diff options
Diffstat (limited to 'fs/xfs/xfs_btree.c')
| -rw-r--r-- | fs/xfs/xfs_btree.c | 219 |
1 files changed, 219 insertions, 0 deletions
diff --git a/fs/xfs/xfs_btree.c b/fs/xfs/xfs_btree.c index 3d561f8..41912a0 100644 --- a/fs/xfs/xfs_btree.c +++ b/fs/xfs/xfs_btree.c @@ -1270,3 +1270,222 @@ error0: return error; } + +STATIC int +xfs_btree_lookup_get_block( + struct xfs_btree_cur *cur, /* btree cursor */ + int level, /* level in the btree */ + union xfs_btree_ptr *pp, /* ptr to btree block */ + struct xfs_btree_block **blkp) /* return btree block */ +{ + struct xfs_buf *bp; /* buffer pointer for btree block */ + int error = 0; + + /* special case the root block if in an inode */ + if ((cur->bc_flags & XFS_BTREE_ROOT_IN_INODE) && + (level == cur->bc_nlevels - 1)) { + *blkp = xfs_btree_get_iroot(cur); + return 0; + } + + /* + * If the old buffer at this level for the disk address we are + * looking for re-use it. + * + * Otherwise throw it away and get a new one. + */ + bp = cur->bc_bufs[level]; + if (bp && XFS_BUF_ADDR(bp) == xfs_btree_ptr_to_daddr(cur, pp)) { + *blkp = XFS_BUF_TO_BLOCK(bp); + return 0; + } + + error = xfs_btree_read_buf_block(cur, pp, level, 0, blkp, &bp); + if (error) + return error; + + xfs_btree_setbuf(cur, level, bp); + return 0; +} + +/* + * Get current search key. For level 0 we don't actually have a key + * structure so we make one up from the record. For all other levels + * we just return the right key. + */ +STATIC union xfs_btree_key * +xfs_lookup_get_search_key( + struct xfs_btree_cur *cur, + int level, + int keyno, + struct xfs_btree_block *block, + union xfs_btree_key *kp) +{ + if (level == 0) { + cur->bc_ops->init_key_from_rec(kp, + xfs_btree_rec_addr(cur, keyno, block)); + return kp; + } + + return xfs_btree_key_addr(cur, keyno, block); +} + +/* + * 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. + */ +int /* error */ +xfs_btree_lookup( + struct xfs_btree_cur *cur, /* btree cursor */ + xfs_lookup_t dir, /* <=, ==, or >= */ + int *stat) /* success/failure */ +{ + struct xfs_btree_block *block; /* current btree block */ + __int64_t diff; /* difference for the current key */ + int error; /* error return value */ + int keyno; /* current key number */ + int level; /* level in the btree */ + union xfs_btree_ptr *pp; /* ptr to btree block */ + union xfs_btree_ptr ptr; /* ptr to btree block */ + + XFS_BTREE_TRACE_CURSOR(cur, XBT_ENTRY); + XFS_BTREE_TRACE_ARGI(cur, dir); + + XFS_BTREE_STATS_INC(cur, lookup); + + block = NULL; + keyno = 0; + + /* initialise start pointer from cursor */ + cur->bc_ops->init_ptr_from_cur(cur, &ptr); + pp = &ptr; + + /* + * 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--) { + /* Get the block we need to do the lookup on. */ + error = xfs_btree_lookup_get_block(cur, level, pp, &block); + if (error) + goto error0; + + if (diff == 0) { + /* + * If we already had a key match at a higher level, we + * know we need to use the first entry in this block. + */ + keyno = 1; + } else { + /* Otherwise search this block. Do a binary search. */ + + int high; /* high entry number */ + int low; /* low entry number */ + + /* Set low and high entry numbers, 1-based. */ + low = 1; + high = xfs_btree_get_numrecs(block); + if (!high) { + /* Block is empty, must be an empty leaf. */ + ASSERT(level == 0 && cur->bc_nlevels == 1); + + cur->bc_ptrs[0] = dir != XFS_LOOKUP_LE; + XFS_BTREE_TRACE_CURSOR(cur, XBT_EXIT); + *stat = 0; + return 0; + } + + /* Binary search the block. */ + while (low <= high) { + union xfs_btree_key key; + union xfs_btree_key *kp; + + XFS_BTREE_STATS_INC(cur, compare); + + /* keyno is average of low and high. */ + keyno = (low + high) >> 1; + + /* Get current search key */ + kp = xfs_lookup_get_search_key(cur, level, + keyno, block, &key); + + /* + * Compute difference to get next direction: + * - less than, move right + * - greater than, move left + * - equal, we're done + */ + diff = cur->bc_ops->key_diff(cur, kp); + if (diff < 0) + low = keyno + 1; + else if (diff > 0) + high = keyno - 1; + 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; + pp = xfs_btree_ptr_addr(cur, keyno, block); + +#ifdef DEBUG + error = xfs_btree_check_ptr(cur, pp, 0, level); + if (error) + goto error0; +#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. + */ + xfs_btree_get_sibling(cur, block, &ptr, XFS_BB_RIGHTSIB); + if (dir == XFS_LOOKUP_GE && + keyno > xfs_btree_get_numrecs(block) && + !xfs_btree_ptr_is_null(cur, &ptr)) { + int i; + + cur->bc_ptrs[0] = keyno; + error = xfs_btree_increment(cur, 0, &i); + if (error) + goto error0; + XFS_WANT_CORRUPTED_RETURN(i == 1); + XFS_BTREE_TRACE_CURSOR(cur, XBT_EXIT); + *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 > xfs_btree_get_numrecs(block)) + *stat = 0; + else if (dir != XFS_LOOKUP_EQ || diff == 0) + *stat = 1; + else + *stat = 0; + XFS_BTREE_TRACE_CURSOR(cur, XBT_EXIT); + return 0; + +error0: + XFS_BTREE_TRACE_CURSOR(cur, XBT_ERROR); + return error; +} |