+/*
+ * Modify inode page cache in such way:
+ * have - blocks with b_blocknr equal to oldb...oldb+count-1
+ * get - blocks with b_blocknr equal to newb...newb+count-1
+ * also we suppose that oldb...oldb+count-1 blocks
+ * situated at the end of file.
+ *
+ * We can come here from ufs_writepage or ufs_prepare_write,
+ * locked_page is argument of these functions, so we already lock it.
+ */
+static void ufs_change_blocknr(struct inode *inode, unsigned int beg,
+ unsigned int count, unsigned int oldb,
+ unsigned int newb, struct page *locked_page)
+{
+ const unsigned mask = (1 << (PAGE_CACHE_SHIFT - inode->i_blkbits)) - 1;
+ struct address_space * const mapping = inode->i_mapping;
+ pgoff_t index, cur_index;
+ unsigned end, pos, j;
+ struct page *page;
+ struct buffer_head *head, *bh;
+
+ UFSD("ENTER, ino %lu, count %u, oldb %u, newb %u\n",
+ inode->i_ino, count, oldb, newb);
+
+ BUG_ON(!locked_page);
+ BUG_ON(!PageLocked(locked_page));
+
+ cur_index = locked_page->index;
+
+ for (end = count + beg; beg < end; beg = (beg | mask) + 1) {
+ index = beg >> (PAGE_CACHE_SHIFT - inode->i_blkbits);
+
+ if (likely(cur_index != index)) {
+ page = ufs_get_locked_page(mapping, index);
+ if (!page || IS_ERR(page)) /* it was truncated or EIO */
+ continue;
+ } else
+ page = locked_page;
+
+ head = page_buffers(page);
+ bh = head;
+ pos = beg & mask;
+ for (j = 0; j < pos; ++j)
+ bh = bh->b_this_page;
+ j = 0;
+ do {
+ if (buffer_mapped(bh)) {
+ pos = bh->b_blocknr - oldb;
+ if (pos < count) {
+ UFSD(" change from %llu to %llu\n",
+ (unsigned long long)pos + oldb,
+ (unsigned long long)pos + newb);
+ bh->b_blocknr = newb + pos;
+ unmap_underlying_metadata(bh->b_bdev,
+ bh->b_blocknr);
+ mark_buffer_dirty(bh);
+ ++j;
+ }
+ }
+
+ bh = bh->b_this_page;
+ } while (bh != head);
+
+ if (j)
+ set_page_dirty(page);