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

Pull overlayfs updates from Miklos Szeredi:
 "This work from Amir adds NFS export capability to overlayfs. NFS
  exporting an overlay filesystem is a challange because we want to keep
  track of any copy-up of a file or directory between encoding the file
  handle and decoding it.

  This is achieved by indexing copied up objects by lower layer file
  handle. The index is already used for hard links, this patchset
  extends the use to NFS file handle decoding"

* 'overlayfs-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs: (51 commits)
  ovl: check ERR_PTR() return value from ovl_encode_fh()
  ovl: fix regression in fsnotify of overlay merge dir
  ovl: wire up NFS export operations
  ovl: lookup indexed ancestor of lower dir
  ovl: lookup connected ancestor of dir in inode cache
  ovl: hash non-indexed dir by upper inode for NFS export
  ovl: decode pure lower dir file handles
  ovl: decode indexed dir file handles
  ovl: decode lower file handles of unlinked but open files
  ovl: decode indexed non-dir file handles
  ovl: decode lower non-dir file handles
  ovl: encode lower file handles
  ovl: copy up before encoding non-connectable dir file handle
  ovl: encode non-indexed upper file handles
  ovl: decode connected upper dir file handles
  ovl: decode pure upper file handles
  ovl: encode pure upper file handles
  ovl: document NFS export
  vfs: factor out helpers d_instantiate_anon() and d_alloc_anon()
  ovl: store 'has_upper' and 'opaque' as bit flags
  ...

13 files changed, 1800 insertions, 406 deletions

diff --git a/fs/dcache.c b/fs/dcache.c
index cca2b377ff0a..7c38f39958bc 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1698,9 +1698,15 @@ struct dentry *d_alloc(struct dentry * parent, const struct qstr *name)
 }
 EXPORT_SYMBOL(d_alloc);
 
+struct dentry *d_alloc_anon(struct super_block *sb)
+{
+	return __d_alloc(sb, NULL);
+}
+EXPORT_SYMBOL(d_alloc_anon);
+
 struct dentry *d_alloc_cursor(struct dentry * parent)
 {
-	struct dentry *dentry = __d_alloc(parent->d_sb, NULL);
+	struct dentry *dentry = d_alloc_anon(parent->d_sb);
 	if (dentry) {
 		dentry->d_flags |= DCACHE_RCUACCESS | DCACHE_DENTRY_CURSOR;
 		dentry->d_parent = dget(parent);
@@ -1886,7 +1892,7 @@ struct dentry *d_make_root(struct inode *root_inode)
 	struct dentry *res = NULL;
 
 	if (root_inode) {
-		res = __d_alloc(root_inode->i_sb, NULL);
+		res = d_alloc_anon(root_inode->i_sb);
 		if (res)
 			d_instantiate(res, root_inode);
 		else
@@ -1925,33 +1931,19 @@ struct dentry *d_find_any_alias(struct inode *inode)
 }
 EXPORT_SYMBOL(d_find_any_alias);
 
-static struct dentry *__d_obtain_alias(struct inode *inode, int disconnected)
+static struct dentry *__d_instantiate_anon(struct dentry *dentry,
+					   struct inode *inode,
+					   bool disconnected)
 {
-	struct dentry *tmp;
 	struct dentry *res;
 	unsigned add_flags;
 
-	if (!inode)
-		return ERR_PTR(-ESTALE);
-	if (IS_ERR(inode))
-		return ERR_CAST(inode);
-
-	res = d_find_any_alias(inode);
-	if (res)
-		goto out_iput;
-
-	tmp = __d_alloc(inode->i_sb, NULL);
-	if (!tmp) {
-		res = ERR_PTR(-ENOMEM);
-		goto out_iput;
-	}
-
-	security_d_instantiate(tmp, inode);
+	security_d_instantiate(dentry, inode);
 	spin_lock(&inode->i_lock);
 	res = __d_find_any_alias(inode);
 	if (res) {
 		spin_unlock(&inode->i_lock);
-		dput(tmp);
+		dput(dentry);
 		goto out_iput;
 	}
 
@@ -1961,24 +1953,57 @@ static struct dentry *__d_obtain_alias(struct inode *inode, int disconnected)
 	if (disconnected)
 		add_flags |= DCACHE_DISCONNECTED;
 
-	spin_lock(&tmp->d_lock);
-	__d_set_inode_and_type(tmp, inode, add_flags);
-	hlist_add_head(&tmp->d_u.d_alias, &inode->i_dentry);
+	spin_lock(&dentry->d_lock);
+	__d_set_inode_and_type(dentry, inode, add_flags);
+	hlist_add_head(&dentry->d_u.d_alias, &inode->i_dentry);
 	if (!disconnected) {
-		hlist_bl_lock(&tmp->d_sb->s_roots);
-		hlist_bl_add_head(&tmp->d_hash, &tmp->d_sb->s_roots);
-		hlist_bl_unlock(&tmp->d_sb->s_roots);
+		hlist_bl_lock(&dentry->d_sb->s_roots);
+		hlist_bl_add_head(&dentry->d_hash, &dentry->d_sb->s_roots);
+		hlist_bl_unlock(&dentry->d_sb->s_roots);
 	}
-	spin_unlock(&tmp->d_lock);
+	spin_unlock(&dentry->d_lock);
 	spin_unlock(&inode->i_lock);
 
