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Commit b0018361 authored by Nick Piggin's avatar Nick Piggin Committed by Jens Axboe
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block: bd_start_claiming cleanup 



I don't like the subtle multi-context code in bd_claim (ie.  detects where it
has been called based on bd_claiming). It seems clearer to just require a new
function to finish a 2-part claim.

Also improve commentary in bd_start_claiming as to how it should
be used.

Signed-off-by: default avatarNick Piggin <npiggin@suse.de>
Acked-by: default avatarTejun Heo <tj@kernel.org>
Signed-off-by: default avatarJens Axboe <jaxboe@fusionio.com>
parent cf342570

fs/block_dev.c

+48 −24
Original line number Diff line number Diff line
@@ -706,8 +706,13 @@ static int bd_prepare_to_claim(struct block_device *bdev, 
 * @bdev is about to be opened exclusively.  Check @bdev can be opened

 * exclusively and mark that an exclusive open is in progress.  Each

 * successful call to this function must be matched with a call to

 * either bd_claim() or bd_abort_claiming().  If this function

 * succeeds, the matching bd_claim() is guaranteed to succeed.

 * either bd_finish_claiming() or bd_abort_claiming() (which do not

 * fail).

 *

 * This function is used to gain exclusive access to the block device

 * without actually causing other exclusive open attempts to fail. It

 * should be used when the open sequence itself requires exclusive

 * access but may subsequently fail.

 *

 * CONTEXT:

 * Might sleep.
@@ -783,15 +788,47 @@ static void bd_abort_claiming(struct block_device *whole, void *holder) 
	__bd_abort_claiming(whole, holder);		/* releases bdev_lock */

}



/* increment holders when we have a legitimate claim. requires bdev_lock */

static void __bd_claim(struct block_device *bdev, struct block_device *whole,

					void *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

	 */

	whole->bd_holders++;

	whole->bd_holder = bd_claim;

	bdev->bd_holders++;

	bdev->bd_holder = holder;

}



/**

 * bd_finish_claiming - finish claiming a block device

 * @bdev: block device of interest (passed to bd_start_claiming())

 * @whole: whole block device returned by bd_start_claiming()

 * @holder: holder trying to claim @bdev

 *

 * Finish a claiming block started by bd_start_claiming().

 *

 * CONTEXT:

 * Grabs and releases bdev_lock.

 */

static void bd_finish_claiming(struct block_device *bdev,

				struct block_device *whole, void *holder)

{

	spin_lock(&bdev_lock);

	BUG_ON(whole->bd_claiming != holder);

	BUG_ON(!bd_may_claim(bdev, whole, holder));

	__bd_claim(bdev, whole, holder);

	__bd_abort_claiming(whole, holder); /* not actually an abort */

}



/**

 * bd_claim - claim a block device

 * @bdev: block device to claim

 * @holder: holder trying to claim @bdev

 *

 * Try to claim @bdev which must have been opened successfully.  This

 * function may be called with or without preceding

 * blk_start_claiming().  In the former case, this function is always

 * successful and terminates the claiming block.

 * Try to claim @bdev which must have been opened successfully.

 *

 * CONTEXT:

 * Might sleep.
@@ -807,22 +844,9 @@ int bd_claim(struct block_device *bdev, void *holder) 
	might_sleep();



	spin_lock(&bdev_lock);



	res = bd_prepare_to_claim(bdev, whole, holder);

	if (res == 0) {

		/* 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

		 */

		whole->bd_holders++;

		whole->bd_holder = bd_claim;

		bdev->bd_holders++;

		bdev->bd_holder = holder;

	}



	if (whole->bd_claiming)

		__bd_abort_claiming(whole, holder);	/* releases bdev_lock */

	else

	if (res == 0)

		__bd_claim(bdev, whole, holder);

	spin_unlock(&bdev_lock);



	return res;
@@ -1477,7 +1501,7 @@ static int blkdev_open(struct inode * inode, struct file * filp) 


	if (whole) {

		if (res == 0)

			BUG_ON(bd_claim(bdev, filp) != 0);

			bd_finish_claiming(bdev, whole, filp);

		else

			bd_abort_claiming(whole, filp);

	}
@@ -1713,7 +1737,7 @@ struct block_device *open_bdev_exclusive(const char *path, fmode_t mode, void *h 
	if ((mode & FMODE_WRITE) && bdev_read_only(bdev))

		goto out_blkdev_put;



	BUG_ON(bd_claim(bdev, holder) != 0);

	bd_finish_claiming(bdev, whole, holder);

	return bdev;



out_blkdev_put: