xfs_alloc_btree.c

linux 内核源代码

 */
STATIC void
xfs_alloc_log_ptrs(
	xfs_btree_cur_t		*cur,	/* btree cursor */
	xfs_buf_t		*bp,	/* buffer containing btree block */
	int			pfirst,	/* index of first pointer to log */
	int			plast)	/* index of last pointer to log */
{
	xfs_alloc_block_t	*block;	/* btree block to log from */
	int			first;	/* first byte offset logged */
	int			last;	/* last byte offset logged */
	xfs_alloc_ptr_t		*pp;	/* block-pointer pointer in btree blk */

	block = XFS_BUF_TO_ALLOC_BLOCK(bp);
	pp = XFS_ALLOC_PTR_ADDR(block, 1, cur);
	first = (int)((xfs_caddr_t)&pp[pfirst - 1] - (xfs_caddr_t)block);
	last = (int)(((xfs_caddr_t)&pp[plast] - 1) - (xfs_caddr_t)block);
	xfs_trans_log_buf(cur->bc_tp, bp, first, last);
}

/*
 * Log records from a btree block (leaf).
 */
STATIC void
xfs_alloc_log_recs(
	xfs_btree_cur_t		*cur,	/* btree cursor */
	xfs_buf_t		*bp,	/* buffer containing btree block */
	int			rfirst,	/* index of first record to log */
	int			rlast)	/* index of last record to log */
{
	xfs_alloc_block_t	*block;	/* btree block to log from */
	int			first;	/* first byte offset logged */
	int			last;	/* last byte offset logged */
	xfs_alloc_rec_t		*rp;	/* record pointer for btree block */


	block = XFS_BUF_TO_ALLOC_BLOCK(bp);
	rp = XFS_ALLOC_REC_ADDR(block, 1, cur);
#ifdef DEBUG
	{
		xfs_agf_t	*agf;
		xfs_alloc_rec_t	*p;

		agf = XFS_BUF_TO_AGF(cur->bc_private.a.agbp);
		for (p = &rp[rfirst - 1]; p <= &rp[rlast - 1]; p++)
			ASSERT(be32_to_cpu(p->ar_startblock) +
			       be32_to_cpu(p->ar_blockcount) <=
			       be32_to_cpu(agf->agf_length));
	}
#endif
	first = (int)((xfs_caddr_t)&rp[rfirst - 1] - (xfs_caddr_t)block);
	last = (int)(((xfs_caddr_t)&rp[rlast] - 1) - (xfs_caddr_t)block);
	xfs_trans_log_buf(cur->bc_tp, bp, first, last);
}

/*
 * Lookup the record.  The cursor is made to point to it, based on dir.
 * Return 0 if can't find any such record, 1 for success.
 */
STATIC int				/* error */
xfs_alloc_lookup(
	xfs_btree_cur_t		*cur,	/* btree cursor */
	xfs_lookup_t		dir,	/* <=, ==, or >= */
	int			*stat)	/* success/failure */
{
	xfs_agblock_t		agbno;	/* a.g. relative btree block number */
	xfs_agnumber_t		agno;	/* allocation group number */
	xfs_alloc_block_t	*block=NULL;	/* current btree block */
	int			diff;	/* difference for the current key */
	int			error;	/* error return value */
	int			keyno=0;	/* current key number */
	int			level;	/* level in the btree */
	xfs_mount_t		*mp;	/* file system mount point */

	XFS_STATS_INC(xs_abt_lookup);
	/*
	 * Get the allocation group header, and the root block number.
	 */
	mp = cur->bc_mp;

	{
		xfs_agf_t	*agf;	/* a.g. freespace header */

		agf = XFS_BUF_TO_AGF(cur->bc_private.a.agbp);
		agno = be32_to_cpu(agf->agf_seqno);
		agbno = be32_to_cpu(agf->agf_roots[cur->bc_btnum]);
	}
	/*
	 * Iterate over each level in the btree, starting at the root.
	 * For each level above the leaves, find the key we need, based
	 * on the lookup record, then follow the corresponding block
	 * pointer down to the next level.
	 */
	for (level = cur->bc_nlevels - 1, diff = 1; level >= 0; level--) {
		xfs_buf_t	*bp;	/* buffer pointer for btree block */
		xfs_daddr_t	d;	/* disk address of btree block */

