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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>
This commit is contained in:
Tejun Heo 2010-04-07 18:52:29 +09:00 committed by Jens Axboe
parent afc24d49c1
commit 1a3cbbc5a5
1 changed files with 50 additions and 21 deletions
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71
fs/block_dev.c
View File

@ -661,41 +661,70 @@ void bd_forget(struct inode *inode)
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)