-	return tmp;
+	return dentry;
 
  out_iput:
 	iput(inode);
 	return res;
 }
 
+struct dentry *d_instantiate_anon(struct dentry *dentry, struct inode *inode)
+{
+	return __d_instantiate_anon(dentry, inode, true);
+}
+EXPORT_SYMBOL(d_instantiate_anon);
+
+static struct dentry *__d_obtain_alias(struct inode *inode, bool disconnected)
+{
+	struct dentry *tmp;
+	struct dentry *res;
+
+	if (!inode)
+		return ERR_PTR(-ESTALE);
+	if (IS_ERR(inode))
+		return ERR_CAST(inode);
+
+	res = d_find_any_alias(inode);
+	if (res)
+		goto out_iput;
+
+	tmp = d_alloc_anon(inode->i_sb);
+	if (!tmp) {
+		res = ERR_PTR(-ENOMEM);
+		goto out_iput;
+	}
+
+	return __d_instantiate_anon(tmp, inode, disconnected);
+
+out_iput:
+	iput(inode);
+	return res;
+}
+
 /**
  * d_obtain_alias - find or allocate a DISCONNECTED dentry for a given inode
  * @inode: inode to allocate the dentry for
@@ -1999,7 +2024,7 @@ static struct dentry *__d_obtain_alias(struct inode *inode, int disconnected)
  */
 struct dentry *d_obtain_alias(struct inode *inode)
 {
-	return __d_obtain_alias(inode, 1);
+	return __d_obtain_alias(inode, true);
 }
 EXPORT_SYMBOL(d_obtain_alias);
 
@@ -2020,7 +2045,7 @@ EXPORT_SYMBOL(d_obtain_alias);
  */
 struct dentry *d_obtain_root(struct inode *inode)
 {
-	return __d_obtain_alias(inode, 0);
+	return __d_obtain_alias(inode, false);
 }
 EXPORT_SYMBOL(d_obtain_root);
 
@@ -3527,6 +3552,7 @@ bool is_subdir(struct dentry *new_dentry, struct dentry *old_dentry)
 
 	return result;
 }
+EXPORT_SYMBOL(is_subdir);
 
 static enum d_walk_ret d_genocide_kill(void *data, struct dentry *dentry)
 {
diff --git a/fs/overlayfs/Kconfig b/fs/overlayfs/Kconfig
index 5ac415466861..406e72de88f6 100644
--- a/fs/overlayfs/Kconfig
+++ b/fs/overlayfs/Kconfig
@@ -47,9 +47,28 @@ config OVERLAY_FS_INDEX
 	  The inodes index feature prevents breaking of lower hardlinks on copy
 	  up.
 
-	  Note, that the inodes index feature is read-only backward compatible.
-	  That is, mounting an overlay which has an index dir on a kernel that
-	  doesn't support this feature read-only, will not have any negative
-	  outcomes.  However, mounting the same overlay with an old kernel
-	  read-write and then mounting it again with a new kernel, will have
-	  unexpected results.
+	  Note, that the inodes index feature is not backward compatible.
+	  That is, mounting an overlay which has an inodes index on a kernel
+	  that doesn't support this feature will have unexpected results.
+
+config OVERLAY_FS_NFS_EXPORT
+	bool "Overlayfs: turn on NFS export feature by default"
+	depends on OVERLAY_FS
+	depends on OVERLAY_FS_INDEX
+	help
+	  If this config option is enabled then overlay filesystems will use
+	  the inodes index dir to decode overlay NFS file handles by default.
+	  In this case, it is still possible to turn off NFS export support
+	  globally with the "nfs_export=off" module option or on a filesystem
+	  instance basis with the "nfs_export=off" mount option.
+
+	  The NFS export feature creates an index on copy up of every file and
+	  directory.  This full index is used to detect overlay filesystems
+	  inconsistencies on lookup, like redirect from multiple upper dirs to
+	  the same lower dir.  The full index may incur some overhead on mount
+	  time, especially when verifying that directory file handles are not
+	  stale.
+
+	  Note, that the NFS export feature is not backward compatible.
+	  That is, mounting an overlay which has a full index on a kernel
+	  that doesn't support this feature will have unexpected results.
diff --git a/fs/overlayfs/Makefile b/fs/overlayfs/Makefile
index 99373bbc1478..30802347a020 100644
--- a/fs/overlayfs/Makefile
+++ b/fs/overlayfs/Makefile
@@ -4,4 +4,5 @@
 
 obj-$(CONFIG_OVERLAY_FS) += overlay.o
 
-overlay-objs := super.o namei.o util.o inode.o dir.o readdir.o copy_up.o
+overlay-objs := super.o namei.o util.o inode.o dir.o readdir.o copy_up.o \
+		export.o
diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
index eb3b8d39fb61..d855f508fa20 100644
--- a/fs/overlayfs/copy_up.c
+++ b/fs/overlayfs/copy_up.c
@@ -232,13 +232,13 @@ int ovl_set_attr(struct dentry *upperdentry, struct kstat *stat)
 	return err;
 }
 
