/*
 * Copyright (C) 2005-2010 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
 */

/*
 * dentry private data
 */

#include "aufs.h"

void au_di_init_once(void *_dinfo)
{
	struct au_dinfo *dinfo = _dinfo;
	static struct lock_class_key aufs_di;

	au_rw_init(&dinfo->di_rwsem);
	au_rw_class(&dinfo->di_rwsem, &aufs_di);
}

int au_di_init(struct dentry *dentry)
{
	struct au_dinfo *dinfo;
	struct super_block *sb;
	int nbr;

	dinfo = au_cache_alloc_dinfo();
	if (unlikely(!dinfo))
		goto out;

	sb = dentry->d_sb;
	nbr = au_sbend(sb) + 1;
	if (nbr <= 0)
		nbr = 1;
	dinfo->di_hdentry = kcalloc(nbr, sizeof(*dinfo->di_hdentry), GFP_NOFS);
	if (unlikely(!dinfo->di_hdentry))
		goto out_dinfo;

	atomic_set(&dinfo->di_generation, au_sigen(sb));
	/* smp_mb(); */ /* atomic_set */
	au_rw_write_lock_nested(&dinfo->di_rwsem, AuLsc_DI_CHILD);
	dinfo->di_bstart = -1;
	dinfo->di_bend = -1;
	dinfo->di_bwh = -1;
	dinfo->di_bdiropq = -1;

	dentry->d_fsdata = dinfo;
	dentry->d_op = &aufs_dop;
	return 0; /* success */

out_dinfo:
	au_cache_free_dinfo(dinfo);
out:
	return -ENOMEM;
}

void au_di_fin(struct dentry *dentry)
{
	struct au_dinfo *di;
	struct au_hdentry *p;
	aufs_bindex_t bend, bindex;

	/* dentry may not be revalidated */
	di = dentry->d_fsdata;
	bindex = di->di_bstart;
	if (bindex >= 0) {
		bend = di->di_bend;
		p = di->di_hdentry + bindex;
		while (bindex++ <= bend)
			au_hdput(p++);
	}
	kfree(di->di_hdentry);
	AuRwDestroy(&di->di_rwsem);
	au_cache_free_dinfo(di);
}

int au_di_realloc(struct au_dinfo *dinfo, int nbr)
{
	int err, sz;
	struct au_hdentry *hdp;

	AuRwMustWriteLock(&dinfo->di_rwsem);

	err = -ENOMEM;
	sz = sizeof(*hdp) * (dinfo->di_bend + 1);
	if (!sz)
		sz = sizeof(*hdp);
	hdp = au_kzrealloc(dinfo->di_hdentry, sz, sizeof(*hdp) * nbr, GFP_NOFS);
	if (hdp) {
		dinfo->di_hdentry = hdp;
		err = 0;
	}

	return err;
}

/* ---------------------------------------------------------------------- */

static void do_ii_write_lock(struct inode *inode, unsigned int lsc)
{
	switch (lsc) {
	case AuLsc_DI_CHILD:
		ii_write_lock_child(inode);
		break;
	case AuLsc_DI_CHILD2:
		ii_write_lock_child2(inode);
		break;
	case AuLsc_DI_CHILD3:
		ii_write_lock_child3(inode);
		break;
	case AuLsc_DI_PARENT:
		ii_write_lock_parent(inode);
		break;
	case AuLsc_DI_PARENT2:
		ii_write_lock_parent2(inode);
		break;
	case AuLsc_DI_PARENT3:
		ii_write_lock_parent3(inode);
		break;
	default:
		BUG();
	}
}

