as-iosched: fix write batch start point

New write batches currently start from where the last one completed.
We have no idea where the head is after switching batches, so this
makes little sense.  Instead, start the next batch from the request
with the earliest deadline in the hope that we avoid a deadline
expiry later on.

Signed-off-by: Aaron Carroll <aaronc@gelato.unsw.edu.au>
Acked-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/block/as-iosched.c b/block/as-iosched.c
index 4513fc59c9da..555cd6bf4ce5 100644
--- a/block/as-iosched.c
+++ b/block/as-iosched.c
@@ -1097,7 +1097,8 @@ dispatch_writes:
                 ad->batch_data_dir = REQ_ASYNC;
                 ad->current_write_count = ad->write_batch_count;
                 ad->write_batch_idled = 0;
-                rq = ad->next_rq[ad->batch_data_dir];
+                rq = rq_entry_fifo(ad->fifo_list[REQ_ASYNC].next);
+                ad->last_check_fifo[REQ_ASYNC] = jiffies;
                 goto dispatch_request;
         }