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>
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@ -661,41 +661,70 @@ void bd_forget(struct inode *inode)
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iput(bdev->bd_inode);
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iput(bdev->bd_inode);
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}
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}
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/**
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* bd_may_claim - test whether a block device can be claimed
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* @bdev: block device of interest
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* @whole: whole block device containing @bdev, may equal @bdev
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* @holder: holder trying to claim @bdev
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*
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* Test whther @bdev can be claimed by @holder.
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*
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* CONTEXT:
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* spin_lock(&bdev_lock).
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*
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* RETURNS:
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* %true if @bdev can be claimed, %false otherwise.
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*/
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static bool bd_may_claim(struct block_device *bdev, struct block_device *whole,
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void *holder)
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{
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if (bdev->bd_holder == holder)
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return true; /* already a holder */
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else if (bdev->bd_holder != NULL)
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return false; /* held by someone else */
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else if (bdev->bd_contains == bdev)
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return true; /* is a whole device which isn't held */
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else if (whole->bd_holder == bd_claim)
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return true; /* is a partition of a device that is being partitioned */
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else if (whole->bd_holder != NULL)
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return false; /* is a partition of a held device */
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else
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return true; /* is a partition of an un-held device */
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}
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/**
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* bd_claim - claim a block device
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* @bdev: block device to claim
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* @holder: holder trying to claim @bdev
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*
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* Try to claim @bdev.
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*
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* RETURNS:
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* 0 if successful, -EBUSY if @bdev is already claimed.
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*/
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int bd_claim(struct block_device *bdev, void *holder)
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int bd_claim(struct block_device *bdev, void *holder)
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{
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{
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int res;
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struct block_device *whole = bdev->bd_contains;
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int res = -EBUSY;
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spin_lock(&bdev_lock);
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spin_lock(&bdev_lock);
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/* first decide result */
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if (bd_may_claim(bdev, whole, holder)) {
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if (bdev->bd_holder == holder)
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res = 0; /* already a holder */
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else if (bdev->bd_holder != NULL)
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res = -EBUSY; /* held by someone else */
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else if (bdev->bd_contains == bdev)
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res = 0; /* is a whole device which isn't held */
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else if (bdev->bd_contains->bd_holder == bd_claim)
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res = 0; /* is a partition of a device that is being partitioned */
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else if (bdev->bd_contains->bd_holder != NULL)
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res = -EBUSY; /* is a partition of a held device */
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else
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res = 0; /* is a partition of an un-held device */
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/* now impose change */
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if (res==0) {
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/* note that for a whole device bd_holders
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/* note that for a whole device bd_holders
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* will be incremented twice, and bd_holder will
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* will be incremented twice, and bd_holder will
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* be set to bd_claim before being set to holder
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* be set to bd_claim before being set to holder
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*/
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*/
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bdev->bd_contains->bd_holders ++;
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whole->bd_holders++;
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bdev->bd_contains->bd_holder = bd_claim;
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whole->bd_holder = bd_claim;
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bdev->bd_holders++;
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bdev->bd_holders++;
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bdev->bd_holder = holder;
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bdev->bd_holder = holder;
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res = 0;
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}
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}
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spin_unlock(&bdev_lock);
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spin_unlock(&bdev_lock);
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return res;
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return res;
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}
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}
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EXPORT_SYMBOL(bd_claim);
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EXPORT_SYMBOL(bd_claim);
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void bd_release(struct block_device *bdev)
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void bd_release(struct block_device *bdev)
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