/*
 * Copyright (C) 2005-2013 Junjiro R. Okajima
 *
 * This program, aufs is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */

/*
 * sub-routines for dentry cache
 */

#include "aufs.h"

static void au_dpage_free(struct au_dpage *dpage)
{
	int i;
	struct dentry **p;

	p = dpage->dentries;
	for (i = 0; i < dpage->ndentry; i++)
		dput(*p++);
	free_page((unsigned long)dpage->dentries);
}

int au_dpages_init(struct au_dcsub_pages *dpages, gfp_t gfp)
{
	int err;
	void *p;

	err = -ENOMEM;
	dpages->dpages = kmalloc(sizeof(*dpages->dpages), gfp);
	if (unlikely(!dpages->dpages))
		goto out;

	p = (void *)__get_free_page(gfp);
	if (unlikely(!p))
		goto out_dpages;

	dpages->dpages[0].ndentry = 0;
	dpages->dpages[0].dentries = p;
	dpages->ndpage = 1;
	return 0; /* success */

out_dpages:
	kfree(dpages->dpages);
out:
	return err;
}

void au_dpages_free(struct au_dcsub_pages *dpages)
{
	int i;
	struct au_dpage *p;

	p = dpages->dpages;
	for (i = 0; i < dpages->ndpage; i++)
		au_dpage_free(p++);
	kfree(dpages->dpages);
}

static int au_dpages_append(struct au_dcsub_pages *dpages,
			    struct dentry *dentry, gfp_t gfp)
{
	int err, sz;
	struct au_dpage *dpage;
	void *p;

	dpage = dpages->dpages + dpages->ndpage - 1;
	sz = PAGE_SIZE / sizeof(dentry);
	if (unlikely(dpage->ndentry >= sz)) {
		AuLabel(new dpage);
		err = -ENOMEM;
		sz = dpages->ndpage * sizeof(*dpages->dpages);
		p = au_kzrealloc(dpages->dpages, sz,
				 sz + sizeof(*dpages->dpages), gfp);
		if (unlikely(!p))
			goto out;

		dpages->dpages = p;
		dpage = dpages->dpages + dpages->ndpage;
		p = (void *)__get_free_page(gfp);
		if (unlikely(!p))
			goto out;

		dpage->ndentry = 0;
		dpage->dentries = p;
		dpages->ndpage++;
	}

	AuDebugOn(!dentry->d_count);
	dpage->dentries[dpage->ndentry++] = dget_dlock(dentry);
	return 0; /* success */

out:
	return err;
}

int au_dcsub_pages(struct au_dcsub_pages *dpages, struct dentry *root,
		   au_dpages_test test, void *arg)
{
	int err;
	struct dentry *this_parent;
	struct list_head *next;
	struct super_block *sb = root->d_sb;

	err = 0;
	write_seqlock(&rename_lock);
	this_parent = root;
	spin_lock(&this_parent->d_lock);
repeat:
	next = this_parent->d_subdirs.next;
resume:
	if (this_parent->d_sb == sb
	    && !IS_ROOT(this_parent)
	    && au_di(this_parent)
	    && this_parent->d_count
	    && (!test || test(this_parent, arg))) {
		err = au_dpages_append(dpages, this_parent, GFP_ATOMIC);
		if (unlikely(err))
			goto out;
	}

	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 (dentry->d_count) {
			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_sb == sb
			    && au_di(dentry)
			    && (!test || test(dentry, arg)))
				err = au_dpages_append(dpages, dentry,
						       GFP_ATOMIC);
		}
		spin_unlock(&dentry->d_lock);
		if (unlikely(err))
			goto out;
	}

	if (this_parent != root) {
		struct dentry *tmp;
		struct dentry *child;

		tmp = this_parent->d_parent;
		rcu_read_lock();
		spin_unlock(&this_parent->d_lock);
		child = this_parent;
		this_parent = tmp;
		spin_lock(&this_parent->d_lock);
		rcu_read_unlock();
		next = child->d_u.d_child.next;
		goto resume;
	}

out:
	spin_unlock(&this_parent->d_lock);
	write_sequnlock(&rename_lock);
	return err;
}

int au_dcsub_pages_rev(struct au_dcsub_pages *dpages, struct dentry *dentry,
		       int do_include, au_dpages_test test, void *arg)
{
	int err;

	err = 0;
	write_seqlock(&rename_lock);
	spin_lock(&dentry->d_lock);
	if (do_include
	    && dentry->d_count
	    && (!test || test(dentry, arg)))
		err = au_dpages_append(dpages, dentry, GFP_ATOMIC);
	spin_unlock(&dentry->d_lock);
	if (unlikely(err))
		goto out;

	/*
	 * vfsmount_lock is unnecessary since this is a traverse in a single
	 * mount
	 */
	while (!IS_ROOT(dentry)) {
		dentry = dentry->d_parent; /* rename_lock is locked */
		spin_lock(&dentry->d_lock);
		if (dentry->d_count
		    && (!test || test(dentry, arg)))
			err = au_dpages_append(dpages, dentry, GFP_ATOMIC);
		spin_unlock(&dentry->d_lock);
		if (unlikely(err))
			break;
	}

out:
	write_sequnlock(&rename_lock);
	return err;
}

static inline int au_dcsub_dpages_aufs(struct dentry *dentry, void *arg)
{
	return au_di(dentry) && dentry->d_sb == arg;
}

int au_dcsub_pages_rev_aufs(struct au_dcsub_pages *dpages,
			    struct dentry *dentry, int do_include)
{
	return au_dcsub_pages_rev(dpages, dentry, do_include,
				  au_dcsub_dpages_aufs, dentry->d_sb);
}

int au_test_subdir(struct dentry *d1, struct dentry *d2)
{
	struct path path[2] = {
		{
			.dentry = d1
		},
		{
			.dentry = d2
		}
	};

	return path_is_under(path + 0, path + 1);
}