ext4: Fix the delalloc writepages to allocate blocks at the right offset.

When iterating through the pages which have mapped buffer_heads, we
failed to update the b_state value. This results in allocating blocks
at logical offset 0.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: stable@kernel.org

1 files changed, 39 insertions, 17 deletions

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index ac97348f85b5..c77a7ac753f3 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1653,35 +1653,39 @@ struct mpage_da_data {
  */
 static int mpage_da_submit_io(struct mpage_da_data *mpd)
 {
-        struct address_space *mapping = mpd->inode->i_mapping;
-        int ret = 0, err, nr_pages, i;
-        unsigned long index, end;
-        struct pagevec pvec;
         long pages_skipped;
+        struct pagevec pvec;
+        unsigned long index, end;
+        int ret = 0, err, nr_pages, i;
+        struct inode *inode = mpd->inode;
+        struct address_space *mapping = inode->i_mapping;
 
         BUG_ON(mpd->next_page <= mpd->first_page);
-        pagevec_init(&pvec, 0);
+        /*
+         * We need to start from the first_page to the next_page - 1
+         * to make sure we also write the mapped dirty buffer_heads.
+         * If we look at mpd->lbh.b_blocknr we would only be looking
+         * at the currently mapped buffer_heads.
+         */
         index = mpd->first_page;
         end = mpd->next_page - 1;
 
+        pagevec_init(&pvec, 0);
         while (index <= end) {
-                /*
-                 * We can use PAGECACHE_TAG_DIRTY lookup here because
-                 * even though we have cleared the dirty flag on the page
-                 * We still keep the page in the radix tree with tag
-                 * PAGECACHE_TAG_DIRTY. See clear_page_dirty_for_io.
-                 * The PAGECACHE_TAG_DIRTY is cleared in set_page_writeback
-                 * which is called via the below writepage callback.
-                 */
-                nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
-                                        PAGECACHE_TAG_DIRTY,
-                                        min(end - index,
-                                        (pgoff_t)PAGEVEC_SIZE-1) + 1);
+                nr_pages = pagevec_lookup(&pvec, mapping, index, PAGEVEC_SIZE);
                 if (nr_pages == 0)
                         break;
                 for (i = 0; i < nr_pages; i++) {
                         struct page *page = pvec.pages[i];
 
+                        index = page->index;
+                        if (index > end)
+                                break;
+                        index++;
+
+                        BUG_ON(!PageLocked(page));
+                        BUG_ON(PageWriteback(page));
+
                         pages_skipped = mpd->wbc->pages_skipped;
                         err = mapping->a_ops->writepage(page, mpd->wbc);
                         if (!err && (pages_skipped == mpd->wbc->pages_skipped))
@@ -2095,11 +2099,29 @@ static int __mpage_da_writepage(struct page *page,
                 bh = head;
                 do {
                         BUG_ON(buffer_locked(bh));
+                        /*
+                         * We need to try to allocate
+                         * unmapped blocks in the same page.
+                         * Otherwise we won't make progress
+                         * with the page in ext4_da_writepage
+                         */
                         if (buffer_dirty(bh) &&
                                 (!buffer_mapped(bh) || buffer_delay(bh))) {
                                 mpage_add_bh_to_extent(mpd, logical, bh);
                                 if (mpd->io_done)
                                         return MPAGE_DA_EXTENT_TAIL;
+                        } else if (buffer_dirty(bh) && (buffer_mapped(bh))) {
+                                /*
+                                 * mapped dirty buffer. We need to update
+                                 * the b_state because we look at
+                                 * b_state in mpage_da_map_blocks. We don't
+                                 * update b_size because if we find an
+                                 * unmapped buffer_head later we need to
+                                 * use the b_state flag of that buffer_head.
+                                 */
+                                if (mpd->lbh.b_size == 0)
+                                        mpd->lbh.b_state =
+                                                bh->b_state & BH_FLAGS;
                         }
                         logical++;
                 } while ((bh = bh->b_this_page) != head);