xfs_rtalloc.c

linux 内核源代码

	xfs_rtblock_t	lastbit;	/* last useful bit in word */
	xfs_rtword_t	mask;		/* mask of relevant bits for value */
	xfs_rtword_t	wdiff;		/* difference from wanted value */
	int		word;		/* word number in the buffer */

	/*
	 * Compute starting bitmap block number
	 */
	block = XFS_BITTOBLOCK(mp, start);
	/*
	 * Read the bitmap block.
	 */
	error = xfs_rtbuf_get(mp, tp, block, 0, &bp);
	if (error) {
		return error;
	}
	bufp = (xfs_rtword_t *)XFS_BUF_PTR(bp);
	/*
	 * Compute the starting word's address, and starting bit.
	 */
	word = XFS_BITTOWORD(mp, start);
	b = &bufp[word];
	bit = (int)(start & (XFS_NBWORD - 1));
	/*
	 * 0 (allocated) => all zero's; 1 (free) => all one's.
	 */
	val = -val;
	/*
	 * If not starting on a word boundary, deal with the first
	 * (partial) word.
	 */
	if (bit) {
		/*
		 * Compute first bit not examined.
		 */
		lastbit = XFS_RTMIN(bit + len, XFS_NBWORD);
		/*
		 * Mask of relevant bits.
		 */
		mask = (((xfs_rtword_t)1 << (lastbit - bit)) - 1) << bit;
		/*
		 * Compute difference between actual and desired value.
		 */
		if ((wdiff = (*b ^ val) & mask)) {
			/*
			 * Different, compute first wrong bit and return.
			 */
			xfs_trans_brelse(tp, bp);
			i = XFS_RTLOBIT(wdiff) - bit;
			*new = start + i;
			*stat = 0;
			return 0;
		}
		i = lastbit - bit;
		/*
		 * Go on to next block if that's where the next word is
		 * and we need the next word.
		 */
		if (++word == XFS_BLOCKWSIZE(mp) && i < len) {
			/*
			 * If done with this block, get the next one.
			 */
			xfs_trans_brelse(tp, bp);
			error = xfs_rtbuf_get(mp, tp, ++block, 0, &bp);
			if (error) {
				return error;
			}
			b = bufp = (xfs_rtword_t *)XFS_BUF_PTR(bp);
			word = 0;
		} else {
			/*
			 * Go on to the next word in the buffer.
			 */
			b++;
		}
	} else {
		/*
		 * Starting on a word boundary, no partial word.
		 */
		i = 0;
	}
	/*
	 * Loop over whole words in buffers.  When we use up one buffer
	 * we move on to the next one.
	 */
	while (len - i >= XFS_NBWORD) {
		/*
		 * Compute difference between actual and desired value.
		 */
		if ((wdiff = *b ^ val)) {
			/*
			 * Different, compute first wrong bit and return.
			 */
			xfs_trans_brelse(tp, bp);
			i += XFS_RTLOBIT(wdiff);
			*new = start + i;
			*stat = 0;
			return 0;
		}
		i += XFS_NBWORD;
		/*
		 * Go on to next block if that's where the next word is
		 * and we need the next word.
		 */
		if (++word == XFS_BLOCKWSIZE(mp) && i < len) {
			/*
			 * If done with this block, get the next one.
			 */
			xfs_trans_brelse(tp, bp);
			error = xfs_rtbuf_get(mp, tp, ++block, 0, &bp);
			if (error) {
				return error;
			}
			b = bufp = (xfs_rtword_t *)XFS_BUF_PTR(bp);
			word = 0;
		} else {
			/*
			 * Go on to the next word in the buffer.
			 */
			b++;
		}
	}
	/*
	 * If not ending on a word boundary, deal with the last
	 * (partial) word.
	 */
	if ((lastbit = len - i)) {
		/*
		 * Mask of relevant bits.
		 */
		mask = ((xfs_rtword_t)1 << lastbit) - 1;
		/*
		 * Compute difference between actual and desired value.
		 */
		if ((wdiff = (*b ^ val) & mask)) {
			/*
			 * Different, compute first wrong bit and return.
			 */
			xfs_trans_brelse(tp, bp);
			i += XFS_RTLOBIT(wdiff);
			*new = start + i;
			*stat = 0;
			return 0;
		} else
			i = len;
	}
	/*
	 * Successful, return.
	 */
	xfs_trans_brelse(tp, bp);
	*new = start + i;
	*stat = 1;
	return 0;
}

