aufs: inode op, del, rmdir

Implement i_op->rmdir() with supporting logical deletion by whiteout
including all children.

As struct.txt in previous commit described, the target dir is renamed to
a whiteout-ed temporary unique name in rmdir(2), and then removed
asynchronously by the system global workqueue.
Signed-off-by: J. R. Okajima <hooanon05g@gmail.com>

fs/aufs/dir.c

@@ -185,3 +185,210 @@ void au_dir_ts(struct inode *dir, aufs_bindex_t bindex)
 out:
 	dput(dentry);
 }
+
+/* ---------------------------------------------------------------------- */
+
+#define AuTestEmpty_WHONLY	1
+#define AuTestEmpty_CALLED	(1 << 1)
+#define au_ftest_testempty(flags, name)	((flags) & AuTestEmpty_##name)
+#define au_fset_testempty(flags, name) \
+	do { (flags) |= AuTestEmpty_##name; } while (0)
+#define au_fclr_testempty(flags, name) \
+	do { (flags) &= ~AuTestEmpty_##name; } while (0)
+
+struct test_empty_arg {
+	struct dir_context ctx;
+	struct au_nhash *whlist;
+	unsigned int flags;
+	int err;
+	aufs_bindex_t bindex;
+};
+
+static int test_empty_cb(struct dir_context *ctx, const char *__name,
+			 int namelen, loff_t offset __maybe_unused, u64 ino,
+			 unsigned int d_type)
+{
+	struct test_empty_arg *arg = container_of(ctx, struct test_empty_arg,
+						  ctx);
+	char *name = (void *)__name;
+
+	arg->err = 0;
+	au_fset_testempty(arg->flags, CALLED);
+	/* smp_mb(); */
+	if (name[0] == '.'
+	    && (namelen == 1 || (name[1] == '.' && namelen == 2)))
+		goto out; /* success */
+
+	if (namelen <= AUFS_WH_PFX_LEN
+	    || memcmp(name, AUFS_WH_PFX, AUFS_WH_PFX_LEN)) {
+		if (au_ftest_testempty(arg->flags, WHONLY)
+		    && !au_nhash_test_known_wh(arg->whlist, name, namelen))
+			arg->err = -ENOTEMPTY;
+		goto out;
+	}
+
+	name += AUFS_WH_PFX_LEN;
+	namelen -= AUFS_WH_PFX_LEN;
+	if (!au_nhash_test_known_wh(arg->whlist, name, namelen))
+		arg->err = au_nhash_append_wh
+			(arg->whlist, name, namelen, ino, d_type, arg->bindex);
+
+out:
+	/* smp_mb(); */
+	AuTraceErr(arg->err);
+	return arg->err;
+}
+
+static int do_test_empty(struct dentry *dentry, struct test_empty_arg *arg)
+{
+	int err;
+	struct file *h_file;
+	struct au_branch *br;
+
+	h_file = au_h_open(dentry, arg->bindex,
+			   O_RDONLY | O_NONBLOCK | O_DIRECTORY | O_LARGEFILE,
+			   /*file*/NULL);
+	err = PTR_ERR(h_file);
+	if (IS_ERR(h_file))
+		goto out;
+
+	err = 0;
+	if (!au_opt_test(au_mntflags(dentry->d_sb), UDBA_NONE)
+	    && !file_inode(h_file)->i_nlink)
+		goto out_put;
+
+	do {
+		arg->err = 0;
+		au_fclr_testempty(arg->flags, CALLED);
+		/* smp_mb(); */
+		err = vfsub_iterate_dir(h_file, &arg->ctx);
+		if (err >= 0)
+			err = arg->err;
+	} while (!err && au_ftest_testempty(arg->flags, CALLED));
+
+out_put:
+	fput(h_file);
+	br = au_sbr(dentry->d_sb, arg->bindex);
