block: factor out bd_may_claim()
Factor out bd_may_claim() from bd_claim(), add comments and apply a
couple of cosmetic edits. This is to prepare for further updates to
claim path.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/fs/block_dev.c b/fs/block_dev.c
index 2a6d019..e59440c 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -661,41 +661,70 @@
iput(bdev->bd_inode);
}
+/**
+ * bd_may_claim - test whether a block device can be claimed
+ * @bdev: block device of interest
+ * @whole: whole block device containing @bdev, may equal @bdev
+ * @holder: holder trying to claim @bdev
+ *
+ * Test whther @bdev can be claimed by @holder.
+ *
+ * CONTEXT:
+ * spin_lock(&bdev_lock).
+ *
+ * RETURNS:
+ * %true if @bdev can be claimed, %false otherwise.
+ */
+static bool bd_may_claim(struct block_device *bdev, struct block_device *whole,
+ void *holder)
+{
+ if (bdev->bd_holder == holder)
+ return true; /* already a holder */
+ else if (bdev->bd_holder != NULL)
+ return false; /* held by someone else */
+ else if (bdev->bd_contains == bdev)
+ return true; /* is a whole device which isn't held */
+
+ else if (whole->bd_holder == bd_claim)
+ return true; /* is a partition of a device that is being partitioned */
+ else if (whole->bd_holder != NULL)
+ return false; /* is a partition of a held device */
+ else
+ return true; /* is a partition of an un-held device */
+}
+
+/**
+ * bd_claim - claim a block device
+ * @bdev: block device to claim
+ * @holder: holder trying to claim @bdev
+ *
+ * Try to claim @bdev.
+ *
+ * RETURNS:
+ * 0 if successful, -EBUSY if @bdev is already claimed.
+ */
int bd_claim(struct block_device *bdev, void *holder)
{
- int res;
+ struct block_device *whole = bdev->bd_contains;
+ int res = -EBUSY;
+
spin_lock(&bdev_lock);
- /* first decide result */
- if (bdev->bd_holder == holder)
- res = 0; /* already a holder */
- else if (bdev->bd_holder != NULL)
- res = -EBUSY; /* held by someone else */
- else if (bdev->bd_contains == bdev)
- res = 0; /* is a whole device which isn't held */
-
- else if (bdev->bd_contains->bd_holder == bd_claim)
- res = 0; /* is a partition of a device that is being partitioned */
- else if (bdev->bd_contains->bd_holder != NULL)
- res = -EBUSY; /* is a partition of a held device */
- else
- res = 0; /* is a partition of an un-held device */
-
- /* now impose change */
- if (res==0) {
+ if (bd_may_claim(bdev, whole, holder)) {
/* note that for a whole device bd_holders
* will be incremented twice, and bd_holder will
* be set to bd_claim before being set to holder
*/
- bdev->bd_contains->bd_holders ++;
- bdev->bd_contains->bd_holder = bd_claim;
+ whole->bd_holders++;
+ whole->bd_holder = bd_claim;
bdev->bd_holders++;
bdev->bd_holder = holder;
+ res = 0;
}
+
spin_unlock(&bdev_lock);
return res;
}
-
EXPORT_SYMBOL(bd_claim);
void bd_release(struct block_device *bdev)