[PATCH 4/8] ublk: simplify ublk_ch_open and ublk_ch_release

From: Christoph Hellwig <hch@lst.de>
To: Ming Lei <ming.lei@redhat.com>, Jens Axboe <axboe@kernel.dk>
Cc: linux-block@vger.kernel.org
Subject: [PATCH 4/8] ublk: simplify ublk_ch_open and ublk_ch_release
Date: Thu, 21 Jul 2022 07:16:28 +0200	[thread overview]
Message-ID: <20220721051632.1676890-5-hch@lst.de> (raw)
In-Reply-To: <20220721051632.1676890-1-hch@lst.de>

fops->open and fops->release are always paired.  Use simple atomic bit
ops ot indicate if the device is opened instead of a count that can
only be 0 and 1 and a useless cmpxchg loop in ublk_ch_release.

Also don't bother clearing file->private_data is the file is about to
be freed anyway.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/block/ublk_drv.c | 17 +++++++----------
 1 file changed, 7 insertions(+), 10 deletions(-)

diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
index deabcb23ae2af..1f7bbbc3276a2 100644
--- a/drivers/block/ublk_drv.c
+++ b/drivers/block/ublk_drv.c
@@ -125,7 +125,8 @@ struct ublk_device {
 	struct cdev		cdev;
 	struct device		cdev_dev;
 
-	atomic_t		ch_open_cnt;
+#define UB_STATE_OPEN		(1 << 0)
+	unsigned long		state;
 	int			ub_number;
 
 	struct mutex		mutex;
@@ -647,21 +648,17 @@ static int ublk_ch_open(struct inode *inode, struct file *filp)
 	struct ublk_device *ub = container_of(inode->i_cdev,
 			struct ublk_device, cdev);
 
-	if (atomic_cmpxchg(&ub->ch_open_cnt, 0, 1) == 0) {
-		filp->private_data = ub;
-		return 0;
-	}
-	return -EBUSY;
+	if (test_and_set_bit(UB_STATE_OPEN, &ub->state))
+		return -EBUSY;
+	filp->private_data = ub;
+	return 0;
 }
 
 static int ublk_ch_release(struct inode *inode, struct file *filp)
 {
 	struct ublk_device *ub = filp->private_data;
 
-	while (atomic_cmpxchg(&ub->ch_open_cnt, 1, 0) != 1)
-		cpu_relax();
-
-	filp->private_data = NULL;
+	clear_bit(UB_STATE_OPEN, &ub->state);
 	return 0;
 }
 
-- 
2.30.2

