the caller if we have found some (this
+	 * ensures forward progress). We'll be coming back to find
+	 * the rest.
 	 */
-	if (this_parent != parent) {
-		struct dentry *child = this_parent;
-		this_parent = try_to_ascend(this_parent, locked, seq);
-		if (!this_parent)
-			goto rename_retry;
-		next = child->d_u.d_child.next;
-		goto resume;
-	}
+	if (data->found && need_resched())
+		ret = D_WALK_QUIT;
 out:
-	spin_unlock(&this_parent->d_lock);
-	if (!locked && read_seqretry(&rename_lock, seq))
-		goto rename_retry;
-	if (locked)
-		write_sequnlock(&rename_lock);
-	return found;
-
-rename_retry:
-	if (found)
-		return found;
-	if (locked)
-		goto again;
-	locked = 1;
-	write_seqlock(&rename_lock);
-	goto again;
+	return ret;
 }

 /**
@ -1225,18 +1278,90 @@ static int select_parent(struct dentry *parent, struct list_head *dispose)
 *
 * Prune the dcache to remove unused children of the parent dentry.
 */
-void shrink_dcache_parent(struct dentry * parent)
+void shrink_dcache_parent(struct dentry *parent)
 {
-	LIST_HEAD(dispose);
-	int found;
+	for (;;) {
+		struct select_data data;

-	while ((found = select_parent(parent, &dispose)) != 0) {
-		shrink_dentry_list(&dispose);
+		INIT_LIST_HEAD(&data.dispose);
+		data.start = parent;
+		data.found = 0;
+
+		d_walk(parent, &data, select_collect, NULL);
+		if (!data.found)
+			break;
+
+		shrink_dentry_list(&data.dispose);
 		cond_resched();
 	}
 }
 EXPORT_SYMBOL(shrink_dcache_parent);

+static enum d_walk_ret check_and_collect(void *_data, struct dentry *dentry)
+{
+	struct select_data *data = _data;
+
+	if (d_mountpoint(dentry)) {
+		data->found = -EBUSY;
+		return D_WALK_QUIT;
+	}
+
+	return select_collect(_data, dentry);
+}
+
+static void check_and_drop(void *_data)
+{
+	struct select_data *data = _data;
+
+	if (d_mountpoint(data->start))
+		data->found = -EBUSY;
+	if (!data->found)
+		__d_drop(data->start);
+}
+
+/**
+ * check_submounts_and_drop - prune dcache, check for submounts and drop
+ *
+ * All done as a single atomic operation relative to has_unlinked_ancestor().
+ * Returns 0 if successfully unhashed @parent.  If there were submounts then
+ * return -EBUSY.
+ *
+ * @dentry: dentry to prune and drop
+ */
+int check_submounts_and_drop(struct dentry *dentry)
+{
+	int ret = 0;
+
+	/* Negative dentries can be dropped without further checks */
+	if (!dentry->d_inode) {
+		d_drop(dentry);
+		goto out;
+	}
+
+	for (;;) {
+		struct select_data data;
+
+		INIT_LIST_HEAD(&data.dispose);
+		data.start = dentry;
+		data.found = 0;
+
+		d_walk(dentry, &data, check_and_collect, check_and_drop);
+		ret = data.found;
+
+		if (!list_empty(&data.dispose))
+			shrink_dentry_list(&data.dispose);
+
+		if (ret <= 0)
+			break;
+
+		cond_resched();
+	}
+
+out:
+	return ret;
+}
+EXPORT_SYMBOL(check_submounts_and_drop);
+
 /**
 * __d_alloc	-	allocate a dcache entry
 * @sb: filesystem it will belong to
@ -2928,68 +3053,24 @@ int is_subdir(struct dentry *new_dentry, struct dentry *old_dentry)
 	return result;
 }

-void d_genocide(struct dentry *root)
+static enum d_walk_ret d_genocide_kill(void *data, struct dentry *dentry)
 {
-	struct dentry *this_parent;
-	struct list_head *next;
-	unsigned seq;
-	int locked = 0;
+	struct dentry *root = data;
+	if (dentry != root) {
+		if (d_unhashed(dentry) || !dentry->d_inode)
+			return D_WALK_SKIP;

