-/*
- * The idea of this helper function is following:
- * if prepare_write has allocated some blocks, but not all of them, the
- * transaction must include the content of the newly allocated blocks.
- * This content is expected to be set to zeroes by block_prepare_write().
- * 2006/10/14 SAW
- */
-static int ext3_prepare_failure(struct file *file, struct page *page,
- unsigned from, unsigned to)
-{
- struct address_space *mapping;
- struct buffer_head *bh, *head, *next;
- unsigned block_start, block_end;
- unsigned blocksize;
- int ret;
- handle_t *handle = ext3_journal_current_handle();
-
- mapping = page->mapping;
- if (ext3_should_writeback_data(mapping->host)) {
- /* optimization: no constraints about data */
-skip:
- return ext3_journal_stop(handle);
- }
-
- head = page_buffers(page);
- blocksize = head->b_size;
- for ( bh = head, block_start = 0;
- bh != head || !block_start;
- block_start = block_end, bh = next)
- {
- next = bh->b_this_page;
- block_end = block_start + blocksize;
- if (block_end <= from)
- continue;
- if (block_start >= to) {
- block_start = to;
- break;
- }
- if (!buffer_mapped(bh))
- /* prepare_write failed on this bh */
- break;
- if (ext3_should_journal_data(mapping->host)) {
- ret = do_journal_get_write_access(handle, bh);
- if (ret) {
- ext3_journal_stop(handle);
- return ret;
- }
- }
- /*
- * block_start here becomes the first block where the current iteration
- * of prepare_write failed.
- */
- }
- if (block_start <= from)
- goto skip;
-
- /* commit allocated and zeroed buffers */
- return mapping->a_ops->commit_write(file, page, from, block_start);
-}
-