-struct ovl_fh *ovl_encode_fh(struct dentry *lower, bool is_upper)
+struct ovl_fh *ovl_encode_fh(struct dentry *real, bool is_upper)
 {
 	struct ovl_fh *fh;
 	int fh_type, fh_len, dwords;
 	void *buf;
 	int buflen = MAX_HANDLE_SZ;
-	uuid_t *uuid = &lower->d_sb->s_uuid;
+	uuid_t *uuid = &real->d_sb->s_uuid;
 
 	buf = kmalloc(buflen, GFP_KERNEL);
 	if (!buf)
@@ -250,7 +250,7 @@ struct ovl_fh *ovl_encode_fh(struct dentry *lower, bool is_upper)
 	 * the price or reconnecting the dentry.
 	 */
 	dwords = buflen >> 2;
-	fh_type = exportfs_encode_fh(lower, buf, &dwords, 0);
+	fh_type = exportfs_encode_fh(real, buf, &dwords, 0);
 	buflen = (dwords << 2);
 
 	fh = ERR_PTR(-EIO);
@@ -288,8 +288,8 @@ out:
 	return fh;
 }
 
-static int ovl_set_origin(struct dentry *dentry, struct dentry *lower,
-			  struct dentry *upper)
+int ovl_set_origin(struct dentry *dentry, struct dentry *lower,
+		   struct dentry *upper)
 {
 	const struct ovl_fh *fh = NULL;
 	int err;
@@ -315,6 +315,94 @@ static int ovl_set_origin(struct dentry *dentry, struct dentry *lower,
 	return err;
 }
 
+/* Store file handle of @upper dir in @index dir entry */
+static int ovl_set_upper_fh(struct dentry *upper, struct dentry *index)
+{
+	const struct ovl_fh *fh;
+	int err;
+
+	fh = ovl_encode_fh(upper, true);
+	if (IS_ERR(fh))
+		return PTR_ERR(fh);
+
+	err = ovl_do_setxattr(index, OVL_XATTR_UPPER, fh, fh->len, 0);
+
+	kfree(fh);
+	return err;
+}
+
+/*
+ * Create and install index entry.
+ *
+ * Caller must hold i_mutex on indexdir.
+ */
+static int ovl_create_index(struct dentry *dentry, struct dentry *origin,
+			    struct dentry *upper)
+{
+	struct dentry *indexdir = ovl_indexdir(dentry->d_sb);
+	struct inode *dir = d_inode(indexdir);
+	struct dentry *index = NULL;
+	struct dentry *temp = NULL;
+	struct qstr name = { };
+	int err;
+
+	/*
+	 * For now this is only used for creating index entry for directories,
+	 * because non-dir are copied up directly to index and then hardlinked
+	 * to upper dir.
+	 *
+	 * TODO: implement create index for non-dir, so we can call it when
+	 * encoding file handle for non-dir in case index does not exist.
+	 */
+	if (WARN_ON(!d_is_dir(dentry)))
+		return -EIO;
+
+	/* Directory not expected to be indexed before copy up */
+	if (WARN_ON(ovl_test_flag(OVL_INDEX, d_inode(dentry))))
+		return -EIO;
+
+	err = ovl_get_index_name(origin, &name);
+	if (err)
+		return err;
+
+	temp = ovl_lookup_temp(indexdir);
+	if (IS_ERR(temp))
+		goto temp_err;
+
+	err = ovl_do_mkdir(dir, temp, S_IFDIR, true);
+	if (err)
+		goto out;
+
+	err = ovl_set_upper_fh(upper, temp);
+	if (err)
+		goto out_cleanup;
+
+	index = lookup_one_len(name.name, indexdir, name.len);
+	if (IS_ERR(index)) {
+		err = PTR_ERR(index);
+	} else {
+		err = ovl_do_rename(dir, temp, dir, index, 0);
+		dput(index);
+	}
+
+	if (err)
+		goto out_cleanup;
+
+out:
+	dput(temp);
+	kfree(name.name);
+	return err;
+
+temp_err:
+	err = PTR_ERR(temp);
+	temp = NULL;
+	goto out;
+
+out_cleanup:
+	ovl_cleanup(dir, temp);
+	goto out;
+}
+
 struct ovl_copy_up_ctx {
 	struct dentry *parent;
 	struct dentry *dentry;
@@ -327,6 +415,7 @@ struct ovl_copy_up_ctx {
 	struct dentry *workdir;
 	bool tmpfile;
 	bool origin;
+	bool indexed;
 };
 
 static int ovl_link_up(struct ovl_copy_up_ctx *c)
@@ -361,7 +450,10 @@ static int ovl_link_up(struct ovl_copy_up_ctx *c)
 		}
 	}
 	inode_unlock(udir);
-	ovl_set_nlink_upper(c->dentry);
+	if (err)
+		return err;
+
+	err = ovl_set_nlink_upper(c->dentry);
 
 	return err;
 }
@@ -498,6 +590,12 @@ static int ovl_copy_up_locked(struct ovl_copy_up_ctx *c)
 	if (err)
 		goto out_cleanup;
 