+	au_lcnt_dec(&br->br_nfiles);
+out:
+	return err;
+}
+
+struct do_test_empty_args {
+	int *errp;
+	struct dentry *dentry;
+	struct test_empty_arg *arg;
+};
+
+static void call_do_test_empty(void *args)
+{
+	struct do_test_empty_args *a = args;
+	*a->errp = do_test_empty(a->dentry, a->arg);
+}
+
+static int sio_test_empty(struct dentry *dentry, struct test_empty_arg *arg)
+{
+	int err, wkq_err;
+	struct dentry *h_dentry;
+	struct inode *h_inode;
+
+	h_dentry = au_h_dptr(dentry, arg->bindex);
+	h_inode = d_inode(h_dentry);
+	/* todo: i_mode changes anytime? */
+	inode_lock_shared_nested(h_inode, AuLsc_I_CHILD);
+	err = au_test_h_perm_sio(h_inode, MAY_EXEC | MAY_READ);
+	inode_unlock_shared(h_inode);
+	if (!err)
+		err = do_test_empty(dentry, arg);
+	else {
+		struct do_test_empty_args args = {
+			.errp	= &err,
+			.dentry	= dentry,
+			.arg	= arg
+		};
+		unsigned int flags = arg->flags;
+
+		wkq_err = au_wkq_wait(call_do_test_empty, &args);
+		if (unlikely(wkq_err))
+			err = wkq_err;
+		arg->flags = flags;
+	}
+
+	return err;
+}
+
+int au_test_empty_lower(struct dentry *dentry)
+{
+	int err;
+	unsigned int rdhash;
+	aufs_bindex_t bindex, btop, btail;
+	struct au_nhash whlist;
+	struct test_empty_arg arg = {
+		.ctx = {
+			.actor = test_empty_cb
+		}
+	};
+	int (*test_empty)(struct dentry *dentry, struct test_empty_arg *arg);
+
+	SiMustAnyLock(dentry->d_sb);
+
+	rdhash = au_sbi(dentry->d_sb)->si_rdhash;
+	if (!rdhash)
+		rdhash = au_rdhash_est(au_dir_size(/*file*/NULL, dentry));
+	err = au_nhash_alloc(&whlist, rdhash, GFP_NOFS);
+	if (unlikely(err))
+		goto out;
+
+	arg.flags = 0;
+	arg.whlist = &whlist;
+	btop = au_dbtop(dentry);
+	test_empty = do_test_empty;
+	arg.bindex = btop;
+	err = test_empty(dentry, &arg);
+	if (unlikely(err))
+		goto out_whlist;
+
+	au_fset_testempty(arg.flags, WHONLY);
+	btail = au_dbtaildir(dentry);
+	for (bindex = btop + 1; !err && bindex <= btail; bindex++) {
+		struct dentry *h_dentry;
+
+		h_dentry = au_h_dptr(dentry, bindex);
+		if (h_dentry && d_is_positive(h_dentry)) {
+			arg.bindex = bindex;
+			err = test_empty(dentry, &arg);
+		}
+	}
+
+out_whlist:
+	au_nhash_wh_free(&whlist);
+out:
+	return err;
+}
+
+int au_test_empty(struct dentry *dentry, struct au_nhash *whlist)
+{
+	int err;
+	struct test_empty_arg arg = {
+		.ctx = {
+			.actor = test_empty_cb
+		}
+	};
+	aufs_bindex_t bindex, btail;
+
+	err = 0;
+	arg.whlist = whlist;
+	arg.flags = AuTestEmpty_WHONLY;
+	btail = au_dbtaildir(dentry);
+	for (bindex = au_dbtop(dentry); !err && bindex <= btail; bindex++) {
+		struct dentry *h_dentry;
+
+		h_dentry = au_h_dptr(dentry, bindex);
+		if (h_dentry && d_is_positive(h_dentry)) {
+			arg.bindex = bindex;
+			err = sio_test_empty(dentry, &arg);
+		}
+	}
+
+	return err;
+}

