linux-kernel - [PATCH] pblk: fix max

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Date:   Thu,  7 Mar 2019 13:18:53 +0100
From:   Javier González <javier@...igon.com>
To:     mb@...htnvm.io
Cc:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        Javier González <javier@...igon.com>
Subject: [PATCH] pblk: fix max_io calculation

When calculating the maximun I/O size allowed into the buffer, consider
the write size (ws_opt) used by the write thread in order to cover the
case in which, due to flushes, the mem and subm pointers are disaligned
by (ws_opt - 1). This case currently translates into a stall when
an I/O of the largest possible size is submitted.

Fixes: f9f9d1ae2c66 ("lightnvm: pblk: prevent stall due to wb threshold")

Signed-off-by: Javier González <javier@...igon.com>
---

Matias: Can you apply this as a fix to 5.1. This is a case I missed when fixing
the wb threshold, which is also scheduled for 5.1

Thanks,
Javier

 drivers/lightnvm/pblk-rl.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/lightnvm/pblk-rl.c b/drivers/lightnvm/pblk-rl.c
index b014957dde0b..a5f8bc2defbc 100644
--- a/drivers/lightnvm/pblk-rl.c
+++ b/drivers/lightnvm/pblk-rl.c
@@ -233,10 +233,15 @@ void pblk_rl_init(struct pblk_rl *rl, int budget, int threshold)
 	/* To start with, all buffer is available to user I/O writers */
 	rl->rb_budget = budget;
 	rl->rb_user_max = budget;
-	rl->rb_max_io = threshold ? (budget - threshold) : (budget - 1);
 	rl->rb_gc_max = 0;
 	rl->rb_state = PBLK_RL_HIGH;
 
+	/* Maximize I/O size and ansure that back threshold is respected */
+	if (threshold)
+		rl->rb_max_io = budget - pblk->min_write_pgs_data - threshold;
+	else
+		rl->rb_max_io = budget - pblk->min_write_pgs_data - 1;
+
 	atomic_set(&rl->rb_user_cnt, 0);
 	atomic_set(&rl->rb_gc_cnt, 0);
 	atomic_set(&rl->rb_space, -1);
-- 
2.17.1