+	if (S_ISDIR(c->stat.mode) && c->indexed) {
+		err = ovl_create_index(c->dentry, c->lowerpath.dentry, temp);
+		if (err)
+			goto out_cleanup;
+	}
+
 	if (c->tmpfile) {
 		inode_lock_nested(udir, I_MUTEX_PARENT);
 		err = ovl_install_temp(c, temp, &newdentry);
@@ -536,20 +634,33 @@ static int ovl_do_copy_up(struct ovl_copy_up_ctx *c)
 {
 	int err;
 	struct ovl_fs *ofs = c->dentry->d_sb->s_fs_info;
-	bool indexed = false;
+	bool to_index = false;
 
-	if (ovl_indexdir(c->dentry->d_sb) && !S_ISDIR(c->stat.mode) &&
-	    c->stat.nlink > 1)
-		indexed = true;
+	/*
+	 * Indexed non-dir is copied up directly to the index entry and then
+	 * hardlinked to upper dir. Indexed dir is copied up to indexdir,
+	 * then index entry is created and then copied up dir installed.
+	 * Copying dir up to indexdir instead of workdir simplifies locking.
+	 */
+	if (ovl_need_index(c->dentry)) {
+		c->indexed = true;
+		if (S_ISDIR(c->stat.mode))
+			c->workdir = ovl_indexdir(c->dentry->d_sb);
+		else
+			to_index = true;
+	}
 
-	if (S_ISDIR(c->stat.mode) || c->stat.nlink == 1 || indexed)
+	if (S_ISDIR(c->stat.mode) || c->stat.nlink == 1 || to_index)
 		c->origin = true;
 
-	if (indexed) {
+	if (to_index) {
 		c->destdir = ovl_indexdir(c->dentry->d_sb);
 		err = ovl_get_index_name(c->lowerpath.dentry, &c->destname);
 		if (err)
 			return err;
+	} else if (WARN_ON(!c->parent)) {
+		/* Disconnected dentry must be copied up to index dir */
+		return -EIO;
 	} else {
 		/*
 		 * Mark parent "impure" because it may now contain non-pure
@@ -572,11 +683,17 @@ static int ovl_do_copy_up(struct ovl_copy_up_ctx *c)
 		}
 	}
 
-	if (indexed) {
-		if (!err)
-			ovl_set_flag(OVL_INDEX, d_inode(c->dentry));
-		kfree(c->destname.name);
-	} else if (!err) {
+
+	if (err)
+		goto out;
+
+	if (c->indexed)
+		ovl_set_flag(OVL_INDEX, d_inode(c->dentry));
+
+	if (to_index) {
+		/* Initialize nlink for copy up of disconnected dentry */
+		err = ovl_set_nlink_upper(c->dentry);
+	} else {
 		struct inode *udir = d_inode(c->destdir);
 
 		/* Restore timestamps on parent (best effort) */
@@ -587,6 +704,9 @@ static int ovl_do_copy_up(struct ovl_copy_up_ctx *c)
 		ovl_dentry_set_upper_alias(c->dentry);
 	}
 
+out:
+	if (to_index)
+		kfree(c->destname.name);
 	return err;
 }
 
@@ -611,14 +731,17 @@ static int ovl_copy_up_one(struct dentry *parent, struct dentry *dentry,
 	if (err)
 		return err;
 
-	ovl_path_upper(parent, &parentpath);
-	ctx.destdir = parentpath.dentry;
-	ctx.destname = dentry->d_name;
+	if (parent) {
+		ovl_path_upper(parent, &parentpath);
+		ctx.destdir = parentpath.dentry;
+		ctx.destname = dentry->d_name;
 
-	err = vfs_getattr(&parentpath, &ctx.pstat,
-			  STATX_ATIME | STATX_MTIME, AT_STATX_SYNC_AS_STAT);
-	if (err)
-		return err;
+		err = vfs_getattr(&parentpath, &ctx.pstat,
+				  STATX_ATIME | STATX_MTIME,
+				  AT_STATX_SYNC_AS_STAT);
+		if (err)
+			return err;
+	}
 
