[Devel] [PATCH RHEL8 COMMIT] ploop: Introduce zero_fill_pio()

[Konstantin Khorenko]

The commit is pushed to "branch-rh8-4.18.0-240.1.1.vz8.5.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh8-4.18.0-240.1.1.vz8.5.30
------>
commit 69ec92a1a309fef9642b390160a2385d03ab3c18
Author: Kirill Tkhai <ktkhai at virtuozzo.com>
Date:   Mon May 17 19:04:55 2021 +0300

    ploop: Introduce zero_fill_pio()
    
    Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
    
    =====================
    Patchset description:
    
    dm-ploop: Kill loop
    
    Intermediate patches can't be base for bisect.
    
    In scope of https://jira.sw.ru/browse/PSBM-123654
    
    Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
---
 drivers/md/dm-ploop-map.c | 23 +++++++++++++++++++++--
 1 file changed, 21 insertions(+), 2 deletions(-)

diff --git a/drivers/md/dm-ploop-map.c b/drivers/md/dm-ploop-map.c
index 5c2b4e32e525..ae7c1e0b4fc7 100644
--- a/drivers/md/dm-ploop-map.c
+++ b/drivers/md/dm-ploop-map.c
@@ -223,6 +223,26 @@ static int ploop_map_discard(struct ploop *ploop, struct pio *pio)
 	return DM_MAPIO_SUBMITTED;
 }
 
+/* Zero @count bytes of @qio->bi_io_vec since @from byte */
+static void zero_fill_pio(struct pio *pio)
+{
+	struct bvec_iter bi = {
+		.bi_size = pio->bi_iter.bi_size,
+		.bi_bvec_done = pio->bi_iter.bi_bvec_done,
+		.bi_idx = pio->bi_iter.bi_idx,
+	};
+	struct bio_vec bv;
+	void *data;
+
+	for_each_bvec(bv, pio->bi_io_vec, bi, bi) {
+		if (!bv.bv_len)
+			continue;
+		data = kmap(bv.bv_page);
+		memset(data + bv.bv_offset, 0, bv.bv_len);
+		kunmap(bv.bv_page);
+	}
+}
+
 struct pio *find_endio_hook_range(struct ploop *ploop, struct rb_root *root,
 				  unsigned int left, unsigned int right)
 {
@@ -988,9 +1008,8 @@ static void initiate_delta_read(struct ploop *ploop, unsigned int level,
 				unsigned int dst_cluster, struct pio *pio)
 {
 	if (dst_cluster == BAT_ENTRY_NONE) {
-		struct bio *bio = dm_bio_from_per_bio_data(pio, sizeof(*pio));
 		/* No one delta contains dst_cluster. */
-		zero_fill_bio(bio);
+		zero_fill_pio(pio);
 		pio_endio(pio);
 		return;
 	}