[Devel] [PATCH rh7 5/5] cbt: add blk_cbt_map_copy_once() helper

[Dmitry Monakhov]

Maxim Patlasov <mpatlasov at virtuozzo.com> writes:

> Ploop will use the helper to make private "snapshot" copy of CBT mask.
>
> Signed-off-by: Maxim Patlasov <mpatlasov at virtuozzo.com>
ACK
> ---
>  block/blk-cbt.c        |   59 ++++++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/blkdev.h |    2 ++
>  2 files changed, 61 insertions(+)
>
> diff --git a/block/blk-cbt.c b/block/blk-cbt.c
> index 4bf9666..850fd7e 100644
> --- a/block/blk-cbt.c
> +++ b/block/blk-cbt.c
> @@ -278,6 +278,65 @@ err_cbt:
>  	return ERR_PTR(-ENOMEM);
>  }
>  
> +int blk_cbt_map_copy_once(struct request_queue *q, struct page ***map_ptr,
> +			  blkcnt_t *block_max, blkcnt_t *block_bits)
> +{
> +	struct cbt_info *cbt;
> +	struct page **map;
> +	unsigned long npages;
> +	unsigned long i;
> +
> +	mutex_lock(&cbt_mutex);
> +	cbt = q->cbt;
> +
> +	BUG_ON(!cbt);
> +	BUG_ON(!cbt->map);
> +	BUG_ON(!cbt->block_max);
> +
> +	cbt_flush_cache(cbt);
> +
> +	npages = NR_PAGES(cbt->block_max);
> +	map = vmalloc(npages * sizeof(void*));
> +	if (!map)
> +		goto fail;
> +
> +	memset(map, 0, npages * sizeof(void*));
> +
> +	for (i = 0; i < npages; i++) {
> +		struct page *page = cbt->map[i];
> +
> +		BUG_ON(page == CBT_PAGE_MISSED);
> +
> +		if (page) {
> +			map[i] = alloc_page(GFP_KERNEL|__GFP_ZERO);
> +			if (!map[i])
> +				goto fail_pages;
> +
> +			spin_lock_page(page);
> +			memcpy(page_address(map[i]), page_address(page),
> +			       PAGE_SIZE);
> +			memset(page_address(page), 0, PAGE_SIZE);
> +			unlock_page(page);
> +		}
> +	}
> +	mutex_unlock(&cbt_mutex);
> +
> +	*map_ptr = map;
> +	*block_max = cbt->block_max;
> +	*block_bits = cbt->block_bits;
> +	return 0;
> +
> +fail_pages:
> +	while (--i >= 0) {
> +		if (map[i])
> +			__free_page(map[i]);
> +	}
> +fail:
> +	vfree(map);
> +	mutex_unlock(&cbt_mutex);
> +	return -ENOMEM;
> +}
> +EXPORT_SYMBOL(blk_cbt_map_copy_once);
>  
>  void blk_cbt_update_size(struct block_device *bdev)
>  {
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index 9dc69cb..7ae962a 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -1651,6 +1651,8 @@ extern void blk_cbt_update_size(struct block_device *bdev);
>  extern void blk_cbt_release(struct request_queue *q);
>  extern void blk_cbt_bio_queue(struct request_queue *q, struct bio *bio);
>  extern int blk_cbt_ioctl(struct block_device *bdev, unsigned cmd, char __user *arg);
> +extern int blk_cbt_map_copy_once(struct request_queue *q, struct page ***map_ptr,
> +				 blkcnt_t *block_max, blkcnt_t *block_bits);
>  #else /* CONFIG_BLK_DEV_CBT */
>  static inline void blk_cbt_update_size(struct block_device *bdev)
>  {
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