fs/aufs/dir.h

@@ -74,6 +74,8 @@ void au_add_nlink(struct inode *dir, struct inode *h_dir);
 void au_sub_nlink(struct inode *dir, struct inode *h_dir);
 loff_t au_dir_size(struct file *file, struct dentry *dentry);
 void au_dir_ts(struct inode *dir, aufs_bindex_t bsrc);
+int au_test_empty_lower(struct dentry *dentry);
+int au_test_empty(struct dentry *dentry, struct au_nhash *whlist);
 
 /* vdir.c */
 unsigned int au_rdhash_est(loff_t sz);

fs/aufs/i_op.c

@@ -650,6 +650,7 @@ struct inode_operations aufs_iop[] = {
 		.unlink		= aufs_unlink,
 		.symlink	= aufs_symlink,
 		.mkdir		= aufs_mkdir,
+		.rmdir		= aufs_rmdir,
 		.mknod		= aufs_mknod,
 
 		.permission	= aufs_permission,

fs/aufs/i_op_del.c

@@ -192,6 +192,46 @@ out:
 	return wh_dentry;
 }
 
+/*
+ * when removing a dir, rename it to a unique temporary whiteout-ed name first
+ * in order to be revertible and save time for removing many child whiteouts
+ * under the dir.
+ * returns 1 when there are too many child whiteout and caller should remove
+ * them asynchronously. returns 0 when the number of children is enough small to
+ * remove now or the branch fs is a remote fs.
+ * otherwise return an error.
+ */
+static int renwh_and_rmdir(struct dentry *dentry, aufs_bindex_t bindex,
+			   struct au_nhash *whlist, struct inode *dir)
+{
+	int err;
+	struct dentry *h_dentry;
+	struct super_block *sb;
+	struct inode *inode;
+
+	sb = dentry->d_sb;
+	SiMustAnyLock(sb);
+	h_dentry = au_h_dptr(dentry, bindex);
+	err = au_whtmp_ren(h_dentry, au_sbr(sb, bindex));
+	if (unlikely(err))
+		goto out;
+
+	/* stop monitoring */
+	inode = d_inode(dentry);
+	au_hn_free(au_hi(inode, bindex));
+
+	err = au_whtmp_rmdir(dir, bindex, h_dentry, whlist);
+	if (unlikely(err)) {
+		AuIOErr("rmdir %pd, b%d failed, %d. ignored\n",
+			h_dentry, bindex, err);
+		err = 0;
+	}
+
+out:
+	AuTraceErr(err);
+	return err;
+}
+
 /*
  * final procedure for deleting a entry.
  * maintain dentry and iattr.
@@ -333,3 +373,114 @@ out_free:
 out:
 	return err;
 }
+
+int aufs_rmdir(struct inode *dir, struct dentry *dentry)
+{
+	int err, rmdir_later;
+	aufs_bindex_t bwh, bindex, btop;
+	struct inode *inode;
+	struct dentry *parent, *wh_dentry, *h_dentry;
+	struct au_whtmp_rmdir *args;
+	/* to reduce stack size */
+	struct {
+		struct au_dtime dt;
+		struct au_pin pin;
+	} *a;
+
+	IMustLock(dir);
+
+	err = -ENOMEM;
+	a = kmalloc(sizeof(*a), GFP_NOFS);
+	if (unlikely(!a))
+		goto out;
+
+	err = aufs_read_lock(dentry, AuLock_DW | AuLock_FLUSH | AuLock_GEN);
+	if (unlikely(err))
+		goto out_free;
+	err = au_alive_dir(dentry);
+	if (unlikely(err))
+		goto out_unlock;
+	inode = d_inode(dentry);
+	IMustLock(inode);
+	err = -ENOTDIR;
+	if (unlikely(!d_is_dir(dentry)))
+		goto out_unlock; /* possible? */
+
+	err = -ENOMEM;
+	args = au_whtmp_rmdir_alloc(dir->i_sb, GFP_NOFS);
+	if (unlikely(!args))
+		goto out_unlock;
+
+	parent = dentry->d_parent; /* dir inode is locked */
+	di_write_lock_parent(parent);
+	err = au_test_empty(dentry, &args->whlist);
+	if (unlikely(err))
+		goto out_parent;
+
+	btop = au_dbtop(dentry);
+	bwh = au_dbwh(dentry);
+	bindex = -1;
+	wh_dentry = lock_hdir_create_wh(dentry, /*isdir*/1, &bindex, &a->dt,
+					&a->pin);
+	err = PTR_ERR(wh_dentry);
+	if (IS_ERR(wh_dentry))
+		goto out_parent;
+
+	h_dentry = au_h_dptr(dentry, btop);
+	dget(h_dentry);
+	rmdir_later = 0;
+	if (bindex == btop) {
+		err = renwh_and_rmdir(dentry, btop, &args->whlist, dir);
+		if (err > 0) {
+			rmdir_later = err;
+			err = 0;
+		}
+	} else {
+		/* stop monitoring */
+		au_hn_free(au_hi(inode, btop));
+
+		/* dir inode is locked */
+		IMustLock(d_inode(wh_dentry->d_parent));
+		err = 0;
+	}
+
+	if (!err) {
+		vfsub_dead_dir(inode);
+		au_set_dbdiropq(dentry, -1);
+		epilog(dir, dentry, bindex);
+
+		if (rmdir_later) {
+			au_whtmp_kick_rmdir(dir, btop, h_dentry, args);
+			args = NULL;
+		}
+
+		goto out_unpin; /* success */
+	}
+
+	/* revert */
+	AuLabel(revert);
+	if (wh_dentry) {
+		int rerr;
+
+		rerr = do_revert(err, dir, bindex, bwh, wh_dentry, dentry,
+				 &a->dt);
+		if (rerr)
+			err = rerr;
+	}
+
+out_unpin:
+	au_unpin(&a->pin);
+	dput(wh_dentry);
+	dput(h_dentry);
+out_parent:
+	di_write_unlock(parent);
+	if (args)
+		au_whtmp_rmdir_free(args);
+out_unlock:
+	aufs_read_unlock(dentry, AuLock_DW);
+out_free:
+	au_kfree_rcu(a);
+out:
+	AuTraceErr(err);
+	return err;
+}

