[XFS] implement generic xfs_btree_lookup
From: Dave Chinner <dgc@sgi.com> [hch: split out from bigger patch and minor adaptions] SGI-PV: 985583 SGI-Modid: xfs-linux-melb:xfs-kern:32192a Signed-off-by: Christoph Hellwig <hch@infradead.org> Signed-off-by: Lachlan McIlroy <lachlan@sgi.com> Signed-off-by: Bill O'Donnell <billodo@sgi.com> Signed-off-by: David Chinner <david@fromorbit.com>
This commit is contained in:
Christoph Hellwig
committed by
Lachlan McIlroy
Lachlan McIlroy
parent
8df4da4a0a
commit
fe033cc848
@@ -1270,3 +1270,222 @@ error0:
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return error;
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}
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STATIC int
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xfs_btree_lookup_get_block(
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struct xfs_btree_cur *cur, /* btree cursor */
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int level, /* level in the btree */
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union xfs_btree_ptr *pp, /* ptr to btree block */
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struct xfs_btree_block **blkp) /* return btree block */
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{
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struct xfs_buf *bp; /* buffer pointer for btree block */
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int error = 0;
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/* special case the root block if in an inode */
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if ((cur->bc_flags & XFS_BTREE_ROOT_IN_INODE) &&
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(level == cur->bc_nlevels - 1)) {
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*blkp = xfs_btree_get_iroot(cur);
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return 0;
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}
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/*
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* If the old buffer at this level for the disk address we are
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* looking for re-use it.
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*
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* Otherwise throw it away and get a new one.
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*/
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bp = cur->bc_bufs[level];
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if (bp && XFS_BUF_ADDR(bp) == xfs_btree_ptr_to_daddr(cur, pp)) {
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*blkp = XFS_BUF_TO_BLOCK(bp);
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return 0;
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}
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error = xfs_btree_read_buf_block(cur, pp, level, 0, blkp, &bp);
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if (error)
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return error;
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xfs_btree_setbuf(cur, level, bp);
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return 0;
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}
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/*
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* Get current search key. For level 0 we don't actually have a key
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* structure so we make one up from the record. For all other levels
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* we just return the right key.
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*/
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STATIC union xfs_btree_key *
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xfs_lookup_get_search_key(
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struct xfs_btree_cur *cur,
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int level,
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int keyno,
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struct xfs_btree_block *block,
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union xfs_btree_key *kp)
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{
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if (level == 0) {
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cur->bc_ops->init_key_from_rec(kp,
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xfs_btree_rec_addr(cur, keyno, block));
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return kp;
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}
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return xfs_btree_key_addr(cur, keyno, block);
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}
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/*
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* Lookup the record. The cursor is made to point to it, based on dir.
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* Return 0 if can't find any such record, 1 for success.
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*/
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int /* error */
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xfs_btree_lookup(
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struct xfs_btree_cur *cur, /* btree cursor */
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xfs_lookup_t dir, /* <=, ==, or >= */
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int *stat) /* success/failure */
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{
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struct xfs_btree_block *block; /* current btree block */
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__int64_t diff; /* difference for the current key */
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int error; /* error return value */
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int keyno; /* current key number */
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int level; /* level in the btree */
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union xfs_btree_ptr *pp; /* ptr to btree block */
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union xfs_btree_ptr ptr; /* ptr to btree block */
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XFS_BTREE_TRACE_CURSOR(cur, XBT_ENTRY);
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XFS_BTREE_TRACE_ARGI(cur, dir);
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XFS_BTREE_STATS_INC(cur, lookup);
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block = NULL;
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keyno = 0;
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/* initialise start pointer from cursor */
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cur->bc_ops->init_ptr_from_cur(cur, &ptr);
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pp = &ptr;
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/*
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* Iterate over each level in the btree, starting at the root.
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* For each level above the leaves, find the key we need, based
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* on the lookup record, then follow the corresponding block
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* pointer down to the next level.