-	seq = read_seqbegin(&rename_lock);
-again:
-	this_parent = root;
-	spin_lock(&this_parent->d_lock);
-repeat:
-	next = this_parent->d_subdirs.next;
-resume:
-	while (next != &this_parent->d_subdirs) {
-		struct list_head *tmp = next;
-		struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
-		next = tmp->next;
-
-		spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
-		if (d_unhashed(dentry) || !dentry->d_inode) {
-			spin_unlock(&dentry->d_lock);
-			continue;
-		}
-		if (!list_empty(&dentry->d_subdirs)) {
-			spin_unlock(&this_parent->d_lock);
-			spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_);
-			this_parent = dentry;
-			spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
-			goto repeat;
-		}
 		if (!(dentry->d_flags & DCACHE_GENOCIDE)) {
 			dentry->d_flags |= DCACHE_GENOCIDE;
 			dentry->d_lockref.count--;
 		}
-		spin_unlock(&dentry->d_lock);
 	}
-	if (this_parent != root) {
-		struct dentry *child = this_parent;
-		if (!(this_parent->d_flags & DCACHE_GENOCIDE)) {
-			this_parent->d_flags |= DCACHE_GENOCIDE;
-			this_parent->d_lockref.count--;
-		}
-		this_parent = try_to_ascend(this_parent, locked, seq);
-		if (!this_parent)
-			goto rename_retry;
-		next = child->d_u.d_child.next;
-		goto resume;
-	}
-	spin_unlock(&this_parent->d_lock);
-	if (!locked && read_seqretry(&rename_lock, seq))
-		goto rename_retry;
-	if (locked)
-		write_sequnlock(&rename_lock);
-	return;
+	return D_WALK_CONTINUE;
+}

-rename_retry:
-	if (locked)
-		goto again;
-	locked = 1;
-	write_seqlock(&rename_lock);
-	goto again;
+void d_genocide(struct dentry *parent)
+{
+	d_walk(parent, parent, d_genocide_kill, NULL);
 }

 void d_tmpfile(struct dentry *dentry, struct inode *inode)
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@ -182,10 +182,11 @@ static int fuse_dentry_revalidate(struct dentry *entry, unsigned int flags)
 	struct inode *inode;
 	struct dentry *parent;
 	struct fuse_conn *fc;
+	int ret;

 	inode = ACCESS_ONCE(entry->d_inode);
 	if (inode && is_bad_inode(inode))
-		return 0;
+		goto invalid;
 	else if (fuse_dentry_time(entry) < get_jiffies_64()) {
 		int err;
 		struct fuse_entry_out outarg;
@ -195,20 +196,23 @@ static int fuse_dentry_revalidate(struct dentry *entry, unsigned int flags)

 		/* For negative dentries, always do a fresh lookup */
 		if (!inode)
-			return 0;
+			goto invalid;

+		ret = -ECHILD;
 		if (flags & LOOKUP_RCU)
-			return -ECHILD;
+			goto out;

 		fc = get_fuse_conn(inode);
 		req = fuse_get_req_nopages(fc);
+		ret = PTR_ERR(req);
 		if (IS_ERR(req))
-			return 0;
+			goto out;

 		forget = fuse_alloc_forget();
 		if (!forget) {
 			fuse_put_request(fc, req);
-			return 0;
+			ret = -ENOMEM;
+			goto out;
 		}

 		attr_version = fuse_get_attr_version(fc);
@ -227,7 +231,7 @@ static int fuse_dentry_revalidate(struct dentry *entry, unsigned int flags)
 			struct fuse_inode *fi = get_fuse_inode(inode);
 			if (outarg.nodeid != get_node_id(inode)) {
 				fuse_queue_forget(fc, forget, outarg.nodeid, 1);
-				return 0;
+				goto invalid;
 			}
 			spin_lock(&fc->lock);
 			fi->nlookup++;
@ -235,7 +239,7 @@ static int fuse_dentry_revalidate(struct dentry *entry, unsigned int flags)
 		}
 		kfree(forget);
 		if (err || (outarg.attr.mode ^ inode->i_mode) & S_IFMT)
-			return 0;
+			goto invalid;

 		fuse_change_attributes(inode, &outarg.attr,
 				       entry_attr_timeout(&outarg),
@ -249,7 +253,15 @@ static int fuse_dentry_revalidate(struct dentry *entry, unsigned int flags)
 			dput(parent);
 		}
 	}
-	return 1;
+	ret = 1;
+out:
+	return ret;
+
+invalid:
+	ret = 0;
+	if (check_submounts_and_drop(entry) != 0)
+		ret = 1;
+	goto out;
 }

 static int invalid_nodeid(u64 nodeid)
@ -267,26 +279,6 @@ int fuse_valid_type(int m)
 		S_ISBLK(m) || S_ISFIFO(m) || S_ISSOCK(m);
 }

-/*
- * Add a directory inode to a dentry, ensuring that no other dentry
- * refers to this inode.  Called with fc->inst_mutex.
- */
-static struct dentry *fuse_d_add_directory(struct dentry *entry,
-					   struct inode *inode)
-{
-	struct dentry *alias = d_find_alias(inode);
-	if (alias && !(alias->d_flags & DCACHE_DISCONNECTED)) {
-		/* This tries to shrink the subtree below alias */
-		fuse_invalidate_entry(alias);
-		dput(alias);
-		if (!hlist_empty(&inode->i_dentry))
-			return ERR_PTR(-EBUSY);
-	} else {
-		dput(alias);
-	}
-	return d_splice_alias(inode, entry);
-}
-
 int fuse_lookup_name(struct super_block *sb, u64 nodeid, struct qstr *name,
 		     struct fuse_entry_out *outarg, struct inode **inode)
 {
@ -345,6 +337,24 @@ int fuse_lookup_name(struct super_block *sb, u64 nodeid, struct qstr *name,
 	return err;
 }

