linux-kernel - [GIT PULL 06/26] lightnvm: pblk: fix race during put line

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Message-Id: <20190504183811.18725-7-mb@lightnvm.io>
Date:   Sat,  4 May 2019 20:37:51 +0200
From:   Matias Bjørling <mb@...htnvm.io>
To:     axboe@...com
Cc:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        Igor Konopko <igor.j.konopko@...el.com>,
        Matias Bjørling <mb@...htnvm.io>
Subject: [GIT PULL 06/26] lightnvm: pblk: fix race during put line

From: Igor Konopko <igor.j.konopko@...el.com>

In the pblk_put_line_back function, a race condition with
__pblk_map_invalidate can make a line not part of any lists.

Fix gc_list by resetting it to null fixes the above issue.

Fixes: a4bd217 ("lightnvm: physical block device (pblk) target")
Signed-off-by: Igor Konopko <igor.j.konopko@...el.com>
Reviewed-by: Javier González <javier@...igon.com>
Reviewed-by: Hans Holmberg <hans.holmberg@...xlabs.com>
Signed-off-by: Matias Bjørling <mb@...htnvm.io>
---
 drivers/lightnvm/pblk-gc.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/drivers/lightnvm/pblk-gc.c b/drivers/lightnvm/pblk-gc.c
index ea9f392a395e..e23b1923b773 100644
--- a/drivers/lightnvm/pblk-gc.c
+++ b/drivers/lightnvm/pblk-gc.c
@@ -64,19 +64,23 @@ static void pblk_put_line_back(struct pblk *pblk, struct pblk_line *line)
 	struct pblk_line_mgmt *l_mg = &pblk->l_mg;
 	struct list_head *move_list;
 
+	spin_lock(&l_mg->gc_lock);
 	spin_lock(&line->lock);
 	WARN_ON(line->state != PBLK_LINESTATE_GC);
 	line->state = PBLK_LINESTATE_CLOSED;
 	trace_pblk_line_state(pblk_disk_name(pblk), line->id,
 					line->state);
+
+	/* We need to reset gc_group in order to ensure that
+	 * pblk_line_gc_list will return proper move_list
+	 * since right now current line is not on any of the
+	 * gc lists.
+	 */
+	line->gc_group = PBLK_LINEGC_NONE;
 	move_list = pblk_line_gc_list(pblk, line);
 	spin_unlock(&line->lock);
-
-	if (move_list) {
-		spin_lock(&l_mg->gc_lock);
-		list_add_tail(&line->list, move_list);
-		spin_unlock(&l_mg->gc_lock);
-	}
+	list_add_tail(&line->list, move_list);
+	spin_unlock(&l_mg->gc_lock);
 }
 
 static void pblk_gc_line_ws(struct work_struct *work)
-- 
2.19.1