linux-kernel - [PATCH AUTOSEL 4.18 014/126] lightnvm: pblk: fix race condition on metadata I/O

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Message-Id: <20181031230754.29029-14-sashal@kernel.org>
Date:   Wed, 31 Oct 2018 19:06:02 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     stable@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Javier González <javier@...igon.com>,
        Javier González <javier@...xlabs.com>,
        Matias Bjørling <mb@...htnvm.io>,
        Jens Axboe <axboe@...nel.dk>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH AUTOSEL 4.18 014/126] lightnvm: pblk: fix race condition on metadata I/O

From: Javier González <javier@...igon.com>

[ Upstream commit d8adaa3b86324c6186d0adf74bc256bdacfffdb6 ]

In pblk, when a new line is allocated, metadata for the previously
written line is scheduled. This is done through a fixed memory region
that is shared through time and contexts across different lines and
therefore protected by a lock. Unfortunately, this lock is not properly
covering all the metadata used for sharing this memory regions,
resulting in a race condition.

This patch fixes this race condition by protecting this metadata
properly.

Fixes: dd2a43437337 ("lightnvm: pblk: sched. metadata on write thread")
Signed-off-by: Javier González <javier@...xlabs.com>
Signed-off-by: Matias Bjørling <mb@...htnvm.io>
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/lightnvm/pblk-write.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/drivers/lightnvm/pblk-write.c b/drivers/lightnvm/pblk-write.c
index f353e52941f5..89ac60d4849e 100644
--- a/drivers/lightnvm/pblk-write.c
+++ b/drivers/lightnvm/pblk-write.c
@@ -417,12 +417,11 @@ int pblk_submit_meta_io(struct pblk *pblk, struct pblk_line *meta_line)
 			rqd->ppa_list[i] = addr_to_gen_ppa(pblk, paddr, id);
 	}
 
+	spin_lock(&l_mg->close_lock);
 	emeta->mem += rq_len;
-	if (emeta->mem >= lm->emeta_len[0]) {
-		spin_lock(&l_mg->close_lock);
+	if (emeta->mem >= lm->emeta_len[0])
 		list_del(&meta_line->list);
-		spin_unlock(&l_mg->close_lock);
-	}
+	spin_unlock(&l_mg->close_lock);
 
 	pblk_down_page(pblk, rqd->ppa_list, rqd->nr_ppas);
 
@@ -491,14 +490,15 @@ static struct pblk_line *pblk_should_submit_meta_io(struct pblk *pblk,
 	struct pblk_line *meta_line;
 
 	spin_lock(&l_mg->close_lock);
-retry:
 	if (list_empty(&l_mg->emeta_list)) {
 		spin_unlock(&l_mg->close_lock);
 		return NULL;
 	}
 	meta_line = list_first_entry(&l_mg->emeta_list, struct pblk_line, list);
-	if (meta_line->emeta->mem >= lm->emeta_len[0])
-		goto retry;
+	if (meta_line->emeta->mem >= lm->emeta_len[0]) {
+		spin_unlock(&l_mg->close_lock);
+		return NULL;
+	}
 	spin_unlock(&l_mg->close_lock);
 
 	if (!pblk_valid_meta_ppa(pblk, meta_line, data_rqd))
-- 
2.17.1