static void do_ii_read_lock(struct inode *inode, unsigned int lsc)
{
	switch (lsc) {
	case AuLsc_DI_CHILD:
		ii_read_lock_child(inode);
		break;
	case AuLsc_DI_CHILD2:
		ii_read_lock_child2(inode);
		break;
	case AuLsc_DI_CHILD3:
		ii_read_lock_child3(inode);
		break;
	case AuLsc_DI_PARENT:
		ii_read_lock_parent(inode);
		break;
	case AuLsc_DI_PARENT2:
		ii_read_lock_parent2(inode);
		break;
	case AuLsc_DI_PARENT3:
		ii_read_lock_parent3(inode);
		break;
	default:
		BUG();
	}
}

void di_read_lock(struct dentry *d, int flags, unsigned int lsc)
{
	au_rw_read_lock_nested(&au_di(d)->di_rwsem, lsc);
	if (d->d_inode) {
		if (au_ftest_lock(flags, IW))
			do_ii_write_lock(d->d_inode, lsc);
		else if (au_ftest_lock(flags, IR))
			do_ii_read_lock(d->d_inode, lsc);
	}
}

void di_read_unlock(struct dentry *d, int flags)
{
	if (d->d_inode) {
		if (au_ftest_lock(flags, IW))
			ii_write_unlock(d->d_inode);
		else if (au_ftest_lock(flags, IR))
			ii_read_unlock(d->d_inode);
	}
	au_rw_read_unlock(&au_di(d)->di_rwsem);
}

void di_downgrade_lock(struct dentry *d, int flags)
{
	if (d->d_inode && au_ftest_lock(flags, IR))
		ii_downgrade_lock(d->d_inode);
	au_rw_dgrade_lock(&au_di(d)->di_rwsem);
}

void di_write_lock(struct dentry *d, unsigned int lsc)
{
	au_rw_write_lock_nested(&au_di(d)->di_rwsem, lsc);
	if (d->d_inode)
		do_ii_write_lock(d->d_inode, lsc);
}

void di_write_unlock(struct dentry *d)
{
	if (d->d_inode)
		ii_write_unlock(d->d_inode);
	au_rw_write_unlock(&au_di(d)->di_rwsem);
}

void di_write_lock2_child(struct dentry *d1, struct dentry *d2, int isdir)
{
	AuDebugOn(d1 == d2
		  || d1->d_inode == d2->d_inode
		  || d1->d_sb != d2->d_sb);

	if (isdir && au_test_subdir(d1, d2)) {
		di_write_lock_child(d1);
		di_write_lock_child2(d2);
	} else {
		/* there should be no races */
		di_write_lock_child(d2);
		di_write_lock_child2(d1);
	}
}

void di_write_lock2_parent(struct dentry *d1, struct dentry *d2, int isdir)
{
	AuDebugOn(d1 == d2
		  || d1->d_inode == d2->d_inode
		  || d1->d_sb != d2->d_sb);

	if (isdir && au_test_subdir(d1, d2)) {
		di_write_lock_parent(d1);
		di_write_lock_parent2(d2);
	} else {
		/* there should be no races */
		di_write_lock_parent(d2);
		di_write_lock_parent2(d1);
	}
}

void di_write_unlock2(struct dentry *d1, struct dentry *d2)
{
	di_write_unlock(d1);
	if (d1->d_inode == d2->d_inode)
		au_rw_write_unlock(&au_di(d2)->di_rwsem);
	else
		di_write_unlock(d2);
}

/* ---------------------------------------------------------------------- */

struct dentry *au_h_dptr(struct dentry *dentry, aufs_bindex_t bindex)
{
	struct dentry *d;

	DiMustAnyLock(dentry);

	if (au_dbstart(dentry) < 0 || bindex < au_dbstart(dentry))
		return NULL;
	AuDebugOn(bindex < 0);
	d = au_di(dentry)->di_hdentry[0 + bindex].hd_dentry;
	AuDebugOn(d && (atomic_read(&d->d_count) <= 0));
	return d;
}

aufs_bindex_t au_dbtail(struct dentry *dentry)
{
	aufs_bindex_t bend, bwh;

	bend = au_dbend(dentry);
	if (0 <= bend) {
		bwh = au_dbwh(dentry);
		if (!bwh)
			return bwh;
		if (0 < bwh && bwh < bend)
			return bwh - 1;
	}
	return bend;
}

aufs_bindex_t au_dbtaildir(struct dentry *dentry)
{
	aufs_bindex_t bend, bopq;

	bend = au_dbtail(dentry);
	if (0 <= bend) {
		bopq = au_dbdiropq(dentry);
		if (0 <= bopq && bopq < bend)
			bend = bopq;
	}
	return bend;
}