		/*
		 * Get the disk address we're looking for.
		 */
		d = XFS_AGB_TO_DADDR(mp, agno, agbno);
		/*
		 * If the old buffer at this level is for a different block,
		 * throw it away, otherwise just use it.
		 */
		bp = cur->bc_bufs[level];
		if (bp && XFS_BUF_ADDR(bp) != d)
			bp = NULL;
		if (!bp) {
			/*
			 * Need to get a new buffer.  Read it, then
			 * set it in the cursor, releasing the old one.
			 */
			if ((error = xfs_btree_read_bufs(mp, cur->bc_tp, agno,
					agbno, 0, &bp, XFS_ALLOC_BTREE_REF)))
				return error;
			xfs_btree_setbuf(cur, level, bp);
			/*
			 * Point to the btree block, now that we have the buffer
			 */
			block = XFS_BUF_TO_ALLOC_BLOCK(bp);
			if ((error = xfs_btree_check_sblock(cur, block, level,
					bp)))
				return error;
		} else
			block = XFS_BUF_TO_ALLOC_BLOCK(bp);
		/*
		 * If we already had a key match at a higher level, we know
		 * we need to use the first entry in this block.
		 */
		if (diff == 0)
			keyno = 1;
		/*
		 * Otherwise we need to search this block.  Do a binary search.
		 */
		else {
			int		high;	/* high entry number */
			xfs_alloc_key_t	*kkbase=NULL;/* base of keys in block */
			xfs_alloc_rec_t	*krbase=NULL;/* base of records in block */
			int		low;	/* low entry number */

			/*
			 * Get a pointer to keys or records.
			 */
			if (level > 0)
				kkbase = XFS_ALLOC_KEY_ADDR(block, 1, cur);
			else
				krbase = XFS_ALLOC_REC_ADDR(block, 1, cur);
			/*
			 * Set low and high entry numbers, 1-based.
			 */
			low = 1;
			if (!(high = be16_to_cpu(block->bb_numrecs))) {
				/*
				 * If the block is empty, the tree must
				 * be an empty leaf.
				 */
				ASSERT(level == 0 && cur->bc_nlevels == 1);
				cur->bc_ptrs[0] = dir != XFS_LOOKUP_LE;
				*stat = 0;
				return 0;
			}
			/*
			 * Binary search the block.
			 */
			while (low <= high) {
				xfs_extlen_t	blockcount;	/* key value */
				xfs_agblock_t	startblock;	/* key value */

				XFS_STATS_INC(xs_abt_compare);
				/*
				 * keyno is average of low and high.
				 */
				keyno = (low + high) >> 1;
				/*
				 * Get startblock & blockcount.
				 */
				if (level > 0) {
					xfs_alloc_key_t	*kkp;

					kkp = kkbase + keyno - 1;
					startblock = be32_to_cpu(kkp->ar_startblock);
					blockcount = be32_to_cpu(kkp->ar_blockcount);
				} else {
					xfs_alloc_rec_t	*krp;

					krp = krbase + keyno - 1;
					startblock = be32_to_cpu(krp->ar_startblock);
					blockcount = be32_to_cpu(krp->ar_blockcount);
				}
				/*
				 * Compute difference to get next direction.
				 */
				if (cur->bc_btnum == XFS_BTNUM_BNO)
					diff = (int)startblock -
					       (int)cur->bc_rec.a.ar_startblock;
				else if (!(diff = (int)blockcount -
					    (int)cur->bc_rec.a.ar_blockcount))
					diff = (int)startblock -
					    (int)cur->bc_rec.a.ar_startblock;
				/*
				 * Less than, move right.
				 */
				if (diff < 0)
					low = keyno + 1;
				/*
				 * Greater than, move left.
				 */
				else if (diff > 0)
					high = keyno - 1;
				/*
				 * Equal, we're done.
				 */
				else
					break;
			}
		}
		/*
		 * If there are more levels, set up for the next level
		 * by getting the block number and filling in the cursor.
		 */
		if (level > 0) {
			/*
			 * If we moved left, need the previous key number,
			 * unless there isn't one.
			 */
			if (diff > 0 && --keyno < 1)
				keyno = 1;
			agbno = be32_to_cpu(*XFS_ALLOC_PTR_ADDR(block, keyno, cur));
#ifdef DEBUG
			if ((error = xfs_btree_check_sptr(cur, agbno, level)))
				return error;
#endif
			cur->bc_ptrs[level] = keyno;
		}
	}
	/*
	 * Done with the search.
	 * See if we need to adjust the results.
	 */
	if (dir != XFS_LOOKUP_LE && diff < 0) {
		keyno++;
		/*
		 * If ge search and we went off the end of the block, but it's
		 * not the last block, we're in the wrong block.
		 */
		if (dir == XFS_LOOKUP_GE &&
		    keyno > be16_to_cpu(block->bb_numrecs) &&
		    be32_to_cpu(block->bb_rightsib) != NULLAGBLOCK) {
			int	i;

