lightnvm: pblk: kick writer on new flush points

Unless we kick the writer directly when setting a new flush point, the
user risks having to wait for up to one second (the default timeout for
the write thread to be kicked) for the IO to complete.
Signed-off-by: Hans Holmberg <hans.holmberg@cnexlabs.com>
Signed-off-by: Matias Bjørling <mb@lightnvm.io>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/lightnvm/pblk-cache.c

@@ -44,13 +44,15 @@ int pblk_write_to_cache(struct pblk *pblk, struct bio *bio, unsigned long flags)
 		goto out;
 	}
 
-	if (unlikely(!bio_has_data(bio)))
-		goto out;
-
 	pblk_ppa_set_empty(&w_ctx.ppa);
 	w_ctx.flags = flags;
-	if (bio->bi_opf & REQ_PREFLUSH)
+	if (bio->bi_opf & REQ_PREFLUSH) {
 		w_ctx.flags |= PBLK_FLUSH_ENTRY;
+		pblk_write_kick(pblk);
+	}
+
+	if (unlikely(!bio_has_data(bio)))
+		goto out;
 
 	for (i = 0; i < nr_entries; i++) {
 		void *data = bio_data(bio);

drivers/lightnvm/pblk-core.c

@@ -322,7 +322,7 @@ int pblk_bio_add_pages(struct pblk *pblk, struct bio *bio, gfp_t flags,
 	return -1;
 }
 
-static void pblk_write_kick(struct pblk *pblk)
+void pblk_write_kick(struct pblk *pblk)
 {
 	wake_up_process(pblk->writer_ts);
 	mod_timer(&pblk->wtimer, jiffies + msecs_to_jiffies(1000));

drivers/lightnvm/pblk-rb.c

@@ -419,7 +419,7 @@ void pblk_rb_flush(struct pblk_rb *rb)
 	if (pblk_rb_flush_point_set(rb, NULL, mem))
 		return;
 
-	pblk_write_should_kick(pblk);
+	pblk_write_kick(pblk);
 }
 
 static int pblk_rb_may_write_flush(struct pblk_rb *rb, unsigned int nr_entries,

drivers/lightnvm/pblk.h

@@ -851,6 +851,7 @@ void pblk_map_rq(struct pblk *pblk, struct nvm_rq *rqd, unsigned int sentry,
 int pblk_write_ts(void *data);
 void pblk_write_timer_fn(struct timer_list *t);
 void pblk_write_should_kick(struct pblk *pblk);
+void pblk_write_kick(struct pblk *pblk);
 
 /*
  * pblk read path