block: refactor bd_start_claiming

mainline inclusion
from mainline-v5.9-rc1
commit 58e46ed9
category: bugfix
bugzilla: 41569
CVE: NA

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

Move the locking and assignment of bd_claiming from bd_start_claiming to
bd_prepare_to_claim.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Acked-by: NTejun Heo <tj@kernel.org>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

conflcit:
fs/block_dev.c
Signed-off-by: NYe Bin <yebin10@huawei.com>
Reviewed-by: Nzhangyi (F) <yi.zhang@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

fs/block_dev.c

@@ -1033,19 +1033,14 @@ static bool bd_may_claim(struct block_device *bdev, struct block_device *whole,
 }
 
 /**
- * bd_prepare_to_claim - prepare to claim a block device
+ * bd_prepare_to_claim - claim a block device
  * @bdev: block device of interest
  * @whole: the whole device containing @bdev, may equal @bdev
  * @holder: holder trying to claim @bdev
  *
- * Prepare to claim @bdev.  This function fails if @bdev is already
- * claimed by another holder and waits if another claiming is in
- * progress.  This function doesn't actually claim.  On successful
- * return, the caller has ownership of bd_claiming and bd_holder[s].
- *
- * CONTEXT:
- * spin_lock(&bdev_lock).  Might release bdev_lock, sleep and regrab
- * it multiple times.
+ * Claim @bdev.  This function fails if @bdev is already claimed by another
+ * holder and waits if another claiming is in progress. return, the caller
+ * has ownership of bd_claiming and bd_holder[s].
  *
  * RETURNS:
  * 0 if @bdev can be claimed, -EBUSY otherwise.
@@ -1054,9 +1049,12 @@ static int bd_prepare_to_claim(struct block_device *bdev,
 			       struct block_device *whole, void *holder)
 {
 retry:
+	spin_lock(&bdev_lock);
 	/* if someone else claimed, fail */
-	if (!bd_may_claim(bdev, whole, holder))
+	if (!bd_may_claim(bdev, whole, holder)) {
+		spin_unlock(&bdev_lock);
 		return -EBUSY;
+	}
 
 	/* if claiming is already in progress, wait for it to finish */
 	if (whole->bd_claiming) {
@@ -1067,11 +1065,12 @@ static int bd_prepare_to_claim(struct block_device *bdev,
 		spin_unlock(&bdev_lock);
 		schedule();
 		finish_wait(wq, &wait);
-		spin_lock(&bdev_lock);
 		goto retry;
 	}
 
 	/* yay, all mine */
+	whole->bd_claiming = holder;
+	spin_unlock(&bdev_lock);
 	return 0;
 }
 
@@ -1153,19 +1152,13 @@ static struct block_device *bd_start_claiming(struct block_device *bdev,
 	if (!whole)
 		return ERR_PTR(-ENOMEM);
 
-	/* prepare to claim, if successful, mark claiming in progress */
-	spin_lock(&bdev_lock);
-
 	err = bd_prepare_to_claim(bdev, whole, holder);
-	if (err == 0) {
-		whole->bd_claiming = holder;
-		spin_unlock(&bdev_lock);
-		return whole;
-	} else {
-		spin_unlock(&bdev_lock);
+	if (err) {
 		bdput(whole);
 		return ERR_PTR(err);
 	}
+
+	return whole;
 }
 
 #ifdef CONFIG_SYSFS