[XFS] implement generic xfs_btree_decrement
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:32191a
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>
diff --git a/fs/xfs/xfs_btree.c b/fs/xfs/xfs_btree.c
index e9ab86b..3d561f8 100644
--- a/fs/xfs/xfs_btree.c
+++ b/fs/xfs/xfs_btree.c
@@ -1171,3 +1171,102 @@
XFS_BTREE_TRACE_CURSOR(cur, XBT_ERROR);
return error;
}
+
+/*
+ * Decrement cursor by one record at the level.
+ * For nonzero levels the leaf-ward information is untouched.
+ */
+int /* error */
+xfs_btree_decrement(
+ struct xfs_btree_cur *cur,
+ int level,
+ int *stat) /* success/failure */
+{
+ struct xfs_btree_block *block;
+ xfs_buf_t *bp;
+ int error; /* error return value */
+ int lev;
+ union xfs_btree_ptr ptr;
+
+ XFS_BTREE_TRACE_CURSOR(cur, XBT_ENTRY);
+ XFS_BTREE_TRACE_ARGI(cur, level);
+
+ ASSERT(level < cur->bc_nlevels);
+
+ /* Read-ahead to the left at this level. */
+ xfs_btree_readahead(cur, level, XFS_BTCUR_LEFTRA);
+
+ /* We're done if we remain in the block after the decrement. */
+ if (--cur->bc_ptrs[level] > 0)
+ goto out1;
+
+ /* Get a pointer to the btree block. */
+ block = xfs_btree_get_block(cur, level, &bp);
+
+#ifdef DEBUG
+ error = xfs_btree_check_block(cur, block, level, bp);
+ if (error)
+ goto error0;
+#endif
+
+ /* Fail if we just went off the left edge of the tree. */
+ xfs_btree_get_sibling(cur, block, &ptr, XFS_BB_LEFTSIB);
+ if (xfs_btree_ptr_is_null(cur, &ptr))
+ goto out0;
+
+ XFS_BTREE_STATS_INC(cur, decrement);
+
+ /*
+ * March up the tree decrementing pointers.
+ * Stop when we don't go off the left edge of a block.
+ */
+ for (lev = level + 1; lev < cur->bc_nlevels; lev++) {
+ if (--cur->bc_ptrs[lev] > 0)
+ break;
+ /* Read-ahead the left block for the next loop. */
+ xfs_btree_readahead(cur, lev, XFS_BTCUR_LEFTRA);
+ }
+
+ /*
+ * If we went off the root then we are seriously confused.
+ * or the root of the tree is in an inode.
+ */
+ if (lev == cur->bc_nlevels) {
+ if (cur->bc_flags & XFS_BTREE_ROOT_IN_INODE)
+ goto out0;
+ ASSERT(0);
+ error = EFSCORRUPTED;
+ goto error0;
+ }
+ ASSERT(lev < cur->bc_nlevels);
+
+ /*
+ * Now walk back down the tree, fixing up the cursor's buffer
+ * pointers and key numbers.
+ */
+ for (block = xfs_btree_get_block(cur, lev, &bp); lev > level; ) {
+ union xfs_btree_ptr *ptrp;
+
+ ptrp = xfs_btree_ptr_addr(cur, cur->bc_ptrs[lev], block);
+ error = xfs_btree_read_buf_block(cur, ptrp, --lev,
+ 0, &block, &bp);
+ if (error)
+ goto error0;
+ xfs_btree_setbuf(cur, lev, bp);
+ cur->bc_ptrs[lev] = xfs_btree_get_numrecs(block);
+ }
+out1:
+ XFS_BTREE_TRACE_CURSOR(cur, XBT_EXIT);
+ *stat = 1;
+ return 0;
+
+out0:
+ XFS_BTREE_TRACE_CURSOR(cur, XBT_EXIT);
+ *stat = 0;
+ return 0;
+
+error0:
+ XFS_BTREE_TRACE_CURSOR(cur, XBT_ERROR);
+ return error;
+}
+