			cur->bc_ptrs[0] = keyno;
			if ((error = xfs_alloc_increment(cur, 0, &i)))
				return error;
			XFS_WANT_CORRUPTED_RETURN(i == 1);
			*stat = 1;
			return 0;
		}
	}
	else if (dir == XFS_LOOKUP_LE && diff > 0)
		keyno--;
	cur->bc_ptrs[0] = keyno;
	/*
	 * Return if we succeeded or not.
	 */
	if (keyno == 0 || keyno > be16_to_cpu(block->bb_numrecs))
		*stat = 0;
	else
		*stat = ((dir != XFS_LOOKUP_EQ) || (diff == 0));
	return 0;
}

/*
 * Move 1 record left from cur/level if possible.
 * Update cur to reflect the new path.
 */
STATIC int				/* error */
xfs_alloc_lshift(
	xfs_btree_cur_t		*cur,	/* btree cursor */
	int			level,	/* level to shift record on */
	int			*stat)	/* success/failure */
{
	int			error;	/* error return value */
#ifdef DEBUG
	int			i;	/* loop index */
#endif
	xfs_alloc_key_t		key;	/* key value for leaf level upward */
	xfs_buf_t		*lbp;	/* buffer for left neighbor block */
	xfs_alloc_block_t	*left;	/* left neighbor btree block */
	int			nrec;	/* new number of left block entries */
	xfs_buf_t		*rbp;	/* buffer for right (current) block */
	xfs_alloc_block_t	*right;	/* right (current) btree block */
	xfs_alloc_key_t		*rkp=NULL;	/* key pointer for right block */
	xfs_alloc_ptr_t		*rpp=NULL;	/* address pointer for right block */
	xfs_alloc_rec_t		*rrp=NULL;	/* record pointer for right block */

	/*
	 * Set up variables for this block as "right".
	 */
	rbp = cur->bc_bufs[level];
	right = XFS_BUF_TO_ALLOC_BLOCK(rbp);
#ifdef DEBUG
	if ((error = xfs_btree_check_sblock(cur, right, level, rbp)))
		return error;
#endif
	/*
	 * If we've got no left sibling then we can't shift an entry left.
	 */
	if (be32_to_cpu(right->bb_leftsib) == NULLAGBLOCK) {
		*stat = 0;
		return 0;
	}
	/*
	 * If the cursor entry is the one that would be moved, don't
	 * do it... it's too complicated.
	 */
	if (cur->bc_ptrs[level] <= 1) {
		*stat = 0;
		return 0;
	}
	/*
	 * Set up the left neighbor as "left".
	 */
	if ((error = xfs_btree_read_bufs(cur->bc_mp, cur->bc_tp,
			cur->bc_private.a.agno, be32_to_cpu(right->bb_leftsib),
			0, &lbp, XFS_ALLOC_BTREE_REF)))
		return error;
	left = XFS_BUF_TO_ALLOC_BLOCK(lbp);
	if ((error = xfs_btree_check_sblock(cur, left, level, lbp)))
		return error;
	/*
	 * If it's full, it can't take another entry.
	 */
	if (be16_to_cpu(left->bb_numrecs) == XFS_ALLOC_BLOCK_MAXRECS(level, cur)) {
		*stat = 0;
		return 0;
	}
	nrec = be16_to_cpu(left->bb_numrecs) + 1;
	/*
	 * If non-leaf, copy a key and a ptr to the left block.
	 */
	if (level > 0) {
		xfs_alloc_key_t	*lkp;	/* key pointer for left block */
		xfs_alloc_ptr_t	*lpp;	/* address pointer for left block */

