linux-kernel - [PATCH AUTOSEL 4.20 286/304] block/swim3: Fix -EBUSY error when re-opening device after unmount

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Message-Id: <20190128154341.47195-286-sashal@kernel.org>
Date:   Mon, 28 Jan 2019 10:43:23 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Finn Thain <fthain@...egraphics.com.au>,
        linuxppc-dev@...ts.ozlabs.org, Jens Axboe <axboe@...nel.dk>,
        Sasha Levin <sashal@...nel.org>, linux-block@...r.kernel.org
Subject: [PATCH AUTOSEL 4.20 286/304] block/swim3: Fix -EBUSY error when re-opening device after unmount

From: Finn Thain <fthain@...egraphics.com.au>

[ Upstream commit 296dcc40f2f2e402facf7cd26cf3f2c8f4b17d47 ]

When the block device is opened with FMODE_EXCL, ref_count is set to -1.
This value doesn't get reset when the device is closed which means the
device cannot be opened again. Fix this by checking for refcount <= 0
in the release method.

Reported-and-tested-by: Stan Johnson <userm57@...oo.com>
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: linuxppc-dev@...ts.ozlabs.org
Signed-off-by: Finn Thain <fthain@...egraphics.com.au>
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/block/swim3.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/block/swim3.c b/drivers/block/swim3.c
index c1c676a33e4a..3f6df3f1f5d9 100644
--- a/drivers/block/swim3.c
+++ b/drivers/block/swim3.c
@@ -995,7 +995,11 @@ static void floppy_release(struct gendisk *disk, fmode_t mode)
 	struct swim3 __iomem *sw = fs->swim3;
 
 	mutex_lock(&swim3_mutex);
-	if (fs->ref_count > 0 && --fs->ref_count == 0) {
+	if (fs->ref_count > 0)
+		--fs->ref_count;
+	else if (fs->ref_count == -1)
+		fs->ref_count = 0;
+	if (fs->ref_count == 0) {
 		swim3_action(fs, MOTOR_OFF);
 		out_8(&sw->control_bic, 0xff);
 		swim3_select(fs, RELAX);
-- 
2.19.1