Only call bi_end_io once for any bio

Currently bi_end_io can be called multiple times as sub-requests
complete.  However no ->bi_end_io function wants to know about that.
So only call when the bio is complete.
Signed-off-by: Neil Brown <neilb@suse.de>

### Diffstat output
 ./fs/bio.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff .prev/fs/bio.c ./fs/bio.c
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

fs/bio.c

@@ -1018,6 +1018,8 @@ void bio_endio(struct bio *bio, unsigned int bytes_done, int error)
 {
 	if (error)
 		clear_bit(BIO_UPTODATE, &bio->bi_flags);
+	else if (!test_bit(BIO_UPTODATE, &bio->bi_flags))
+		error = -EIO;
 
 	if (unlikely(bytes_done > bio->bi_size)) {
 		printk("%s: want %u bytes done, only %u left\n", __FUNCTION__,
@@ -1028,7 +1030,7 @@ void bio_endio(struct bio *bio, unsigned int bytes_done, int error)
 	bio->bi_size -= bytes_done;
 	bio->bi_sector += (bytes_done >> 9);
 
-	if (bio->bi_end_io)
+	if (bio->bi_size && bio->bi_end_io)
 		bio->bi_end_io(bio, bytes_done, error);
 }