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: Nick Piggin <npiggin@suse.de> Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
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@ -706,8 +706,13 @@ retry:
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* @bdev is about to be opened exclusively. Check @bdev can be opened
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* exclusively and mark that an exclusive open is in progress. Each
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* successful call to this function must be matched with a call to
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* either bd_claim() or bd_abort_claiming(). If this function
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* succeeds, the matching bd_claim() is guaranteed to succeed.
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* either bd_finish_claiming() or bd_abort_claiming() (which do not
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* fail).
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*
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* This function is used to gain exclusive access to the block device
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* without actually causing other exclusive open attempts to fail. It
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* should be used when the open sequence itself requires exclusive
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* access but may subsequently fail.
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*
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* CONTEXT:
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* Might sleep.
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@ -783,15 +788,47 @@ static void bd_abort_claiming(struct block_device *whole, void *holder)
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__bd_abort_claiming(whole, holder); /* releases bdev_lock */
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}
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/* increment holders when we have a legitimate claim. requires bdev_lock */
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static void __bd_claim(struct block_device *bdev, struct block_device *whole,
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void *holder)
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{
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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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* be set to bd_claim before being set to holder
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*/
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whole->bd_holders++;
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whole->bd_holder = bd_claim;
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bdev->bd_holders++;
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bdev->bd_holder = holder;
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}
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/**
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* bd_finish_claiming - finish claiming a block device
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* @bdev: block device of interest (passed to bd_start_claiming())
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* @whole: whole block device returned by bd_start_claiming()
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* @holder: holder trying to claim @bdev
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*
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* Finish a claiming block started by bd_start_claiming().
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*
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* CONTEXT:
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* Grabs and releases bdev_lock.
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*/
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static void bd_finish_claiming(struct block_device *bdev,
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struct block_device *whole, void *holder)
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{
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spin_lock(&bdev_lock);
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BUG_ON(whole->bd_claiming != holder);
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BUG_ON(!bd_may_claim(bdev, whole, holder));
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__bd_claim(bdev, whole, holder);
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__bd_abort_claiming(whole, holder); /* not actually an abort */
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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 which must have been opened successfully. This
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* function may be called with or without preceding
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* blk_start_claiming(). In the former case, this function is always
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* successful and terminates the claiming block.
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* Try to claim @bdev which must have been opened successfully.
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*
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* CONTEXT:
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* Might sleep.
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@ -807,23 +844,10 @@ int bd_claim(struct block_device *bdev, void *holder)
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might_sleep();
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spin_lock(&bdev_lock);
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res = bd_prepare_to_claim(bdev, whole, holder);
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if (res == 0) {
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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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* be set to bd_claim before being set to holder
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*/
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whole->bd_holders++;
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whole->bd_holder = bd_claim;
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bdev->bd_holders++;
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bdev->bd_holder = holder;
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}
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if (whole->bd_claiming)
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__bd_abort_claiming(whole, holder); /* releases bdev_lock */
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else
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spin_unlock(&bdev_lock);
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if (res == 0)
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__bd_claim(bdev, whole, holder);
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spin_unlock(&bdev_lock);
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return res;
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}
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@ -1477,7 +1501,7 @@ static int blkdev_open(struct inode * inode, struct file * filp)
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if (whole) {
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if (res == 0)
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BUG_ON(bd_claim(bdev, filp) != 0);
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bd_finish_claiming(bdev, whole, filp);
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else
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bd_abort_claiming(whole, filp);
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}
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@ -1713,7 +1737,7 @@ struct block_device *open_bdev_exclusive(const char *path, fmode_t mode, void *h
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if ((mode & FMODE_WRITE) && bdev_read_only(bdev))
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goto out_blkdev_put;
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BUG_ON(bd_claim(bdev, holder) != 0);
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bd_finish_claiming(bdev, whole, holder);
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return bdev;
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out_blkdev_put:
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