		lkp = XFS_ALLOC_KEY_ADDR(left, nrec, cur);
		rkp = XFS_ALLOC_KEY_ADDR(right, 1, cur);
		*lkp = *rkp;
		xfs_alloc_log_keys(cur, lbp, nrec, nrec);
		lpp = XFS_ALLOC_PTR_ADDR(left, nrec, cur);
		rpp = XFS_ALLOC_PTR_ADDR(right, 1, cur);
#ifdef DEBUG
		if ((error = xfs_btree_check_sptr(cur, be32_to_cpu(*rpp), level)))
			return error;
#endif
		*lpp = *rpp;
		xfs_alloc_log_ptrs(cur, lbp, nrec, nrec);
		xfs_btree_check_key(cur->bc_btnum, lkp - 1, lkp);
	}
	/*
	 * If leaf, copy a record to the left block.
	 */
	else {
		xfs_alloc_rec_t	*lrp;	/* record pointer for left block */

		lrp = XFS_ALLOC_REC_ADDR(left, nrec, cur);
		rrp = XFS_ALLOC_REC_ADDR(right, 1, cur);
		*lrp = *rrp;
		xfs_alloc_log_recs(cur, lbp, nrec, nrec);
		xfs_btree_check_rec(cur->bc_btnum, lrp - 1, lrp);
	}
	/*
	 * Bump and log left's numrecs, decrement and log right's numrecs.
	 */
	be16_add(&left->bb_numrecs, 1);
	xfs_alloc_log_block(cur->bc_tp, lbp, XFS_BB_NUMRECS);
	be16_add(&right->bb_numrecs, -1);
	xfs_alloc_log_block(cur->bc_tp, rbp, XFS_BB_NUMRECS);
	/*
	 * Slide the contents of right down one entry.
	 */
	if (level > 0) {
#ifdef DEBUG
		for (i = 0; i < be16_to_cpu(right->bb_numrecs); i++) {
			if ((error = xfs_btree_check_sptr(cur, be32_to_cpu(rpp[i + 1]),
					level)))
				return error;
		}
#endif
		memmove(rkp, rkp + 1, be16_to_cpu(right->bb_numrecs) * sizeof(*rkp));
		memmove(rpp, rpp + 1, be16_to_cpu(right->bb_numrecs) * sizeof(*rpp));
		xfs_alloc_log_keys(cur, rbp, 1, be16_to_cpu(right->bb_numrecs));
		xfs_alloc_log_ptrs(cur, rbp, 1, be16_to_cpu(right->bb_numrecs));
	} else {
		memmove(rrp, rrp + 1, be16_to_cpu(right->bb_numrecs) * sizeof(*rrp));
		xfs_alloc_log_recs(cur, rbp, 1, be16_to_cpu(right->bb_numrecs));
		key.ar_startblock = rrp->ar_startblock;
		key.ar_blockcount = rrp->ar_blockcount;
		rkp = &key;
	}
	/*
	 * Update the parent key values of right.
	 */
	if ((error = xfs_alloc_updkey(cur, rkp, level + 1)))
		return error;
	/*
	 * Slide the cursor value left one.
	 */
	cur->bc_ptrs[level]--;
	*stat = 1;
	return 0;
}

/*
 * Allocate a new root block, fill it in.
 */
STATIC int				/* error */
xfs_alloc_newroot(
	xfs_btree_cur_t		*cur,	/* btree cursor */
	int			*stat)	/* success/failure */
{
	int			error;	/* error return value */
	xfs_agblock_t		lbno;	/* left block number */
	xfs_buf_t		*lbp;	/* left btree buffer */
	xfs_alloc_block_t	*left;	/* left btree block */
	xfs_mount_t		*mp;	/* mount structure */
	xfs_agblock_t		nbno;	/* new block number */
	xfs_buf_t		*nbp;	/* new (root) buffer */
	xfs_alloc_block_t	*new;	/* new (root) btree block */
	int			nptr;	/* new value for key index, 1 or 2 */
	xfs_agblock_t		rbno;	/* right block number */
	xfs_buf_t		*rbp;	/* right btree buffer */
	xfs_alloc_block_t	*right;	/* right btree block */

	mp = cur->bc_mp;

	ASSERT(cur->bc_nlevels < XFS_AG_MAXLEVELS(mp));
	/*
	 * Get a buffer from the freelist blocks, for the new root.
	 */
	error = xfs_alloc_get_freelist(cur->bc_tp,
					cur->bc_private.a.agbp, &nbno, 1);