Don't decrement bi_size in bio_endio

The only caller of bio_endio that does not pass the full bi_size
is end_that_request_first.  Also, no ->bi_end_io method is really
interested in bi_size being decremented.

So move the decrement and related code into ll_rw_blk and merge it
with order_bio_endio to form req_bio_endio which does endio functionality
specific to request completion.

As some ->bi_end_io methods do check bi_size of 0, we set it thus for
now, but that will go in the next patch.

Signed-off-by: Neil Brown <neilb@suse.de>

### Diffstat output
 ./block/ll_rw_blk.c |   42 +++++++++++++++++++++++++++---------------
 ./fs/bio.c          |   23 +++++++++++------------
 2 files changed, 38 insertions(+), 27 deletions(-)

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

1 files changed, 11 insertions, 12 deletions

diff --git a/fs/bio.c b/fs/bio.c
index 5720b940bb5f..3adecd64ff6e 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -1006,13 +1006,14 @@ void bio_check_pages_dirty(struct bio *bio)
  * @error:      error, if any
  *
  * Description:
- *   bio_endio() will end I/O on @bytes_done number of bytes. This may be
- *   just a partial part of the bio, or it may be the whole bio. bio_endio()
- *   is the preferred way to end I/O on a bio, it takes care of decrementing
- *   bi_size and clearing BIO_UPTODATE on error. @error is 0 on success, and
- *   and one of the established -Exxxx (-EIO, for instance) error values in
- *   case something went wrong. Noone should call bi_end_io() directly on
- *   a bio unless they own it and thus know that it has an end_io function.
+ *   bio_endio() will end I/O on @bytes_done number of bytes. This
+ *   must always be the whole (remaining) bio. bio_endio() is the
+ *   preferred way to end I/O on a bio, it takes care of clearing
+ *   BIO_UPTODATE on error. @error is 0 on success, and and one of the
+ *   established -Exxxx (-EIO, for instance) error values in case
+ *   something went wrong. Noone should call bi_end_io() directly on a
+ *   bio unless they own it and thus know that it has an end_io
+ *   function.
  **/
 void bio_endio(struct bio *bio, unsigned int bytes_done, int error)
 {
@@ -1021,16 +1022,14 @@ void bio_endio(struct bio *bio, unsigned int bytes_done, int error)
         else if (!test_bit(BIO_UPTODATE, &bio->bi_flags))
                 error = -EIO;
 
-        if (unlikely(bytes_done > bio->bi_size)) {
+        if (unlikely(bytes_done != bio->bi_size)) {
                 printk("%s: want %u bytes done, only %u left\n", __FUNCTION__,
                                                 bytes_done, bio->bi_size);
                 bytes_done = bio->bi_size;
         }
 
-        bio->bi_size -= bytes_done;
-        bio->bi_sector += (bytes_done >> 9);
-
-        if (bio->bi_size && bio->bi_end_io)
+        bio->bi_size = 0; /* expected by some callees - will be removed */
+        if (bio->bi_end_io)
                 bio->bi_end_io(bio, bytes_done, error);
 }