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From:   hans@owltronix.com
To:     Matias Bjorling <mb@lightnvm.io>
Cc:     javier@javigon.com, Zhoujie Wu <zjwu@marvell.com>,
        linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
        Hans Holmberg <hans.holmberg@cnexlabs.com>
Subject: [PATCH] lightnvm: pblk: extend line wp balance check
Date:   Tue, 29 Jan 2019 09:47:37 +0100
Message-Id: <20190129084737.718-1-hans@owltronix.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

From: Hans Holmberg <hans.holmberg@cnexlabs.com>

pblk stripes writes of minimal write size across all non-offline chunks
in a line, which means that the maximum write pointer delta should not
exceed the minimal write size. Extend the line write pointer balance check
to cover this case.

Signed-off-by: Hans Holmberg <hans.holmberg@cnexlabs.com>
---

This patch applies on top of Zhoujie's V3 of 
"lightnvm: pblk: ignore bad block wp for pblk_line_wp_is_unbalanced

 drivers/lightnvm/pblk-recovery.c | 60 ++++++++++++++++++++------------
 1 file changed, 37 insertions(+), 23 deletions(-)

diff --git a/drivers/lightnvm/pblk-recovery.c b/drivers/lightnvm/pblk-recovery.c
index 02d466e6925e..d86f580036d3 100644
--- a/drivers/lightnvm/pblk-recovery.c
+++ b/drivers/lightnvm/pblk-recovery.c
@@ -302,41 +302,55 @@ static int pblk_pad_distance(struct pblk *pblk, struct pblk_line *line)
 	return (distance > line->left_msecs) ? line->left_msecs : distance;
 }
 
-static int pblk_line_wp_is_unbalanced(struct pblk *pblk,
-				      struct pblk_line *line)
+/* Return a chunk belonging to a line by stripe(write order) index */
+static struct nvm_chk_meta *pblk_get_stripe_chunk(struct pblk *pblk,
+						  struct pblk_line *line,
+						  int index)
 {
 	struct nvm_tgt_dev *dev = pblk->dev;
 	struct nvm_geo *geo = &dev->geo;
-	struct pblk_line_meta *lm = &pblk->lm;
 	struct pblk_lun *rlun;
-	struct nvm_chk_meta *chunk;
 	struct ppa_addr ppa;
-	u64 line_wp;
-	int pos, i, bit;
+	int pos;
 
-	bit = find_first_zero_bit(line->blk_bitmap, lm->blk_per_line);
-	if (bit >= lm->blk_per_line)
-		return 0;
-	rlun = &pblk->luns[bit];
+	rlun = &pblk->luns[index];
 	ppa = rlun->bppa;
 	pos = pblk_ppa_to_pos(geo, ppa);
-	chunk = &line->chks[pos];
 
-	line_wp = chunk->wp;
+	return &line->chks[pos];
+}
 
-	for (i = bit + 1; i < lm->blk_per_line; i++) {
-		rlun = &pblk->luns[i];
-		ppa = rlun->bppa;
-		pos = pblk_ppa_to_pos(geo, ppa);
-		chunk = &line->chks[pos];
+static int pblk_line_wps_are_unbalanced(struct pblk *pblk,
+				      struct pblk_line *line)
+{
+	struct pblk_line_meta *lm = &pblk->lm;
+	int blk_in_line = lm->blk_per_line;
+	struct nvm_chk_meta *chunk;
+	u64 max_wp, min_wp;
+	int i;
 
-		if (chunk->state & NVM_CHK_ST_OFFLINE)
-			continue;
+	i = find_first_zero_bit(line->blk_bitmap, blk_in_line);
+
+	/* If there is one or zero good chunks in the line,
+	 * the write pointers can't be unbalanced.
+	 */
+	if (i >= (blk_in_line - 1))
+		return 0;
 
-		if (chunk->wp > line_wp)
+	chunk = pblk_get_stripe_chunk(pblk, line, i);
+	max_wp = chunk->wp;
+	if (max_wp > pblk->max_write_pgs)
+		min_wp = max_wp - pblk->max_write_pgs;
+	else
+		min_wp = 0;
+
+	i = find_next_zero_bit(line->blk_bitmap, blk_in_line, i + 1);
+	while (i < blk_in_line) {
+		chunk = pblk_get_stripe_chunk(pblk, line, i);
+		if (chunk->wp > max_wp || chunk->wp < min_wp)
 			return 1;
-		else if (chunk->wp < line_wp)
-			line_wp = chunk->wp;
+
+		i = find_next_zero_bit(line->blk_bitmap, blk_in_line, i + 1);
 	}
 
 	return 0;
@@ -362,7 +376,7 @@ static int pblk_recov_scan_oob(struct pblk *pblk, struct pblk_line *line,
 	int ret;
 	u64 left_ppas = pblk_sec_in_open_line(pblk, line) - lm->smeta_sec;
 
-	if (pblk_line_wp_is_unbalanced(pblk, line))
+	if (pblk_line_wps_are_unbalanced(pblk, line))
 		pblk_warn(pblk, "recovering unbalanced line (%d)\n", line->id);
 
 	ppa_list = p.ppa_list;
-- 
2.17.1