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*/
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for (level = cur->bc_nlevels - 1, diff = 1; level >= 0; level--) {
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/* Get the block we need to do the lookup on. */
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error = xfs_btree_lookup_get_block(cur, level, pp, &block);
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if (error)
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goto error0;
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if (diff == 0) {
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/*
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* If we already had a key match at a higher level, we
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* know we need to use the first entry in this block.
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*/
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keyno = 1;
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} else {
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/* Otherwise search this block. Do a binary search. */
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int high; /* high entry number */
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int low; /* low entry number */
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/* Set low and high entry numbers, 1-based. */
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low = 1;
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high = xfs_btree_get_numrecs(block);
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if (!high) {
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/* Block is empty, must be an empty leaf. */
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ASSERT(level == 0 && cur->bc_nlevels == 1);
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cur->bc_ptrs[0] = dir != XFS_LOOKUP_LE;
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XFS_BTREE_TRACE_CURSOR(cur, XBT_EXIT);
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*stat = 0;
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return 0;
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}
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/* Binary search the block. */
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while (low <= high) {
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union xfs_btree_key key;
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union xfs_btree_key *kp;
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XFS_BTREE_STATS_INC(cur, compare);
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/* keyno is average of low and high. */
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keyno = (low + high) >> 1;
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/* Get current search key */
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kp = xfs_lookup_get_search_key(cur, level,
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keyno, block, &key);
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/*
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* Compute difference to get next direction:
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* - less than, move right
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* - greater than, move left
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* - equal, we're done
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*/
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diff = cur->bc_ops->key_diff(cur, kp);
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if (diff < 0)
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low = keyno + 1;
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else if (diff > 0)
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high = keyno - 1;
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else
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break;
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}
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}
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/*
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* If there are more levels, set up for the next level
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* by getting the block number and filling in the cursor.
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*/
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if (level > 0) {
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/*
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* If we moved left, need the previous key number,
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* unless there isn't one.
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*/
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if (diff > 0 && --keyno < 1)
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keyno = 1;
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pp = xfs_btree_ptr_addr(cur, keyno, block);
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#ifdef DEBUG
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error = xfs_btree_check_ptr(cur, pp, 0, level);
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if (error)
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goto error0;
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#endif
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cur->bc_ptrs[level] = keyno;
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}
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}
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/* Done with the search. See if we need to adjust the results. */
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if (dir != XFS_LOOKUP_LE && diff < 0) {
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keyno++;
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/*
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* If ge search and we went off the end of the block, but it's
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* not the last block, we're in the wrong block.
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*/
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xfs_btree_get_sibling(cur, block, &ptr, XFS_BB_RIGHTSIB);
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if (dir == XFS_LOOKUP_GE &&
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keyno > xfs_btree_get_numrecs(block) &&
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!xfs_btree_ptr_is_null(cur, &ptr)) {
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int i;
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cur->bc_ptrs[0] = keyno;
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error = xfs_btree_increment(cur, 0, &i);
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if (error)
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goto error0;
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XFS_WANT_CORRUPTED_RETURN(i == 1);
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XFS_BTREE_TRACE_CURSOR(cur, XBT_EXIT);
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*stat = 1;
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return 0;
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}
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} else if (dir == XFS_LOOKUP_LE && diff > 0)
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keyno--;
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cur->bc_ptrs[0] = keyno;
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/* Return if we succeeded or not. */
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if (keyno == 0 || keyno > xfs_btree_get_numrecs(block))
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*stat = 0;
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else if (dir != XFS_LOOKUP_EQ || diff == 0)
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*stat = 1;
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else
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*stat = 0;
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XFS_BTREE_TRACE_CURSOR(cur, XBT_EXIT);
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return 0;
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error0:
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XFS_BTREE_TRACE_CURSOR(cur, XBT_ERROR);
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return error;
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}
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