jfs: Fix error handling in metapage_writepage()

Improved error handling so that last_write_complete(), and thus
end_page_writeback(), gets called only once.
Signed-off-by: NDave Kleikamp <shaggy@linux.vnet.ibm.com>
Reported-by: NEric Sesterhenn <snakebyte@gmx.de>

fs/jfs/jfs_metapage.c

@@ -369,6 +369,7 @@ static int metapage_writepage(struct page *page, struct writeback_control *wbc)
 	unsigned long bio_bytes = 0;
 	unsigned long bio_offset = 0;
 	int offset;
+	int bad_blocks = 0;
 
 	page_start = (sector_t)page->index <<
 		     (PAGE_CACHE_SHIFT - inode->i_blkbits);
@@ -394,6 +395,7 @@ static int metapage_writepage(struct page *page, struct writeback_control *wbc)
 		}
 
 		clear_bit(META_dirty, &mp->flag);
+		set_bit(META_io, &mp->flag);
 		block_offset = offset >> inode->i_blkbits;
 		lblock = page_start + block_offset;
 		if (bio) {
@@ -402,7 +404,6 @@ static int metapage_writepage(struct page *page, struct writeback_control *wbc)
 				len = min(xlen, blocks_per_mp);
 				xlen -= len;
 				bio_bytes += len << inode->i_blkbits;
-				set_bit(META_io, &mp->flag);
 				continue;
 			}
 			/* Not contiguous */
@@ -424,12 +425,14 @@ static int metapage_writepage(struct page *page, struct writeback_control *wbc)
 		xlen = (PAGE_CACHE_SIZE - offset) >> inode->i_blkbits;
 		pblock = metapage_get_blocks(inode, lblock, &xlen);
 		if (!pblock) {
-			/* Need better error handling */
 			printk(KERN_ERR "JFS: metapage_get_blocks failed\n");
-			dec_io(page, last_write_complete);
+			/*
+			 * We already called inc_io(), but can't cancel it
+			 * with dec_io() until we're done with the page
+			 */
+			bad_blocks++;
 			continue;
 		}
-		set_bit(META_io, &mp->flag);
 		len = min(xlen, (int)JFS_SBI(inode->i_sb)->nbperpage);
 
 		bio = bio_alloc(GFP_NOFS, 1);
@@ -459,6 +462,9 @@ static int metapage_writepage(struct page *page, struct writeback_control *wbc)
 
 	unlock_page(page);
 
+	if (bad_blocks)
+		goto err_out;
+
 	if (nr_underway == 0)
 		end_page_writeback(page);
 
@@ -474,7 +480,9 @@ static int metapage_writepage(struct page *page, struct writeback_control *wbc)
 	bio_put(bio);
 	unlock_page(page);
 	dec_io(page, last_write_complete);
-
+err_out:
+	while (bad_blocks--)
+		dec_io(page, last_write_complete);
 	return -EIO;
 }