linux-kernel - [PATCH 3.16 92/99] block/swim3: Fix -EBUSY error when re-opening device after unmount

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Message-ID: <lsq.1554212308.904763800@decadent.org.uk>
Date:   Tue, 02 Apr 2019 14:38:28 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        linuxppc-dev@...ts.ozlabs.org,
        "Finn Thain" <fthain@...egraphics.com.au>,
        "Jens Axboe" <axboe@...nel.dk>
Subject: [PATCH 3.16 92/99] block/swim3: Fix -EBUSY error when re-opening
 device after unmount

3.16.65-rc1 review patch.  If anyone has any objections, please let me know.

------------------

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

commit 296dcc40f2f2e402facf7cd26cf3f2c8f4b17d47 upstream.

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: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/block/swim3.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

--- a/drivers/block/swim3.c
+++ b/drivers/block/swim3.c
@@ -1027,7 +1027,11 @@ static void floppy_release(struct gendis
 	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);