 	/* maybe truncate regular file. this has no effect on dirs */
 	if (flags & O_TRUNC)
@@ -639,7 +762,7 @@ static int ovl_copy_up_one(struct dentry *parent, struct dentry *dentry,
 	} else {
 		if (!ovl_dentry_upper(dentry))
 			err = ovl_do_copy_up(&ctx);
-		if (!err && !ovl_dentry_has_upper_alias(dentry))
+		if (!err && parent && !ovl_dentry_has_upper_alias(dentry))
 			err = ovl_link_up(&ctx);
 		ovl_copy_up_end(dentry);
 	}
@@ -652,10 +775,19 @@ int ovl_copy_up_flags(struct dentry *dentry, int flags)
 {
 	int err = 0;
 	const struct cred *old_cred = ovl_override_creds(dentry->d_sb);
+	bool disconnected = (dentry->d_flags & DCACHE_DISCONNECTED);
+
+	/*
+	 * With NFS export, copy up can get called for a disconnected non-dir.
+	 * In this case, we will copy up lower inode to index dir without
+	 * linking it to upper dir.
+	 */
+	if (WARN_ON(disconnected && d_is_dir(dentry)))
+		return -EIO;
 
 	while (!err) {
 		struct dentry *next;
-		struct dentry *parent;
+		struct dentry *parent = NULL;
 
 		/*
 		 * Check if copy-up has happened as well as for upper alias (in
@@ -671,12 +803,12 @@ int ovl_copy_up_flags(struct dentry *dentry, int flags)
 		 *      with rename.
 		 */
 		if (ovl_dentry_upper(dentry) &&
-		    ovl_dentry_has_upper_alias(dentry))
+		    (ovl_dentry_has_upper_alias(dentry) || disconnected))
 			break;
 
 		next = dget(dentry);
 		/* find the topmost dentry not yet copied up */
-		for (;;) {
+		for (; !disconnected;) {
 			parent = dget_parent(next);
 
 			if (ovl_dentry_upper(parent))
diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index f9788bc116a8..839709c7803a 100644
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -63,8 +63,7 @@ struct dentry *ovl_lookup_temp(struct dentry *workdir)
 }
 
 /* caller holds i_mutex on workdir */
-static struct dentry *ovl_whiteout(struct dentry *workdir,
-				   struct dentry *dentry)
+static struct dentry *ovl_whiteout(struct dentry *workdir)
 {
 	int err;
 	struct dentry *whiteout;
@@ -83,6 +82,38 @@ static struct dentry *ovl_whiteout(struct dentry *workdir,
 	return whiteout;
 }
 
+/* Caller must hold i_mutex on both workdir and dir */
+int ovl_cleanup_and_whiteout(struct dentry *workdir, struct inode *dir,
+			     struct dentry *dentry)
+{
+	struct inode *wdir = workdir->d_inode;
+	struct dentry *whiteout;
+	int err;
+	int flags = 0;
+
+	whiteout = ovl_whiteout(workdir);
+	err = PTR_ERR(whiteout);
+	if (IS_ERR(whiteout))
+		return err;
+
+	if (d_is_dir(dentry))
+		flags = RENAME_EXCHANGE;
+
+	err = ovl_do_rename(wdir, whiteout, dir, dentry, flags);
+	if (err)
+		goto kill_whiteout;
+	if (flags)
+		ovl_cleanup(wdir, dentry);
+
+out:
+	dput(whiteout);
+	return err;
+
+kill_whiteout:
+	ovl_cleanup(wdir, whiteout);
+	goto out;
+}
+
 int ovl_create_real(struct inode *dir, struct dentry *newdentry,
 		    struct cattr *attr, struct dentry *hardlink, bool debug)
 {
@@ -181,11 +212,6 @@ static bool ovl_type_origin(struct dentry *dentry)
 	return OVL_TYPE_ORIGIN(ovl_path_type(dentry));
 }
 
-static bool ovl_may_have_whiteouts(struct dentry *dentry)
-{
-	return ovl_test_flag(OVL_WHITEOUTS, d_inode(dentry));
-}
-
 static int ovl_create_upper(struct dentry *dentry, struct inode *inode,
 			    struct cattr *attr, struct dentry *hardlink)
 {
@@ -301,37 +327,6 @@ out:
 	return ERR_PTR(err);
 }
 
-static struct dentry *ovl_check_empty_and_clear(struct dentry *dentry)
-{
-	int err;
-	struct dentry *ret = NULL;
-	LIST_HEAD(list);
-
-	err = ovl_check_empty_dir(dentry, &list);
-	if (err) {
-		ret = ERR_PTR(err);
-		goto out_free;
-	}
-
-	/*
-	 * When removing an empty opaque directory, then it makes no sense to
-	 * replace it with an exact replica of itself.
-	 *
-	 * If upperdentry has whiteouts, clear them.
-	 *
-	 * Can race with copy-up, since we don't hold the upperdir mutex.
-	 * Doesn't matter, since copy-up can't create a non-empty directory
-	 * from an empty one.
-	 */
-	if (!list_empty(&list))
-		ret = ovl_clear_empty(dentry, &list);
-
-out_free:
-	ovl_cache_free(&list);
-
-	return ret;
-}
-
 static int ovl_set_upper_acl(struct dentry *upperdentry, const char *name,
 			     const struct posix_acl *acl)
 {
@@ -623,23 +618,20 @@ static bool ovl_matches_upper(struct dentry *dentry, struct dentry *upper)
 	return d_inode(ovl_dentry_upper(dentry)) == d_inode(upper);
 }
 
