patch ext4-invalidate-pages-if-delalloc-block-allocation-fails.patch added to 2.6.27-stable tree

--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1821,6 +1821,39 @@  static inline void __unmap_underlying_bl
 		unmap_underlying_metadata(bdev, bh->b_blocknr + i);
 }
 
+static void ext4_da_block_invalidatepages(struct mpage_da_data *mpd,
+					sector_t logical, long blk_cnt)
+{
+	int nr_pages, i;
+	pgoff_t index, end;
+	struct pagevec pvec;
+	struct inode *inode = mpd->inode;
+	struct address_space *mapping = inode->i_mapping;
+
+	index = logical >> (PAGE_CACHE_SHIFT - inode->i_blkbits);
+	end   = (logical + blk_cnt - 1) >>
+				(PAGE_CACHE_SHIFT - inode->i_blkbits);
+	while (index <= end) {
+		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));
+			block_invalidatepage(page, 0);
+			ClearPageUptodate(page);
+			unlock_page(page);
+		}
+	}
+	return;
+}
+
 /*
  * mpage_da_map_blocks - go through given space
  *
@@ -1830,7 +1863,7 @@  static inline void __unmap_underlying_bl
  * The function skips space we know is already mapped to disk blocks.
  *
  */
-static void mpage_da_map_blocks(struct mpage_da_data *mpd)
+static int  mpage_da_map_blocks(struct mpage_da_data *mpd)
 {
 	int err = 0;
 	struct buffer_head *lbh = &mpd->lbh;
@@ -1841,7 +1874,7 @@  static void mpage_da_map_blocks(struct m
 	 * We consider only non-mapped and non-allocated blocks
 	 */
 	if (buffer_mapped(lbh) && !buffer_delay(lbh))
-		return;
+		return 0;
 
 	new.b_state = lbh->b_state;
 	new.b_blocknr = 0;
@@ -1852,10 +1885,38 @@  static void mpage_da_map_blocks(struct m
 	 * to write simply return
 	 */
 	if (!new.b_size)
-		return;
+		return 0;
 	err = mpd->get_block(mpd->inode, next, &new, 1);
-	if (err)
-		return;
+	if (err) {
+
+		/* If get block returns with error
+		 * we simply return. Later writepage
+		 * will redirty the page and writepages
+		 * will find the dirty page again
+		 */
+		if (err == -EAGAIN)
+			return 0;
+		/*
+		 * get block failure will cause us
+		 * to loop in writepages. Because
+		 * a_ops->writepage won't be able to
+		 * make progress. The page will be redirtied
+		 * by writepage and writepages will again
+		 * try to write the same.
+		 */
+		printk(KERN_EMERG "%s block allocation failed for inode %lu "
+				  "at logical offset %llu with max blocks "
+				  "%zd with error %d\n",
+				  __func__, mpd->inode->i_ino,
+				  (unsigned long long)next,
+				  lbh->b_size >> mpd->inode->i_blkbits, err);
+		printk(KERN_EMERG "This should not happen.!! "
+					"Data will be lost\n");
+		/* invlaidate all the pages */
+		ext4_da_block_invalidatepages(mpd, next,
+				lbh->b_size >> mpd->inode->i_blkbits);
+		return err;
+	}
 	BUG_ON(new.b_size == 0);
 
 	if (buffer_new(&new))
@@ -1868,7 +1929,7 @@  static void mpage_da_map_blocks(struct m
 	if (buffer_delay(lbh) || buffer_unwritten(lbh))
 		mpage_put_bnr_to_bhs(mpd, next, &new);
 
-	return;
+	return 0;
 }
 
 #define BH_FLAGS ((1 << BH_Uptodate) | (1 << BH_Mapped) | \
@@ -1937,8 +1998,8 @@  flush_it:
 	 * We couldn't merge the block to our extent, so we
 	 * need to flush current  extent and start new one
 	 */
-	mpage_da_map_blocks(mpd);
-	mpage_da_submit_io(mpd);
+	if (mpage_da_map_blocks(mpd) == 0)
+		mpage_da_submit_io(mpd);
 	mpd->io_done = 1;
 	return;
 }
@@ -1980,8 +2041,8 @@  static int __mpage_da_writepage(struct p
 		 * and start IO on them using writepage()
 		 */
 		if (mpd->next_page != mpd->first_page) {
-			mpage_da_map_blocks(mpd);
-			mpage_da_submit_io(mpd);
+			if (mpage_da_map_blocks(mpd) == 0)
+				mpage_da_submit_io(mpd);
 			/*
 			 * skip rest of the page in the page_vec
 			 */
@@ -2102,8 +2163,8 @@  static int mpage_da_writepages(struct ad
 	 * Handle last extent of pages
 	 */
 	if (!mpd.io_done && mpd.next_page != mpd.first_page) {
-		mpage_da_map_blocks(&mpd);
-		mpage_da_submit_io(&mpd);
+		if (mpage_da_map_blocks(&mpd) == 0)
+			mpage_da_submit_io(&mpd);
 	}
 
 	wbc->nr_to_write = to_write - mpd.pages_written;