ext4: note the error in ext4_end_bio()

ext4_end_bio() currently throws away the error that it receives.  Chances
are this is part of a spate of errors, one of which will end up getting
the error returned to userspace somehow, but we shouldn't take that risk.
Also print out the errno to aid in debug.
Signed-off-by: Matthew Wilcox <matthew.r.wilcox@intel.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: stable@vger.kernel.org

fs/ext4/page-io.c

@@ -308,13 +308,14 @@ static void ext4_end_bio(struct bio *bio, int error)
 	if (error) {
 		struct inode *inode = io_end->inode;
 
-		ext4_warning(inode->i_sb, "I/O error writing to inode %lu "
+		ext4_warning(inode->i_sb, "I/O error %d writing to inode %lu "
 			     "(offset %llu size %ld starting block %llu)",
-			     inode->i_ino,
+			     error, inode->i_ino,
 			     (unsigned long long) io_end->offset,
 			     (long) io_end->size,
 			     (unsigned long long)
 			     bi_sector >> (inode->i_blkbits - 9));
+		mapping_set_error(inode->i_mapping, error);
 	}
 
 	if (io_end->flag & EXT4_IO_END_UNWRITTEN) {