fs/aufs/inode.h

@@ -177,6 +177,7 @@ int au_wr_dir_need_wh(struct dentry *dentry, int isdir, aufs_bindex_t *bcpup);
 int au_may_del(struct dentry *dentry, aufs_bindex_t bindex,
 	       struct dentry *h_parent, int isdir);
 int aufs_unlink(struct inode *dir, struct dentry *dentry);
+int aufs_rmdir(struct inode *dir, struct dentry *dentry);
 
 /* iinfo.c */
 struct inode *au_h_iptr(struct inode *inode, aufs_bindex_t bindex);

fs/aufs/vfsub.h

@@ -43,6 +43,13 @@ static inline void vfsub_drop_nlink(struct inode *inode)
 	drop_nlink(inode);
 }
 
+static inline void vfsub_dead_dir(struct inode *inode)
+{
+	AuDebugOn(!S_ISDIR(inode->i_mode));
+	inode->i_flags |= S_DEAD;
+	clear_nlink(inode);
+}
+
 int vfsub_sync_filesystem(struct super_block *h_sb, int wait);
 
 /* ---------------------------------------------------------------------- */

fs/aufs/whout.c

@@ -156,6 +156,44 @@ out:
 	return dentry;
 }
 
+/*
+ * rename the @h_dentry on @br to the whiteouted temporary name.
+ */
+int au_whtmp_ren(struct dentry *h_dentry, struct au_branch *br)
+{
+	int err;
+	struct path h_path = {
+		.mnt = au_br_mnt(br)
+	};
+	struct inode *h_dir, *delegated;
+	struct dentry *h_parent;
+
+	h_parent = h_dentry->d_parent; /* dir inode is locked */
+	h_dir = d_inode(h_parent);
+	IMustLock(h_dir);
+
+	h_path.dentry = au_whtmp_lkup(h_parent, br, &h_dentry->d_name);
+	err = PTR_ERR(h_path.dentry);
+	if (IS_ERR(h_path.dentry))
+		goto out;
+
+	/* under the same dir, no need to lock_rename() */
+	delegated = NULL;
+	err = vfsub_rename(h_dir, h_dentry, h_dir, &h_path, &delegated,
+			   /*flags*/0);
+	AuTraceErr(err);
+	if (unlikely(err == -EWOULDBLOCK)) {
+		pr_warn("cannot retry for NFSv4 delegation"
+			" for an internal rename\n");
+		iput(delegated);
+	}
+	dput(h_path.dentry);
+
+out:
+	AuTraceErr(err);
+	return err;
+}
+
 /* ---------------------------------------------------------------------- */
 /*
  * functions for removing a whiteout
@@ -194,6 +232,27 @@ int au_wh_unlink_dentry(struct inode *h_dir, struct path *h_path,
 	return err;
 }
 
