[Devel] [PATCH RHEL7 COMMIT] ploop: pio_nfs does not require PLOOP_REQ_ISSUE_FLUSH (v2)

[Konstantin Khorenko]

The commit is pushed to "branch-rh7-3.10.0-327.36.1.vz7.20.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-327.36.1.vz7.20.11
------>
commit cc3748db2c17d5805d9568d774cfe63b41195258
Author: Maxim Patlasov <mpatlasov at virtuozzo.com>
Date:   Tue Dec 6 15:48:22 2016 +0400

    ploop: pio_nfs does not require PLOOP_REQ_ISSUE_FLUSH (v2)
    
    The flag was introduced for local case: if we modify local
    block-device directly, bypassing ext4, we cannot rely on
    fsync() and must flush the device explicitly. It is not the
    case for pio_nfs, so it's not necessary to set
    PLOOP_REQ_ISSUE_FLUSH.
    
    The patch is important because pio_nfs doesn't provide
    issue_flush method.
    
    Changed in v2:
     - rebase: after 34c7bf1755 moved set_bit and nullifying submit into
       ploop_entry_nullify_req(), the patch to be applied to this new
       place.
    
    Signed-off-by: Maxim Patlasov <mpatlasov at virtuozzo.com>
---
 drivers/block/ploop/dev.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/block/ploop/dev.c b/drivers/block/ploop/dev.c
index 5aacd2a..eaf48c2 100644
--- a/drivers/block/ploop/dev.c
+++ b/drivers/block/ploop/dev.c
@@ -2037,9 +2037,11 @@ ploop_entry_nullify_req(struct ploop_request *preq)
 	 * (see dio_submit()). So fsync of EXT4 image doesnt help us.
 	 * We need to force sync of nullified blocks.
 	 */
+	if (top_delta->io.ops->issue_flush) {
+		preq->eng_io = &top_delta->io;
+		set_bit(PLOOP_REQ_ISSUE_FLUSH, &preq->state);
+	}
 
-	preq->eng_io = &top_delta->io;
-	set_bit(PLOOP_REQ_ISSUE_FLUSH, &preq->state);
 	top_delta->io.ops->submit(&top_delta->io, preq, preq->req_rw,
 				  &sbl, preq->iblock, 1<<plo->cluster_log);
 	return 0;