path: root/fs/xfs/xfs_rtbitmap.c

/*
 * Copyright (c) 2000-2005 Silicon Graphics, Inc.
 * 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 as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it would 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 the Free Software Foundation,
 * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */
#include "xfs.h"
#include "xfs_fs.h"
#include "xfs_shared.h"
#include "xfs_format.h"
#include "xfs_log_format.h"
#include "xfs_trans_resv.h"
#include "xfs_bit.h"
#include "xfs_sb.h"
#include "xfs_ag.h"
#include "xfs_mount.h"
#include "xfs_inode.h"
#include "xfs_bmap.h"
#include "xfs_bmap_util.h"
#include "xfs_bmap_btree.h"
#include "xfs_alloc.h"
#include "xfs_error.h"
#include "xfs_trans.h"
#include "xfs_trans_space.h"
#include "xfs_trace.h"
#include "xfs_buf.h"
#include "xfs_icache.h"
#include "xfs_dinode.h"
#include "xfs_rtalloc.h"


/*
 * Realtime allocator bitmap functions shared with userspace.
 */

/*
 * Get a buffer for the bitmap or summary file block specified.
 * The buffer is returned read and locked.
 */
int
xfs_rtbuf_get(
	xfs_mount_t	*mp,		/* file system mount structure */
	xfs_trans_t	*tp,		/* transaction pointer */
	xfs_rtblock_t	block,		/* block number in bitmap or summary */
	int		issum,		/* is summary not bitmap */
	xfs_buf_t	**bpp)		/* output: buffer for the block */
{
	xfs_buf_t	*bp;		/* block buffer, result */
	xfs_inode_t	*ip;		/* bitmap or summary inode */
	xfs_bmbt_irec_t	map;
	int		nmap = 1;
	int		error;		/* error value */

	ip = issum ? mp->m_rsumip : mp->m_rbmip;

	error = xfs_bmapi_read(ip, block, 1, &map, &nmap, XFS_DATA_FORK);
	if (error)
		return error;

	ASSERT(map.br_startblock != NULLFSBLOCK);
	error = xfs_trans_read_buf(mp, tp, mp->m_ddev_targp,
				   XFS_FSB_TO_DADDR(mp, map.br_startblock),
				   mp->m_bsize, 0, &bp, NULL);
	if (error)
		return error;
	*bpp = bp;
	return 0;
}

/*
 * Searching backward from start to limit, find the first block whose
 * allocated/free state is different from start's.
 */
int
xfs_rtfind_back(
	xfs_mount_t	*mp,		/* file system mount point */
	xfs_trans_t	*tp,		/* transaction pointer */
	xfs_rtblock_t	start,		/* starting block to look at */
	xfs_rtblock_t	limit,		/* last block to look at */
	xfs_rtblock_t	*rtblock)	/* out: start block found */
{
	xfs_rtword_t	*b;		/* current word in buffer */
	int		bit;		/* bit number in the word */
	xfs_rtblock_t	block;		/* bitmap block number */
	xfs_buf_t	*bp;		/* buf for the block */
	xfs_rtword_t	*bufp;		/* starting word in buffer */
	int		error;		/* error value */
	xfs_rtblock_t	firstbit;	/* first useful bit in the word */
	xfs_rtblock_t	i;		/* current bit number rel. to start */
	xfs_rtblock_t	len;		/* length of inspected area */
	xfs_rtword_t	mask;		/* mask of relevant bits for value */
	xfs_rtword_t	want;		/* mask for "good" values */
	xfs_rtword_t	wdiff;		/* difference from wanted value */
	int		word;		/* word number in the buffer */

	/*
	 * Compute and read in starting bitmap block for starting block.
	 */
	block = XFS_BITTOBLOCK(mp, start);
	error = xfs_rtbuf_get(mp, tp, block, 0, &bp);
	if (error) {
		return error;
	}
	bufp = bp->b_addr;
	/*
	 * Get the first word's index & point to it.
	 */
	word = XFS_BITTOWORD(mp, start);
	b = &bufp[word];
	bit = (int)(start & (XFS_NBWORD - 1));
	len = start - limit + 1;
	/*
	 * Compute match value, based on the bit at start: if 1 (free)
	 * then all-ones, else all-zeroes.
	 */
	want = (*b & ((xfs_rtword_t)1 << bit)) ? -1 : 0;
	/*
	 * If the starting position is not word-aligned, deal with the
	 * partial word.
	 */
	if (bit < XFS_NBWORD - 1) {
		/*
		 * Calculate first (leftmost) bit number to look at,
		 * and mask for all the relevant bits in this word.
		 */
		firstbit = XFS_RTMAX((xfs_srtblock_t)(bit - len + 1), 0);
		mask = (((xfs_rtword_t)1 << (bit - firstbit + 1)) - 1) <<
			firstbit;
		/*
		 * Calculate the difference between the value there
		 * and what we're looking for.
		 */
		if ((wdiff = (*b ^ want) & mask)) {
			/*
			 * Different.  Mark where we are and return.
			 */
			xfs_trans_brelse(tp, bp);
			i = bit - XFS_RTHIBIT(wdiff);
			*rtblock = start - i + 1;
			return 0;
		}
		i = bit - firstbit + 1;
		/*
		 * Go on to previous block if that's where the previous word is
		 * and we need the previous word.
		 */
		if (--word == -1 && i < len) {
			/*
			 * If done with this block, get the previous one.
			 */
			xfs_trans_brelse(tp, bp);
			error = xfs_rtbuf_get(mp, tp, --