1 files changed, 84 insertions, 0 deletions

diff --git a/fs/nilfs2/page.c b/fs/nilfs2/page.c
index a6c3c2e817f8..48a775ec1d2a 100644
--- a/fs/nilfs2/page.c
+++ b/fs/nilfs2/page.c
@@ -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;
+}