+static int unlink_wh_name(struct dentry *h_parent, struct qstr *wh,
+			  struct au_branch *br)
+{
+	int err;
+	struct path h_path = {
+		.mnt = au_br_mnt(br)
+	};
+
+	err = 0;
+	h_path.dentry = vfsub_lkup_one(wh, h_parent);
+	if (IS_ERR(h_path.dentry))
+		err = PTR_ERR(h_path.dentry);
+	else {
+		if (d_is_reg(h_path.dentry))
+			err = do_unlink_wh(d_inode(h_parent), &h_path);
+		dput(h_path.dentry);
+	}
+
+	return err;
+}
+
 /* ---------------------------------------------------------------------- */
 /*
  * initialize/clean whiteout for a branch
@@ -743,3 +802,243 @@ struct dentry *au_wh_create(struct dentry *dentry, aufs_bindex_t bindex,
 
 	return wh_dentry;
 }
+
+/* ---------------------------------------------------------------------- */
+
+/* Delete all whiteouts in this directory on branch bindex. */
+static int del_wh_children(struct dentry *h_dentry, struct au_nhash *whlist,
+			   aufs_bindex_t bindex, struct au_branch *br)
+{
+	int err;
+	unsigned long ul, n;
+	struct qstr wh_name;
+	char *p;
+	struct hlist_head *head;
+	struct au_vdir_wh *pos;
+	struct au_vdir_destr *str;
+
+	err = -ENOMEM;
+	p = (void *)__get_free_page(GFP_NOFS);
+	wh_name.name = p;
+	if (unlikely(!wh_name.name))
+		goto out;
+
+	err = 0;
+	memcpy(p, AUFS_WH_PFX, AUFS_WH_PFX_LEN);
+	p += AUFS_WH_PFX_LEN;
+	n = whlist->nh_num;
+	head = whlist->nh_head;
+	for (ul = 0; !err && ul < n; ul++, head++) {
+		hlist_for_each_entry(pos, head, wh_hash) {
+			if (pos->wh_bindex != bindex)
+				continue;
+
+			str = &pos->wh_str;
+			if (str->len + AUFS_WH_PFX_LEN <= PATH_MAX) {
+				memcpy(p, str->name, str->len);
+				wh_name.len = AUFS_WH_PFX_LEN + str->len;
+				err = unlink_wh_name(h_dentry, &wh_name, br);
+				if (!err)
+					continue;
+				break;
+			}
+			AuIOErr("whiteout name too long %.*s\n",
+				str->len, str->name);
+			err = -EIO;
+			break;
+		}
+	}
+	free_page((unsigned long)wh_name.name);
+
+out:
+	return err;
+}
+
+struct del_wh_children_args {
+	int *errp;
+	struct dentry *h_dentry;
+	struct au_nhash *whlist;
+	aufs_bindex_t bindex;
+	struct au_branch *br;
+};
+
+static void call_del_wh_children(void *args)
+{
+	struct del_wh_children_args *a = args;
+	*a->errp = del_wh_children(a->h_dentry, a->whlist, a->bindex, a->br);
+}
+
+/* ---------------------------------------------------------------------- */
+
+struct au_whtmp_rmdir *au_whtmp_rmdir_alloc(struct super_block *sb, gfp_t gfp)
+{
+	struct au_whtmp_rmdir *whtmp;
+	int err;
+	unsigned int rdhash;
+
+	SiMustAnyLock(sb);
+
+	whtmp = kzalloc(sizeof(*whtmp), gfp);
+	if (unlikely(!whtmp)) {
+		whtmp = ERR_PTR(-ENOMEM);
+		goto out;
+	}
+
+	/* no estimation for dir size */
+	rdhash = au_sbi(sb)->si_rdhash;
+	if (!rdhash)
+		rdhash = AUFS_RDHASH_DEF;
+	err = au_nhash_alloc(&whtmp->whlist, rdhash, gfp);
+	if (unlikely(err)) {
+		au_kfree_rcu(whtmp);
+		whtmp = ERR_PTR(err);
+	}
+
+out:
+	return whtmp;
+}
+
+void au_whtmp_rmdir_free(struct au_whtmp_rmdir *whtmp)
+{
+	if (whtmp->br)
+		au_lcnt_dec(&whtmp->br->br_count);
+	dput(whtmp->wh_dentry);
+	iput(whtmp->dir);
+	au_nhash_wh_free(&whtmp->whlist);
+	au_kfree_rcu(whtmp);
+}
+
+/*
+ * rmdir the whiteouted temporary named dir @h_dentry.
+ * @whlist: whiteouted children.
+ */
+int au_whtmp_rmdir(struct inode *dir, aufs_bindex_t bindex,
+		   struct dentry *wh_dentry, struct au_nhash *whlist)