/* ---------------------------------------------------------------------- */

void au_set_h_dptr(struct dentry *dentry, aufs_bindex_t bindex,
		   struct dentry *h_dentry)
{
	struct au_hdentry *hd = au_di(dentry)->di_hdentry + bindex;

	DiMustWriteLock(dentry);

	au_hdput(hd);
	hd->hd_dentry = h_dentry;
}

void au_update_digen(struct dentry *dentry)
{
	atomic_set(&au_di(dentry)->di_generation, au_sigen(dentry->d_sb));
	/* smp_mb(); */ /* atomic_set */
}

void au_update_dbrange(struct dentry *dentry, int do_put_zero)
{
	struct au_dinfo *dinfo;
	struct dentry *h_d;
	struct au_hdentry *hdp;

	DiMustWriteLock(dentry);

	dinfo = au_di(dentry);
	if (!dinfo || dinfo->di_bstart < 0)
		return;

	hdp = dinfo->di_hdentry;
	if (do_put_zero) {
		aufs_bindex_t bindex, bend;

		bend = dinfo->di_bend;
		for (bindex = dinfo->di_bstart; bindex <= bend; bindex++) {
			h_d = hdp[0 + bindex].hd_dentry;
			if (h_d && !h_d->d_inode)
				au_set_h_dptr(dentry, bindex, NULL);
		}
	}

	dinfo->di_bstart = -1;
	while (++dinfo->di_bstart <= dinfo->di_bend)
		if (hdp[0 + dinfo->di_bstart].hd_dentry)
			break;
	if (dinfo->di_bstart > dinfo->di_bend) {
		dinfo->di_bstart = -1;
		dinfo->di_bend = -1;
		return;
	}

	dinfo->di_bend++;
	while (0 <= --dinfo->di_bend)
		if (hdp[0 + dinfo->di_bend].hd_dentry)
			break;
	AuDebugOn(dinfo->di_bstart > dinfo->di_bend || dinfo->di_bend < 0);
}

void au_update_dbstart(struct dentry *dentry)
{
	aufs_bindex_t bindex, bend;
	struct dentry *h_dentry;

	bend = au_dbend(dentry);
	for (bindex = au_dbstart(dentry); bindex <= bend; bindex++) {
		h_dentry = au_h_dptr(dentry, bindex);
		if (!h_dentry)
			continue;
		if (h_dentry->d_inode) {
			au_set_dbstart(dentry, bindex);
			return;
		}
		au_set_h_dptr(dentry, bindex, NULL);
	}
}

void au_update_dbend(struct dentry *dentry)
{
	aufs_bindex_t bindex, bstart;
	struct dentry *h_dentry;

	bstart = au_dbstart(dentry);
	for (bindex = au_dbend(dentry); bindex <= bstart; bindex--) {
		h_dentry = au_h_dptr(dentry, bindex);
		if (!h_dentry)
			continue;
		if (h_dentry->d_inode) {
			au_set_dbend(dentry, bindex);
			return;
		}
		au_set_h_dptr(dentry, bindex, NULL);
	}
}

int au_find_dbindex(struct dentry *dentry, struct dentry *h_dentry)
{
	aufs_bindex_t bindex, bend;

	bend = au_dbend(dentry);
	for (bindex = au_dbstart(dentry); bindex <= bend; bindex++)
		if (au_h_dptr(dentry, bindex) == h_dentry)
			return bindex;
	return -1;
}