[Devel] [PATCH RHEL7 COMMIT] Revert "ploop: fix busyloop on secondary discard bio"

[Konstantin Khorenko]

The commit is pushed to "branch-rh7-3.10.0-123.1.2-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-123.1.2.vz7.5.4
------>
commit 01cebd23c8c37738f3d3d5a2aec2a68e8fe74a15
Author: Konstantin Khorenko <khorenko at openvz.org>
Date:   Wed May 20 15:53:18 2015 +0400

    Revert "ploop: fix busyloop on secondary discard bio"
    
    This reverts commit a5678140dd8f793272b5e562e81e27e2a249e4fd.
    
    This patch causes mkfs.ext4 hangs during ploop init =>
    roll it back until we have proper fix.
    
    https://jira.sw.ru/browse/PSBM-33633
    
    Signed-off-by: Andrey Smetanin <asmetanin at virtuozzo.com>
---
 drivers/block/ploop/dev.c      |  9 ++-------
 drivers/block/ploop/freeblks.c | 12 ++++--------
 2 files changed, 6 insertions(+), 15 deletions(-)

diff --git a/drivers/block/ploop/dev.c b/drivers/block/ploop/dev.c
index f780618..ca6333a 100644
--- a/drivers/block/ploop/dev.c
+++ b/drivers/block/ploop/dev.c
@@ -551,11 +551,7 @@ ploop_bio_queue(struct ploop_device * plo, struct bio * bio,
 
 	__TRACE("A %p %u\n", preq, preq->req_cluster);
 
-	if (unlikely(bio->bi_rw & REQ_DISCARD))
-		plo->bio_discard_qlen--;
-	else
-		plo->bio_qlen--;
-
+	plo->bio_qlen--;
 	ploop_entry_add(plo, preq);
 
 	if (bio->bi_size && !(bio->bi_rw & REQ_DISCARD))
@@ -2576,8 +2572,7 @@ static void ploop_wait(struct ploop_device * plo, int once, struct blk_plug *plu
 			     !plo->active_reqs))
 				break;
 		} else if (plo->bio_head ||
-				(!bio_list_empty(&plo->bio_discard_list) &&
-				 !ploop_discard_is_inprogress(plo->fbd))) {
+				!bio_list_empty(&plo->bio_discard_list)) {
 			/* ready_queue and entry_queue are empty, but
 			 * bio list not. Obviously, we'd like to process
 			 * bio_list instead of sleeping */
diff --git a/drivers/block/ploop/freeblks.c b/drivers/block/ploop/freeblks.c
index 89108c7..cf48d3a 100644
--- a/drivers/block/ploop/freeblks.c
+++ b/drivers/block/ploop/freeblks.c
@@ -696,24 +696,20 @@ int ploop_fb_get_free_block(struct ploop_freeblks_desc *fbd,
 
 static void fbd_complete_bio(struct ploop_freeblks_desc *fbd, int err)
 {
-	struct ploop_device *plo = fbd->plo;
 	unsigned int nr_completed = 0;
 
 	while (fbd->fbd_dbl.head) {
 		struct bio * bio = fbd->fbd_dbl.head;
 		fbd->fbd_dbl.head = bio->bi_next;
 		bio->bi_next = NULL;
-		BIO_ENDIO(plo->queue, bio, err);
+		BIO_ENDIO(fbd->plo->queue, bio, err);
 		nr_completed++;
 	}
 	fbd->fbd_dbl.tail = NULL;
 
-	spin_lock_irq(&plo->lock);
-	plo->bio_total -= nr_completed;
-	if (!bio_list_empty(&plo->bio_discard_list) &&
-	    waitqueue_active(&plo->waitq))
-		wake_up_interruptible(&plo->waitq);
-	spin_unlock_irq(&plo->lock);
+	spin_lock_irq(&fbd->plo->lock);
+	fbd->plo->bio_total -= nr_completed;
+	spin_unlock_irq(&fbd->plo->lock);
 }
 
 void ploop_fb_reinit(struct ploop_freeblks_desc *fbd, int err)