[PATCH] block/swim3: Fix -EBUSY error when re-opening device after unmount

[Finn Thain]

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@xxxxxxxxx>
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: linuxppc-dev@xxxxxxxxxxxxxxxx
Signed-off-by: Finn Thain <fthain@xxxxxxxxxxxxxxxxxxx>
---
 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 ba1190f1276b..87ca8f207c7c 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);
-- 
2.19.2