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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>
This commit is contained in:
Christoph Hellwig 2023-06-01 11:44:45 +02:00 committed by Jens Axboe
parent 0783b1a7cb
commit ae5f855ead
1 changed files with 21 additions and 17 deletions
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38
block/bdev.c
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@ -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 */
struct block_device *whole = bdev_whole(bdev);
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 */
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