+{
+	int err;
+	unsigned int h_nlink;
+	struct path h_tmp;
+	struct inode *wh_inode, *h_dir;
+	struct au_branch *br;
+
+	h_dir = d_inode(wh_dentry->d_parent); /* dir inode is locked */
+	IMustLock(h_dir);
+
+	br = au_sbr(dir->i_sb, bindex);
+	wh_inode = d_inode(wh_dentry);
+	inode_lock_nested(wh_inode, AuLsc_I_CHILD);
+
+	/*
+	 * someone else might change some whiteouts while we were sleeping.
+	 * it means this whlist may have an obsoleted entry.
+	 */
+	if (!au_test_h_perm_sio(wh_inode, MAY_EXEC | MAY_WRITE))
+		err = del_wh_children(wh_dentry, whlist, bindex, br);
+	else {
+		int wkq_err;
+		struct del_wh_children_args args = {
+			.errp		= &err,
+			.h_dentry	= wh_dentry,
+			.whlist		= whlist,
+			.bindex		= bindex,
+			.br		= br
+		};
+
+		wkq_err = au_wkq_wait(call_del_wh_children, &args);
+		if (unlikely(wkq_err))
+			err = wkq_err;
+	}
+	inode_unlock(wh_inode);
+
+	if (!err) {
+		h_tmp.dentry = wh_dentry;
+		h_tmp.mnt = au_br_mnt(br);
+		h_nlink = h_dir->i_nlink;
+		err = vfsub_rmdir(h_dir, &h_tmp);
+		/* some fs doesn't change the parent nlink in some cases */
+		h_nlink -= h_dir->i_nlink;
+	}
+
+	if (!err) {
+		if (au_ibtop(dir) == bindex) {
+			/* todo: dir->i_mutex is necessary */
+			au_cpup_attr_timesizes(dir);
+			if (h_nlink)
+				vfsub_drop_nlink(dir);
+		}
+		return 0; /* success */
+	}
+
+	pr_warn("failed removing %pd(%d), ignored\n", wh_dentry, err);
+	return err;
+}
+
+static void call_rmdir_whtmp(void *args)
+{
+	int err;
+	aufs_bindex_t bindex;
+	struct au_whtmp_rmdir *a = args;
+	struct super_block *sb;
+	struct dentry *h_parent;
+	struct inode *h_dir;
+	struct au_hinode *hdir;
+
+	/* rmdir by nfsd may cause deadlock with this i_mutex */
+	/* inode_lock(a->dir); */
+	err = -EROFS;
+	sb = a->dir->i_sb;
+	si_read_lock(sb, !AuLock_FLUSH);
+	if (!au_br_writable(a->br->br_perm))
+		goto out;
+	bindex = au_br_index(sb, a->br->br_id);
+	if (unlikely(bindex < 0))
+		goto out;
+
+	err = -EIO;
+	ii_write_lock_parent(a->dir);
+	h_parent = dget_parent(a->wh_dentry);
+	h_dir = d_inode(h_parent);
+	hdir = au_hi(a->dir, bindex);
+	err = vfsub_mnt_want_write(au_br_mnt(a->br));
+	if (unlikely(err))
+		goto out_mnt;
+	au_hn_inode_lock_nested(hdir, AuLsc_I_PARENT);
+	err = au_h_verify(a->wh_dentry, au_opt_udba(sb), h_dir, h_parent,
+			  a->br);
+	if (!err)
+		err = au_whtmp_rmdir(a->dir, bindex, a->wh_dentry, &a->whlist);
+	au_hn_inode_unlock(hdir);
+	vfsub_mnt_drop_write(au_br_mnt(a->br));
+
+out_mnt:
+	dput(h_parent);
+	ii_write_unlock(a->dir);
+out:
+	/* inode_unlock(a->dir); */
+	au_whtmp_rmdir_free(a);
+	si_read_unlock(sb);
+	au_nwt_done(&au_sbi(sb)->si_nowait);
+	if (unlikely(err))
+		AuIOErr("err %d\n", err);
+}
+
+void au_whtmp_kick_rmdir(struct inode *dir, aufs_bindex_t bindex,
+			 struct dentry *wh_dentry, struct au_whtmp_rmdir *args)
+{
+	int wkq_err;
+	struct super_block *sb;
+
+	IMustLock(dir);
+
+	/* all post-process will be done in do_rmdir_whtmp(). */
+	sb = dir->i_sb;
+	args->dir = au_igrab(dir);
+	args->br = au_sbr(sb, bindex);
+	au_lcnt_inc(&args->br->br_count);
+	args->wh_dentry = dget(wh_dentry);
+	wkq_err = au_wkq_nowait(call_rmdir_whtmp, args, sb, /*flags*/0);
+	if (unlikely(wkq_err)) {
+		pr_warn("rmdir error %pd (%d), ignored\n", wh_dentry, wkq_err);
+		au_whtmp_rmdir_free(args);
+	}
+}

