[XFS] implement generic xfs_btree_decrement

[~andy/linux] / fs / xfs / xfs_btree.c

diff --git a/fs/xfs/xfs_btree.c b/fs/xfs/xfs_btree.c
index e9ab86b7990e47f10e2d28f461cce9feb7b860ce..3d561f8f78d043cf6a2eb7b0ff725723c69d6bdb 100644 (file)
--- a/fs/xfs/xfs_btree.c
+++ b/fs/xfs/xfs_btree.c
@@ -1171,3 +1171,102 @@ error0:
        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;
+}
+