+static struct dentry *fuse_materialise_dentry(struct dentry *dentry,
+					      struct inode *inode)
+{
+	struct dentry *newent;
+
+	if (inode && S_ISDIR(inode->i_mode)) {
+		struct fuse_conn *fc = get_fuse_conn(inode);
+
+		mutex_lock(&fc->inst_mutex);
+		newent = d_materialise_unique(dentry, inode);
+		mutex_unlock(&fc->inst_mutex);
+	} else {
+		newent = d_materialise_unique(dentry, inode);
+	}
+
+	return newent;
+}
+
 static struct dentry *fuse_lookup(struct inode *dir, struct dentry *entry,
 				  unsigned int flags)
 {
@ -352,7 +362,6 @@ static struct dentry *fuse_lookup(struct inode *dir, struct dentry *entry,
 	struct fuse_entry_out outarg;
 	struct inode *inode;
 	struct dentry *newent;
-	struct fuse_conn *fc = get_fuse_conn(dir);
 	bool outarg_valid = true;

 	err = fuse_lookup_name(dir->i_sb, get_node_id(dir), &entry->d_name,
@ -368,16 +377,10 @@ static struct dentry *fuse_lookup(struct inode *dir, struct dentry *entry,
 	if (inode && get_node_id(inode) == FUSE_ROOT_ID)
 		goto out_iput;

-	if (inode && S_ISDIR(inode->i_mode)) {
-		mutex_lock(&fc->inst_mutex);
-		newent = fuse_d_add_directory(entry, inode);
-		mutex_unlock(&fc->inst_mutex);
-		err = PTR_ERR(newent);
-		if (IS_ERR(newent))
-			goto out_iput;
-	} else {
-		newent = d_splice_alias(inode, entry);
-	}
+	newent = fuse_materialise_dentry(entry, inode);
+	err = PTR_ERR(newent);
+	if (IS_ERR(newent))
+		goto out_err;

 	entry = newent ? newent : entry;
 	if (outarg_valid)
@ -1275,18 +1278,10 @@ static int fuse_direntplus_link(struct file *file,
 	if (!inode)
 		goto out;

-	if (S_ISDIR(inode->i_mode)) {
-		mutex_lock(&fc->inst_mutex);
-		alias = fuse_d_add_directory(dentry, inode);
-		mutex_unlock(&fc->inst_mutex);
-		err = PTR_ERR(alias);
-		if (IS_ERR(alias)) {
-			iput(inode);
-			goto out;
-		}
-	} else {
-		alias = d_splice_alias(inode, dentry);
-	}
+	alias = fuse_materialise_dentry(dentry, inode);
+	err = PTR_ERR(alias);
+	if (IS_ERR(alias))
+		goto out;

 	if (alias) {
 		dput(dentry);
--- a/fs/gfs2/dentry.c
+++ b/fs/gfs2/dentry.c
@ -93,12 +93,9 @@ static int gfs2_drevalidate(struct dentry *dentry, unsigned int flags)
 	if (!had_lock)
 		gfs2_glock_dq_uninit(&d_gh);
 invalid:
-	if (inode && S_ISDIR(inode->i_mode)) {
-		if (have_submounts(dentry))
-			goto valid;
-		shrink_dcache_parent(dentry);
-	}
-	d_drop(dentry);
+	if (check_submounts_and_drop(dentry) != 0)
+		goto valid;
+
 	dput(parent);
 	return 0;

--- a/fs/internal.h
+++ b/fs/internal.h
@ -126,6 +126,7 @@ extern int invalidate_inodes(struct super_block *, bool);
 * dcache.c
 */
 extern struct dentry *__d_alloc(struct super_block *, const struct qstr *);
+extern int d_set_mounted(struct dentry *dentry);

 /*
 * read_write.c
--- a/fs/namespace.c
+++ b/fs/namespace.c
@ -611,6 +611,7 @@ static struct mountpoint *new_mountpoint(struct dentry *dentry)
 {
 	struct list_head *chain = mountpoint_hashtable + hash(NULL, dentry);
 	struct mountpoint *mp;
+	int ret;

 	list_for_each_entry(mp, chain, m_hash) {
 		if (mp->m_dentry == dentry) {
@ -626,14 +627,12 @@ static struct mountpoint *new_mountpoint(struct dentry *dentry)
 	if (!mp)
 		return ERR_PTR(-ENOMEM);