-static int ovl_remove_and_whiteout(struct dentry *dentry, bool is_dir)
+static int ovl_remove_and_whiteout(struct dentry *dentry,
+				   struct list_head *list)
 {
 	struct dentry *workdir = ovl_workdir(dentry);
-	struct inode *wdir = workdir->d_inode;
 	struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
-	struct inode *udir = upperdir->d_inode;
-	struct dentry *whiteout;
 	struct dentry *upper;
 	struct dentry *opaquedir = NULL;
 	int err;
-	int flags = 0;
 
 	if (WARN_ON(!workdir))
 		return -EROFS;
 
-	if (is_dir) {
-		opaquedir = ovl_check_empty_and_clear(dentry);
+	if (!list_empty(list)) {
+		opaquedir = ovl_clear_empty(dentry, list);
 		err = PTR_ERR(opaquedir);
 		if (IS_ERR(opaquedir))
 			goto out;
@@ -662,24 +654,13 @@ static int ovl_remove_and_whiteout(struct dentry *dentry, bool is_dir)
 		goto out_dput_upper;
 	}
 
-	whiteout = ovl_whiteout(workdir, dentry);
-	err = PTR_ERR(whiteout);
-	if (IS_ERR(whiteout))
-		goto out_dput_upper;
-
-	if (d_is_dir(upper))
-		flags = RENAME_EXCHANGE;
-
-	err = ovl_do_rename(wdir, whiteout, udir, upper, flags);
+	err = ovl_cleanup_and_whiteout(workdir, d_inode(upperdir), upper);
 	if (err)
-		goto kill_whiteout;
-	if (flags)
-		ovl_cleanup(wdir, upper);
+		goto out_d_drop;
 
 	ovl_dentry_version_inc(dentry->d_parent, true);
 out_d_drop:
 	d_drop(dentry);
-	dput(whiteout);
 out_dput_upper:
 	dput(upper);
 out_unlock:
@@ -688,13 +669,10 @@ out_dput:
 	dput(opaquedir);
 out:
 	return err;
-
-kill_whiteout:
-	ovl_cleanup(wdir, whiteout);
-	goto out_d_drop;
 }
 
-static int ovl_remove_upper(struct dentry *dentry, bool is_dir)
+static int ovl_remove_upper(struct dentry *dentry, bool is_dir,
+			    struct list_head *list)
 {
 	struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
 	struct inode *dir = upperdir->d_inode;
@@ -702,10 +680,8 @@ static int ovl_remove_upper(struct dentry *dentry, bool is_dir)
 	struct dentry *opaquedir = NULL;
 	int err;
 
-	/* Redirect/origin dir can be !ovl_lower_positive && not clean */
-	if (is_dir && (ovl_dentry_get_redirect(dentry) ||
-		       ovl_may_have_whiteouts(dentry))) {
-		opaquedir = ovl_check_empty_and_clear(dentry);
+	if (!list_empty(list)) {
+		opaquedir = ovl_clear_empty(dentry, list);
 		err = PTR_ERR(opaquedir);
 		if (IS_ERR(opaquedir))
 			goto out;
@@ -746,11 +722,26 @@ out:
 	return err;
 }
 
+static bool ovl_pure_upper(struct dentry *dentry)
+{
+	return !ovl_dentry_lower(dentry) &&
+	       !ovl_test_flag(OVL_WHITEOUTS, d_inode(dentry));
+}
+
 static int ovl_do_remove(struct dentry *dentry, bool is_dir)
 {
 	int err;
 	bool locked = false;
 	const struct cred *old_cred;
+	bool lower_positive = ovl_lower_positive(dentry);
+	LIST_HEAD(list);
+
+	/* No need to clean pure upper removed by vfs_rmdir() */
+	if (is_dir && (lower_positive || !ovl_pure_upper(dentry))) {
+		err = ovl_check_empty_dir(dentry, &list);
+		if (err)
+			goto out;
+	}
 
 	err = ovl_want_write(dentry);
 	if (err)
@@ -765,10 +756,10 @@ static int ovl_do_remove(struct dentry *dentry, bool is_dir)
 		goto out_drop_write;
 
 	old_cred = ovl_override_creds(dentry->d_sb);
-	if (!ovl_lower_positive(dentry))
-		err = ovl_remove_upper(dentry, is_dir);
+	if (!lower_positive)
+		err = ovl_remove_upper(dentry, is_dir, &list);
 	else
-		err = ovl_remove_and_whiteout(dentry, is_dir);
+		err = ovl_remove_and_whiteout(dentry, &list);
 	revert_creds(old_cred);
 	if (!err) {
 		if (is_dir)
@@ -780,6 +771,7 @@ static int ovl_do_remove(struct dentry *dentry, bool is_dir)
 out_drop_write:
 	ovl_drop_write(dentry);
 out:
+	ovl_cache_free(&list);
 	return err;
 }
 
