linux-kernel - [PATCH 6.0 550/862] md: Remove extra mddev_get() in md_seq

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Message-Id: <20221019083314.271924843@linuxfoundation.org>
Date:   Wed, 19 Oct 2022 10:30:37 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Logan Gunthorpe <logang@...tatee.com>,
        Christoph Hellwig <hch@....de>,
        Guoqing Jiang <Guoqing.jiang@...ux.dev>,
        Song Liu <song@...nel.org>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH 6.0 550/862] md: Remove extra mddev_get() in md_seq_start()

From: Logan Gunthorpe <logang@...tatee.com>

[ Upstream commit 3bfc3bcd787c48aa31e4fde4a6dfcef4cd7ee2c2 ]

A regression is seen where mddev devices stay permanently after they
are stopped due to an elevated reference count.

This was tracked down to an extra mddev_get() in md_seq_start().

It only happened rarely because most of the time the md_seq_start()
is called with a zero offset. The path with an extra mddev_get() only
happens when it starts with a non-zero offset.

The commit noted below changed an mddev_get() to check its success
but inadvertently left the original call in. Remove the extra call.

Fixes: 12a6caf27324 ("md: only delete entries from all_mddevs when the disk is freed")
Signed-off-by: Logan Gunthorpe <logang@...tatee.com>
Reviewed-by: Christoph Hellwig <hch@....de>
Acked-by: Guoqing Jiang <Guoqing.jiang@...ux.dev>
Signed-off-by: Song Liu <song@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/md/md.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 729be2c5296c..470a975e4be9 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -8156,7 +8156,6 @@ static void *md_seq_start(struct seq_file *seq, loff_t *pos)
 	list_for_each(tmp,&all_mddevs)
 		if (!l--) {
 			mddev = list_entry(tmp, struct mddev, all_mddevs);
-			mddev_get(mddev);
 			if (!mddev_get(mddev))
 				continue;
 			spin_unlock(&all_mddevs_lock);
-- 
2.35.1