[Devel] [PATCH RHEL7 COMMIT] ploop: zero blocks on reuse

[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.vz7.5.1
------>
commit 0bcaae57a549bf27c085db4bba6e10bce9fd4c55
Author: Andrey Smetanin <asmetanin at virtuozzo.com>
Date:   Tue May 19 08:27:08 2015 +0400

    ploop: zero blocks on reuse
    
    There is a check_zero feature allowing to skip zero writes if image-block
    is not allocated yet for given preq->req_cluster. But this means that inner-fs
    will hope to read zero from that range afterwards. Hence, while allocating
    the image-block we *must* zero it. We always do so in submit_alloc, but the
    implementation of free-block-reuse ended up in submit, not submit_alloc.
    
    https://jira.sw.ru/browse/PSBM-25391
    
    Signed-off-by: Maxim Patlasov <MPatlasov at parallels.com>
---
 drivers/block/ploop/dev.c | 33 ++++++++++++++++++++++++++++++---
 1 file changed, 30 insertions(+), 3 deletions(-)

diff --git a/drivers/block/ploop/dev.c b/drivers/block/ploop/dev.c
index 2e6302f..9aaab4a 100644
--- a/drivers/block/ploop/dev.c
+++ b/drivers/block/ploop/dev.c
@@ -2335,9 +2335,36 @@ restart:
 		preq->eng_state = PLOOP_E_DATA_WBI;
 		top_delta = ploop_top_delta(plo);
 		plo->st.bio_out++;
-		top_delta->io.ops->submit(&top_delta->io, preq, preq->req_rw,
-					  &preq->bl, preq->iblock,
-					  preq->req_size);
+		if (whole_block(plo, preq)) {
+			top_delta->io.ops->submit(&top_delta->io, preq, preq->req_rw,
+						  &preq->bl, preq->iblock,
+						  preq->req_size);
+		} else {
+			struct bio_list sbl;
+			struct bio * b;
+			int i;
+
+			if (!preq->aux_bio)
+				preq->aux_bio = bio_alloc(GFP_NOFS, block_vecs(plo));
+
+			if (!preq->aux_bio ||
+			    fill_bio(plo, preq->aux_bio, preq->req_cluster)) {
+				ploop_fail_immediate(preq, -ENOMEM);
+				break;
+			}
+
+			for (i = 0; i < preq->aux_bio->bi_vcnt; i++)
+				memset(page_address(preq->aux_bio->bi_io_vec[i].bv_page),
+				       0, PAGE_SIZE);
+
+			bio_list_for_each(b, &preq->bl) {
+				bio_bcopy(preq->aux_bio, b, plo);
+			}
+
+			sbl.head = sbl.tail = preq->aux_bio;
+			top_delta->io.ops->submit(&top_delta->io, preq, preq->req_rw,
+						  &sbl, preq->iblock, 1<<plo->cluster_log);
+		}
 		break;
 	}
 	case PLOOP_E_DELTA_ZERO_INDEX: