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>

2 files changed, 38 insertions, 27 deletions

diff --git a/block/ll_rw_blk.c b/block/ll_rw_blk.c
index dfe0948ec8b2..b55ed0df33f0 100644
--- a/block/ll_rw_blk.c
+++ b/block/ll_rw_blk.c
@@ -527,22 +527,36 @@ int blk_do_ordered(struct request_queue *q, struct request **rqp)
         return 1;
 }
 
-static int ordered_bio_endio(struct request *rq, struct bio *bio,
-                             unsigned int nbytes, int error)
+static void req_bio_endio(struct request *rq, struct bio *bio,
+                          unsigned int nbytes, int error)
 {
         struct request_queue *q = rq->q;
 
-        if (&q->bar_rq != rq)
-                return 0;
+        if (&q->bar_rq != rq) {
+                if (error)
+                        clear_bit(BIO_UPTODATE, &bio->bi_flags);
+                else if (!test_bit(BIO_UPTODATE, &bio->bi_flags))
+                        error = -EIO;
 
-        /*
-         * Okay, this is the barrier request in progress, just
-         * record the error;
-         */
-        if (error && !q->orderr)
-                q->orderr = error;
+                if (unlikely(nbytes > bio->bi_size)) {
+                        printk("%s: want %u bytes done, only %u left\n",
+                               __FUNCTION__, nbytes, bio->bi_size);
+                        nbytes = bio->bi_size;
+                }
 
-        return 1;
+                bio->bi_size -= nbytes;
+                bio->bi_sector += (nbytes >> 9);
+                if (bio->bi_size == 0)
+                        bio_endio(bio, bio->bi_size, error);
+        } else {
+
+                /*
+                 * Okay, this is the barrier request in progress, just
+                 * record the error;
+                 */
+                if (error && !q->orderr)
+                        q->orderr = error;
+        }
 }
 
 /**
@@ -3388,8 +3402,7 @@ static int __end_that_request_first(struct request *req, int uptodate,
                 if (nr_bytes >= bio->bi_size) {
                         req->bio = bio->bi_next;
                         nbytes = bio->bi_size;
-                        if (!ordered_bio_endio(req, bio, nbytes, error))
-                                bio_endio(bio, nbytes, error);
+                        req_bio_endio(req, bio, nbytes, error);
                         next_idx = 0;
                         bio_nbytes = 0;
                 } else {
@@ -3444,8 +3457,7 @@ static int __end_that_request_first(struct request *req, int uptodate,
          * if the request wasn't completed, update state
          */
         if (bio_nbytes) {
-                if (!ordered_bio_endio(req, bio, bio_nbytes, error))
-                        bio_endio(bio, bio_nbytes, error);
+                req_bio_endio(req, bio, bio_nbytes, error);
                 bio->bi_idx += next_idx;
                 bio_iovec(bio)->bv_offset += nr_bytes;
                 bio_iovec(bio)->bv_len -= nr_bytes;
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);
 }