+ page_zero_new_buffers(page, start+copied, start+len);
+ }
+ flush_dcache_page(page);
+
+ /* This could be a short (even 0-length) commit */
+ __block_commit_write(inode, page, start, start+copied);
+
+ return copied;
+}
+EXPORT_SYMBOL(block_write_end);
+
+int generic_write_end(struct file *file, struct address_space *mapping,
+ loff_t pos, unsigned len, unsigned copied,
+ struct page *page, void *fsdata)
+{
+ struct inode *inode = mapping->host;
+ int i_size_changed = 0;
+
+ copied = block_write_end(file, mapping, pos, len, copied, page, fsdata);
+
+ /*
+ * No need to use i_size_read() here, the i_size
+ * cannot change under us because we hold i_mutex.
+ *
+ * But it's important to update i_size while still holding page lock:
+ * page writeout could otherwise come in and zero beyond i_size.
+ */
+ if (pos+copied > inode->i_size) {
+ i_size_write(inode, pos+copied);
+ i_size_changed = 1;
+ }
+
+ unlock_page(page);
+ page_cache_release(page);
+
+ /*
+ * Don't mark the inode dirty under page lock. First, it unnecessarily
+ * makes the holding time of page lock longer. Second, it forces lock
+ * ordering of page lock and transaction start for journaling
+ * filesystems.
+ */
+ if (i_size_changed)
+ mark_inode_dirty(inode);
+
+ return copied;
+}
+EXPORT_SYMBOL(generic_write_end);
+
+/*
+ * block_is_partially_uptodate checks whether buffers within a page are
+ * uptodate or not.
+ *
+ * Returns true if all buffers which correspond to a file portion
+ * we want to read are uptodate.
+ */
+int block_is_partially_uptodate(struct page *page, read_descriptor_t *desc,
+ unsigned long from)
+{
+ struct inode *inode = page->mapping->host;
+ unsigned block_start, block_end, blocksize;
+ unsigned to;
+ struct buffer_head *bh, *head;
+ int ret = 1;
+
+ if (!page_has_buffers(page))
+ return 0;
+
+ blocksize = 1 << inode->i_blkbits;
+ to = min_t(unsigned, PAGE_CACHE_SIZE - from, desc->count);
+ to = from + to;
+ if (from < blocksize && to > PAGE_CACHE_SIZE - blocksize)
+ return 0;
+
+ head = page_buffers(page);
+ bh = head;
+ block_start = 0;
+ do {
+ block_end = block_start + blocksize;
+ if (block_end > from && block_start < to) {
+ if (!buffer_uptodate(bh)) {
+ ret = 0;
+ break;
+ }
+ if (block_end >= to)
+ break;
+ }
+ block_start = block_end;
+ bh = bh->b_this_page;
+ } while (bh != head);
+
+ return ret;
+}
+EXPORT_SYMBOL(block_is_partially_uptodate);
+
+/*
+ * Generic "read page" function for block devices that have the normal
+ * get_block functionality. This is most of the block device filesystems.
+ * Reads the page asynchronously --- the unlock_buffer() and
+ * set/clear_buffer_uptodate() functions propagate buffer state into the
+ * page struct once IO has completed.
+ */
+int block_read_full_page(struct page *page, get_block_t *get_block)
+{
+ struct inode *inode = page->mapping->host;
+ sector_t iblock, lblock;
+ struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
+ unsigned int blocksize;
+ int nr, i;
+ int fully_mapped = 1;
+
+ BUG_ON(!PageLocked(page));
+ blocksize = 1 << inode->i_blkbits;
+ if (!page_has_buffers(page))
+ create_empty_buffers(page, blocksize, 0);
+ head = page_buffers(page);
+
+ iblock = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
+ lblock = (i_size_read(inode)+blocksize-1) >> inode->i_blkbits;
+ bh = head;
+ nr = 0;
+ i = 0;
+
+ do {
+ if (buffer_uptodate(bh))
+ continue;
+
+ if (!buffer_mapped(bh)) {
+ int err = 0;
+
+ fully_mapped = 0;
+ if (iblock < lblock) {
+ WARN_ON(bh->b_size != blocksize);
+ err = get_block(inode, iblock, bh, 0);
+ if (err)
+ SetPageError(page);
+ }
+ if (!buffer_mapped(bh)) {
+ zero_user(page, i * blocksize, blocksize);
+ if (!err)
+ set_buffer_uptodate(bh);
+ continue;
+ }
+ /*
+ * get_block() might have updated the buffer
+ * synchronously
+ */
+ if (buffer_uptodate(bh))
+ continue;
+ }
+ arr[nr++] = bh;
+ } while (i++, iblock++, (bh = bh->b_this_page) != head);
+
+ if (fully_mapped)
+ SetPageMappedToDisk(page);
+
+ if (!nr) {
+ /*
+ * All buffers are uptodate - we can set the page uptodate
+ * as well. But not if get_block() returned an error.
+ */
+ if (!PageError(page))
+ SetPageUptodate(page);
+ unlock_page(page);
+ return 0;
+ }
+
+ /* Stage two: lock the buffers */
+ for (i = 0; i < nr; i++) {
+ bh = arr[i];
+ lock_buffer(bh);
+ mark_buffer_async_read(bh);