@@ -915,6 +907,7 @@ static int ovl_rename(struct inode *olddir, struct dentry *old,
 	bool samedir = olddir == newdir;
 	struct dentry *opaquedir = NULL;
 	const struct cred *old_cred = NULL;
+	LIST_HEAD(list);
 
 	err = -EINVAL;
 	if (flags & ~(RENAME_EXCHANGE | RENAME_NOREPLACE))
@@ -929,6 +922,27 @@ static int ovl_rename(struct inode *olddir, struct dentry *old,
 	if (!overwrite && !ovl_can_move(new))
 		goto out;
 
+	if (overwrite && new_is_dir && !ovl_pure_upper(new)) {
+		err = ovl_check_empty_dir(new, &list);
+		if (err)
+			goto out;
+	}
+
+	if (overwrite) {
+		if (ovl_lower_positive(old)) {
+			if (!ovl_dentry_is_whiteout(new)) {
+				/* Whiteout source */
+				flags |= RENAME_WHITEOUT;
+			} else {
+				/* Switch whiteouts */
+				flags |= RENAME_EXCHANGE;
+			}
+		} else if (is_dir && ovl_dentry_is_whiteout(new)) {
+			flags |= RENAME_EXCHANGE;
+			cleanup_whiteout = true;
+		}
+	}
+
 	err = ovl_want_write(old);
 	if (err)
 		goto out;
@@ -952,9 +966,8 @@ static int ovl_rename(struct inode *olddir, struct dentry *old,
 
 	old_cred = ovl_override_creds(old->d_sb);
 
-	if (overwrite && new_is_dir && (ovl_type_merge_or_lower(new) ||
-					ovl_may_have_whiteouts(new))) {
-		opaquedir = ovl_check_empty_and_clear(new);
+	if (!list_empty(&list)) {
+		opaquedir = ovl_clear_empty(new, &list);
 		err = PTR_ERR(opaquedir);
 		if (IS_ERR(opaquedir)) {
 			opaquedir = NULL;
@@ -962,21 +975,6 @@ static int ovl_rename(struct inode *olddir, struct dentry *old,
 		}
 	}
 
-	if (overwrite) {
-		if (ovl_lower_positive(old)) {
-			if (!ovl_dentry_is_whiteout(new)) {
-				/* Whiteout source */
-				flags |= RENAME_WHITEOUT;
-			} else {
-				/* Switch whiteouts */
-				flags |= RENAME_EXCHANGE;
-			}
-		} else if (is_dir && ovl_dentry_is_whiteout(new)) {
-			flags |= RENAME_EXCHANGE;
-			cleanup_whiteout = true;
-		}
-	}
-
 	old_upperdir = ovl_dentry_upper(old->d_parent);
 	new_upperdir = ovl_dentry_upper(new->d_parent);
 
@@ -1094,6 +1092,7 @@ out_drop_write:
 	ovl_drop_write(old);
 out:
 	dput(opaquedir);
+	ovl_cache_free(&list);
 	return err;
 }
 
