block: refactor bd_may_claim

The long if/else chain obsfucates the actual logic.  Tidy it up to be
more structured.  Also drop the whole argument, as it can be trivially
derived from bdev using bdev_whole, and having the bdev_whole in the
function makes it easier to follow.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Link: https://lore.kernel.org/r/20230601094459.1350643-3-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/bdev.c b/block/bdev.c
index 317bfd9..080b5c8 100644 (file)
--- a/block/bdev.c
+++ b/block/bdev.c
@@ -463,7 +463,6 @@ long nr_blockdev_pages(void)
 /**
  * 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 whether @bdev can be claimed by @holder.
@@ -474,22 +473,27 @@ long nr_blockdev_pages(void)
  * RETURNS:
  * %true if @bdev can be claimed, %false otherwise.
  */
-static bool bd_may_claim(struct block_device *bdev, struct block_device *whole,
-                        void *holder)
+static bool bd_may_claim(struct block_device *bdev, 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 (whole == bdev)
-               return true;     /* is a whole device which isn't held */
-
-       else if (whole->bd_holder == bd_may_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 */
+       struct block_device *whole = bdev_whole(bdev);
+
+       if (bdev->bd_holder) {
+               /*
+                * The same holder can always re-claim.
+                */
+               if (bdev->bd_holder == holder)
+                       return true;
+               return false;
+       }
+
+       /*
+        * If the whole devices holder is set to bd_may_claim, a partition on
+        * the device is claimed, but not the whole device.
+        */
+       if (whole != bdev &&
+           whole->bd_holder && whole->bd_holder != bd_may_claim)
+               return false;
+       return true;
 }
 
 /**
@@ -513,7 +517,7 @@ int bd_prepare_to_claim(struct block_device *bdev, void *holder)
 retry:
        spin_lock(&bdev_lock);
        /* if someone else claimed, fail */
-       if (!bd_may_claim(bdev, whole, holder)) {
+       if (!bd_may_claim(bdev, holder)) {
                spin_unlock(&bdev_lock);
                return -EBUSY;
        }
@@ -559,7 +563,7 @@ static void bd_finish_claiming(struct block_device *bdev, void *holder)
        struct block_device *whole = bdev_whole(bdev);
 
        spin_lock(&bdev_lock);
-       BUG_ON(!bd_may_claim(bdev, whole, holder));
+       BUG_ON(!bd_may_claim(bdev, holder));
        /*
         * Note that for a whole device bd_holders will be incremented twice,
         * and bd_holder will be set to bd_may_claim before being set to holder