+/* IO operations when bitmap is stored near all superblocks */
+static struct page *read_sb_page(mddev_t *mddev, long offset, unsigned long index)
+{
+ /* choose a good rdev and read the page from there */
+
+ mdk_rdev_t *rdev;
+ struct list_head *tmp;
+ struct page *page = alloc_page(GFP_KERNEL);
+ sector_t target;
+
+ if (!page)
+ return ERR_PTR(-ENOMEM);
+ do {
+ ITERATE_RDEV(mddev, rdev, tmp)
+ if (rdev->in_sync && !rdev->faulty)
+ goto found;
+ return ERR_PTR(-EIO);
+
+ found:
+ target = (rdev->sb_offset << 1) + offset + index * (PAGE_SIZE/512);
+
+ } while (!sync_page_io(rdev->bdev, target, PAGE_SIZE, page, READ));
+
+ page->index = index;
+ return page;
+}
+
+static int write_sb_page(mddev_t *mddev, long offset, struct page *page, int wait)
+{
+ mdk_rdev_t *rdev;
+ struct list_head *tmp;
+
+ ITERATE_RDEV(mddev, rdev, tmp)
+ if (rdev->in_sync && !rdev->faulty)
+ md_super_write(mddev, rdev,
+ (rdev->sb_offset<<1) + offset
+ + page->index * (PAGE_SIZE/512),
+ PAGE_SIZE,
+ page);
+
+ if (wait)
+ wait_event(mddev->sb_wait, atomic_read(&mddev->pending_writes)==0);
+ return 0;
+}
+