-	spin_lock(&dentry->d_lock);
-	if (d_unlinked(dentry)) {
-		spin_unlock(&dentry->d_lock);
+	ret = d_set_mounted(dentry);
+	if (ret) {
 		kfree(mp);
-		return ERR_PTR(-ENOENT);
+		return ERR_PTR(ret);
 	}
-	dentry->d_flags |= DCACHE_MOUNTED;
-	spin_unlock(&dentry->d_lock);
+
 	mp->m_dentry = dentry;
 	mp->m_count = 1;
 	list_add(&mp->m_hash, chain);
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@ -1135,14 +1135,13 @@ static int nfs_lookup_revalidate(struct dentry *dentry, unsigned int flags)
 	if (inode && S_ISDIR(inode->i_mode)) {
 		/* Purge readdir caches. */
 		nfs_zap_caches(inode);
-		/* If we have submounts, don't unhash ! */
-		if (have_submounts(dentry))
-			goto out_valid;
 		if (dentry->d_flags & DCACHE_DISCONNECTED)
 			goto out_valid;
-		shrink_dcache_parent(dentry);
 	}
-	d_drop(dentry);
+	/* If we have submounts, don't unhash ! */
+	if (check_submounts_and_drop(dentry) != 0)
+		goto out_valid;
+
 	dput(parent);
 	dfprintk(LOOKUPCACHE, "NFS: %s(%s/%s) is invalid\n",
 			__func__, dentry->d_parent->d_name.name,
--- a/fs/sysfs/dir.c
+++ b/fs/sysfs/dir.c
@ -297,7 +297,6 @@ static int sysfs_dentry_delete(const struct dentry *dentry)
 static int sysfs_dentry_revalidate(struct dentry *dentry, unsigned int flags)
 {
 	struct sysfs_dirent *sd;
-	int is_dir;
 	int type;

 	if (flags & LOOKUP_RCU)
@ -341,18 +340,15 @@ static int sysfs_dentry_revalidate(struct dentry *dentry, unsigned int flags)
 	 * is performed at its new name the dentry will be readded
 	 * to the dcache hashes.
 	 */
-	is_dir = (sysfs_type(sd) == SYSFS_DIR);
 	mutex_unlock(&sysfs_mutex);
-	if (is_dir) {
-		/* If we have submounts we must allow the vfs caches
-		 * to lie about the state of the filesystem to prevent
-		 * leaks and other nasty things.
-		 */
-		if (have_submounts(dentry))
-			goto out_valid;
-		shrink_dcache_parent(dentry);
-	}
-	d_drop(dentry);
+
+	/* If we have submounts we must allow the vfs caches
+	 * to lie about the state of the filesystem to prevent
+	 * leaks and other nasty things.
+	 */
+	if (check_submounts_and_drop(dentry) != 0)
+		goto out_valid;
+
 	return 0;
 }

--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@ -212,7 +212,7 @@ struct dentry_operations {

 extern seqlock_t rename_lock;

-static inline int dname_external(struct dentry *dentry)
+static inline int dname_external(const struct dentry *dentry)
 {
 	return dentry->d_name.name != dentry->d_iname;
 }
@ -253,6 +253,7 @@ extern void d_prune_aliases(struct inode *);

 /* test whether we have any submounts in a subdir tree */
 extern int have_submounts(struct dentry *);
+extern int check_submounts_and_drop(struct dentry *);

 /*
 * This adds the entry to the hash queues.
@ -357,17 +358,17 @@ extern struct dentry *dget_parent(struct dentry *dentry);
 *	Returns true if the dentry passed is not currently hashed.
 */
 
-static inline int d_unhashed(struct dentry *dentry)
+static inline int d_unhashed(const struct dentry *dentry)
 {
 	return hlist_bl_unhashed(&dentry->d_hash);
 }

-static inline int d_unlinked(struct dentry *dentry)
+static inline int d_unlinked(const struct dentry *dentry)
 {
 	return d_unhashed(dentry) && !IS_ROOT(dentry);
 }

-static inline int cant_mount(struct dentry *dentry)
+static inline int cant_mount(const struct dentry *dentry)
 {
 	return (dentry->d_flags & DCACHE_CANT_MOUNT);
 }
@ -381,12 +382,12 @@ static inline void dont_mount(struct dentry *dentry)

 extern void dput(struct dentry *);

-static inline bool d_managed(struct dentry *dentry)
+static inline bool d_managed(const struct dentry *dentry)
 {
 	return dentry->d_flags & DCACHE_MANAGED_DENTRY;
 }

-static inline bool d_mountpoint(struct dentry *dentry)
+static inline bool d_mountpoint(const struct dentry *dentry)
 {
 	return dentry->d_flags & DCACHE_MOUNTED;
 }