/*
 * Copy and transform the summary file, given the old and new
 * parameters in the mount structures.
 */
STATIC int				/* error */
xfs_rtcopy_summary(
	xfs_mount_t	*omp,		/* old file system mount point */
	xfs_mount_t	*nmp,		/* new file system mount point */
	xfs_trans_t	*tp)		/* transaction pointer */
{
	xfs_rtblock_t	bbno;		/* bitmap block number */
	xfs_buf_t	*bp;		/* summary buffer */
	int		error;		/* error return value */
	int		log;		/* summary level number (log length) */
	xfs_suminfo_t	sum;		/* summary data */
	xfs_fsblock_t	sumbno;		/* summary block number */

	bp = NULL;
	for (log = omp->m_rsumlevels - 1; log >= 0; log--) {
		for (bbno = omp->m_sb.sb_rbmblocks - 1;
		     (xfs_srtblock_t)bbno >= 0;
		     bbno--) {
			error = xfs_rtget_summary(omp, tp, log, bbno, &bp,
				&sumbno, &sum);
			if (error)
				return error;
			if (sum == 0)
				continue;
			error = xfs_rtmodify_summary(omp, tp, log, bbno, -sum,
				&bp, &sumbno);
			if (error)
				return error;
			error = xfs_rtmodify_summary(nmp, tp, log, bbno, sum,
				&bp, &sumbno);
			if (error)
				return error;
			ASSERT(sum > 0);
		}
	}
	return 0;
}

/*
 * Searching backward from start to limit, find the first block whose
 * allocated/free state is different from start's.
 */
STATIC int				/* error */
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 = (xfs_rtword_t *)XFS_BUF_PTR(bp);
	/*
	 * 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, --block, 0, &bp);
			if (error) {
				return error;
			}
			bufp = (xfs_rtword_t *)XFS_BUF_PTR(bp);
			word = XFS_BLOCKWMASK(mp);
			b = &bufp[word];
		} else {
			/*
			 * Go on to the previous word in the buffer.
			 */
			b--;
		}
	} else {
		/*
		 * Starting on a word boundary, no partial word.
		 */
		i = 0;
	}
	/*
	 * Loop over whole words in buffers.  When we use up one buffer
	 * we move on to the previous one.
	 */
	while (len - i >= XFS_NBWORD) {
		/*
		 * Compute difference between actual and desired value.
		 */
		if ((wdiff = *b ^ want)) {
			/*
			 * Different, mark where we are and return.
			 */
			xfs_trans_brelse(tp, bp);
			i += XFS_NBWORD - 1 - XFS_RTHIBIT(wdiff);
			*rtblock = start - i + 1;
			return 0;
		}
		i += XFS_NBWORD;
		/*
		 * 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, --block, 0, &bp);
			if (error) {
				return error;
			}
			bufp = (xfs_rtword_t *)XFS_BUF_PTR(bp);
			word = XFS_BLOCKWMASK(mp);
			b = &bufp[word];
		} else {
			/*
			 * Go on to the previous word in the buffer.
			 */
			b--;
		}
	}
	/*
	 * If not ending on a word boundary, deal with the last
	 * (partial) word.
	 */
	if (len - i) {
		/*
		 * Calculate first (leftmost) bit number to look at,
		 * and mask for all the relevant bits in this word.
		 */
		firstbit = XFS_NBWORD - (len - i);
		mask = (((xfs_rtword_t)1 << (len - i)) - 1) << firstbit;
		/*
		 * Compute difference between actual and desired value.
		 */
		if ((wdiff = (*b ^ want) & mask)) {
			/*
			 * Different, mark where we are and return.
			 */
			xfs_trans_brelse(tp, bp);
			i += XFS_NBWORD - 1 - XFS_RTHIBIT(wdiff);
			*rtblock = start - i + 1;
			return 0;
		} else
			i = len;
	}
	/*
	 * No match, return that we scanned the whole area.
	 */
	xfs_trans_brelse(tp, bp);
	*rtblock = start - i + 1;
	return 0;
}

/*
 * Searching forward from start to limit, find the first block whose
 * allocated/free state is different from start's.
 */
STATIC int				/* error */
xfs_rtfind_forw(
	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	i;		/* current bit number rel. to start */
	xfs_rtblock_t	lastbit;	/* last useful bit in the word */
	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 = (xfs_rtword_t *)XFS_BUF_PTR(bp);
	/*
	 * Get the first word's index & point to it.
	 */
	word = XFS_BITTOWORD(mp, start);
	b = &bufp[word];
	bit = (int)(start & (XFS_NBWORD - 1));
	len = limit - start + 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) {
		/*
		 * Calculate last (rightmost) bit number to look at,
		 * and mask for all the relevant bits in this word.
		 */
		lastbit = XFS_RTMIN(bit + len, XFS_NBWORD);
		mask = (((xfs_rtword_t)1 << (lastbit - bit)) - 1) << bit;
		/*
		 * 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 = XFS_RTLOBIT(wdiff) - bit;
			*rtblock = start + i - 1;
			return 0;
		}
		i = lastbit - bit;
		/*
		 * Go on to next block if that's where the next word is
		 * and we need the next word.
		 */
		if (++word == XFS_BLOCKWSIZE(mp) && i < len) {
			/*
			 * If done with this block, get the previous one.
			 */
			xfs_trans_brelse(tp, bp);
			error = xfs_rtbuf_get(mp, tp, ++block, 0, &bp);
			if (error) {
				return error;
			}
			b = bufp = (xfs_rtword_t *)XFS_BUF_PTR(bp);
			word = 0;
		} else {
			/*
			 * Go on to the previous word in the buffer.
			 */
			b++;
		}
	} else {
		/*
		 * Starting on a word boundary, no partial word.