fs/aufs/whout.h

@@ -12,20 +12,18 @@
 
 #ifdef __KERNEL__
 
+#include "dir.h"
+
 /* whout.c */
-struct qstr;
 int au_wh_name_alloc(struct qstr *wh, const struct qstr *name);
-struct dentry;
 int au_wh_test(struct dentry *h_parent, struct qstr *wh_name, int try_sio);
 int au_diropq_test(struct dentry *h_dentry);
 struct au_branch;
 struct dentry *au_whtmp_lkup(struct dentry *h_parent, struct au_branch *br,
 			     struct qstr *prefix);
-struct inode;
-struct path;
+int au_whtmp_ren(struct dentry *h_dentry, struct au_branch *br);
 int au_wh_unlink_dentry(struct inode *h_dir, struct path *h_path,
 			struct dentry *dentry);
-struct super_block;
 int au_wh_init(struct au_branch *br, struct super_block *sb);
 
 /* diropq flags */
@@ -43,6 +41,21 @@ struct dentry *au_wh_lkup(struct dentry *h_parent, struct qstr *base_name,
 struct dentry *au_wh_create(struct dentry *dentry, aufs_bindex_t bindex,
 			    struct dentry *h_parent);
 
+/* real rmdir for the whiteout-ed dir */
+struct au_whtmp_rmdir {
+	struct inode *dir;
+	struct au_branch *br;
+	struct dentry *wh_dentry;
+	struct au_nhash whlist;
+};
+
+struct au_whtmp_rmdir *au_whtmp_rmdir_alloc(struct super_block *sb, gfp_t gfp);
+void au_whtmp_rmdir_free(struct au_whtmp_rmdir *whtmp);
+int au_whtmp_rmdir(struct inode *dir, aufs_bindex_t bindex,
+		   struct dentry *wh_dentry, struct au_nhash *whlist);
+void au_whtmp_kick_rmdir(struct inode *dir, aufs_bindex_t bindex,
+			 struct dentry *wh_dentry, struct au_whtmp_rmdir *args);
+
 /* ---------------------------------------------------------------------- */
 
 static inline struct dentry *au_diropq_create(struct dentry *dentry,