1 files changed, 85 insertions, 1 deletions
diff --git a/fs/nilfs2/page.c b/fs/nilfs2/page.c
index a6c3c2e817f..0c432416cfe 100644
--- a/fs/nilfs2/page.c
+++ b/fs/nilfs2/page.c
@@ -491,7 +491,7 @@ unsigned nilfs_page_count_clean_buffers(struct page *page,
 	}
 	return nc;
 }
- 
+
 void nilfs_mapping_init_once(struct address_space *mapping)
 {
 	memset(mapping, 0, sizeof(*mapping));
@@ -546,3 +546,87 @@ int __nilfs_clear_page_dirty(struct page *page)
 	}
 	return TestClearPageDirty(page);
 }
+
+/**
+ * nilfs_find_uncommitted_extent - find extent of uncommitted data
+ * @inode: inode
+ * @start_blk: start block offset (in)
+ * @blkoff: start offset of the found extent (out)
+ *
+ * This function searches an extent of buffers marked "delayed" which
+ * starts from a block offset equal to or larger than @start_blk.  If
+ * such an extent was found, this will store the start offset in
+ * @blkoff and return its length in blocks.  Otherwise, zero is
+ * returned.
+ */
+unsigned long nilfs_find_uncommitted_extent(struct inode *inode,
+					    sector_t start_blk,
+					    sector_t *blkoff)
+{
+	unsigned int i;
+	pgoff_t index;
+	unsigned int nblocks_in_page;
+	unsigned long length = 0;
+	sector_t b;
+	struct pagevec pvec;
+	struct page *page;
+
+	if (inode->i_mapping->nrpages == 0)
+		return 0;
+
+	index = start_blk >> (PAGE_CACHE_SHIFT - inode->i_blkbits);
+	nblocks_in_page = 1U << (PAGE_CACHE_SHIFT - inode->i_blkbits);
+
+	pagevec_init(&pvec, 0);
+
+repeat:
+	pvec.nr = find_get_pages_contig(inode->i_mapping, index, PAGEVEC_SIZE,
+					pvec.pages);
+	if (pvec.nr == 0)
+		return length;
+
+	if (length > 0 && pvec.pages[0]->index > index)
+		goto out;
+
+	b = pvec.pages[0]->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
+	i = 0;
+	do {
+		page = pvec.pages[i];
+
+		lock_page(page);
+		if (page_has_buffers(page)) {
+			struct buffer_head *bh, *head;
+
+			bh = head = page_buffers(page);
+			do {
+				if (b < start_blk)
+					continue;
+				if (buffer_delay(bh)) {
+					if (length == 0)
+						*blkoff = b;
+					length++;
+				} else if (length > 0) {
+					goto out_locked;
+				}
+			} while (++b, bh = bh->b_this_page, bh != head);
+		} else {
+			if (length > 0)
+				goto out_locked;
+
+			b += nblocks_in_page;
+		}
+		unlock_page(page);
+
+	} while (++i < pagevec_count(&pvec));
+
+	index = page->index + 1;
+	pagevec_release(&pvec);
+	cond_resched();
+	goto repeat;
+
+out_locked:
+	unlock_page(page);
+out:
+	pagevec_release(&pvec);
+	return length;
+}