diff --git a/fs/overlayfs/export.c b/fs/overlayfs/export.c
new file mode 100644
index 000000000000..bb94ce9da5c8
--- /dev/null
+++ b/fs/overlayfs/export.c
@@ -0,0 +1,715 @@
+/*
+ * Overlayfs NFS export support.
+ *
+ * Amir Goldstein <amir73il@gmail.com>
+ *
+ * Copyright (C) 2017-2018 CTERA Networks. All Rights Reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published by
+ * the Free Software Foundation.
+ */
+
+#include <linux/fs.h>
+#include <linux/cred.h>
+#include <linux/mount.h>
+#include <linux/namei.h>
+#include <linux/xattr.h>
+#include <linux/exportfs.h>
+#include <linux/ratelimit.h>
+#include "overlayfs.h"
+
+/*
+ * We only need to encode origin if there is a chance that the same object was
+ * encoded pre copy up and then we need to stay consistent with the same
+ * encoding also after copy up. If non-pure upper is not indexed, then it was
+ * copied up before NFS export was enabled. In that case we don't need to worry
+ * about staying consistent with pre copy up encoding and we encode an upper
+ * file handle. Overlay root dentry is a private case of non-indexed upper.
+ *
+ * The following table summarizes the different file handle encodings used for
+ * different overlay object types:
+ *
+ *  Object type		| Encoding
+ * --------------------------------
+ *  Pure upper		| U
+ *  Non-indexed upper	| U
+ *  Indexed upper	| L (*)
+ *  Non-upper		| L (*)
+ *
+ * U = upper file handle
+ * L = lower file handle
+ *
+ * (*) Connecting an overlay dir from real lower dentry is not always
+ * possible when there are redirects in lower layers. To mitigate this case,
+ * we copy up the lower dir first and then encode an upper dir file handle.
+ */
+static bool ovl_should_encode_origin(struct dentry *dentry)
+{
+	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
+
+	if (!ovl_dentry_lower(dentry))
+		return false;
+
+	/*
+	 * Decoding a merge dir, whose origin's parent is under a redirected
+	 * lower dir is not always possible. As a simple aproximation, we do
+	 * not encode lower dir file handles when overlay has multiple lower
+	 * layers and origin is below the topmost lower layer.
+	 *
+	 * TODO: copy up only the parent that is under redirected lower.
+	 */
+	if (d_is_dir(dentry) && ofs->upper_mnt &&
+	    OVL_E(dentry)->lowerstack[0].layer->idx > 1)
+		return false;
+
+	/* Decoding a non-indexed upper from origin is not implemented */
+	if (ovl_dentry_upper(dentry) &&
+	    !ovl_test_flag(OVL_INDEX, d_inode(dentry)))
+		return false;
+
+	return true;
+}
+
+static int ovl_encode_maybe_copy_up(struct dentry *dentry)
+{
+	int err;
+
+	if (ovl_dentry_upper(dentry))
+		return 0;
+
+	err = ovl_want_write(dentry);
+	if (err)
+		return err;
+
+	err = ovl_copy_up(dentry);
+
+	ovl_drop_write(dentry);
+	return err;
+}
+
+static int ovl_d_to_fh(struct dentry *dentry, char *buf, int buflen)
+{
+	struct dentry *origin = ovl_dentry_lower(dentry);
+	struct ovl_fh *fh = NULL;
+	int err;
+
+	/*
+	 * If we should not encode a lower dir file handle, copy up and encode
+	 * an upper dir file handle.
+	 */
+	if (!ovl_should_encode_origin(dentry)) {
+		err = ovl_encode_maybe_copy_up(dentry);
+		if (err)
+			goto fail;
+
+		origin = NULL;
+	}
+
+	/* Encode an upper or origin file handle */
+	fh = ovl_encode_fh(origin ?: ovl_dentry_upper(dentry), !origin);
+	err = PTR_ERR(fh);
+	if (IS_ERR(fh))
+		goto fail;
+
+	err = -EOVERFLOW;
+	if (fh->len > buflen)
+		goto fail;
+
+	memcpy(buf, (char *)fh, fh->len);
+	err = fh->len;
+
+out:
+	kfree(fh);
+	return err;
+
+fail:
+	pr_warn_ratelimited("overlayfs: failed to encode file handle (%pd2, err=%i, buflen=%d, len=%d, type=%d)\n",
+			    dentry, err, buflen, fh ? (int)fh->len : 0,
+			    fh ? fh->type : 0);
+	goto out;
+}
+
+static int ovl_dentry_to_fh(struct dentry *dentry, u32 *fid, int *max_len)
+{
+	int res, len = *max_len << 2;
+
+	res = ovl_d_to_fh(dentry, (char *)fid, len);
+	if (res <= 0)
+		return FILEID_INVALID;
+
+	len = res;
+
+	/* Round up to dwords */
+	*max_len = (len + 3) >> 2;
+	return OVL_FILEID;
+}
+
+static int ovl_encode_inode_fh(struct inode *inode, u32 *fid, int *max_len,
+			       struct inode *parent)
+{
+	struct dentry *dentry;
+	int type;
+
+	/* TODO: encode connectable file handles */
+	if (parent)
+		return FILEID_INVALID;
+
+	dentry = d_find_any_alias(inode);
+	if (WARN_ON(!dentry))
+		return FILEID_INVALID;
+
+	type = ovl_dentry_to_fh(dentry, fid, max_len);
+
+	dput(dentry);
+	return type;
+}
+
+/*
+ * Find or instantiate an overlay dentry from real dentries and index.
+ */
+static struct dentry *ovl_obtain_alias(struct super_block *sb,
+				       struct dentry *upper_alias,
+				       struct ovl_path *lowerpath,
+				       struct dentry *index)
+{
+	struct dentry *lower = lowerpath ? lowerpath->dentry : NULL;
+	struct dentry *upper = upper_alias ?: index;
+	struct dentry *dentry;
+	struct inode *inode;
+	struct ovl_entry *oe;
+
+	/* We get overlay directory dentries with ovl_lookup_real() */
+	if (d_is_dir(upper ?: lower))
+		return ERR_PTR(-EIO);
+
+	inode = ovl_get_inode(sb, dget(upper), lower, index, !!lower);
+	if (IS_ERR(inode)) {
+		dput(upper);
+		return ERR_CAST(inode);
+	}
+
+	if (index)
+		ovl_set_flag(OVL_INDEX, inode);