[Devel] [PATCH rh7 2/5] cbt: introduce CBT_PAGE_MISSED

[Dmitry Monakhov]

Maxim Patlasov <mpatlasov at virtuozzo.com> writes:

> The patch introduces CBT_PAGE_MISSED -- a special value of cbt->map[i].
> No logic changed. The value will be used by the next patch.
>
> Signed-off-by: Maxim Patlasov <mpatlasov at virtuozzo.com>
ACK
> ---
>  block/blk-cbt.c |   16 ++++++++++------
>  1 file changed, 10 insertions(+), 6 deletions(-)
>
> diff --git a/block/blk-cbt.c b/block/blk-cbt.c
> index 08cefd8..ee225a4 100644
> --- a/block/blk-cbt.c
> +++ b/block/blk-cbt.c
> @@ -16,6 +16,10 @@
>  #define NR_PAGES(bits) (((bits) + PAGE_SIZE*8 - 1) / (PAGE_SIZE*8))
>  #define BITS_PER_PAGE		(1UL << (PAGE_SHIFT + 3))
>  
> +#define CBT_PAGE_MISSED (struct page *)(0x1)
> +#define CBT_PAGE(cbt, idx) (cbt->map[idx] == CBT_PAGE_MISSED ? \
> +			    NULL : cbt->map[idx])
> +
>  static __cacheline_aligned_in_smp DEFINE_MUTEX(cbt_mutex);
>  
>  struct cbt_extent{
> @@ -152,7 +156,7 @@ static int __blk_cbt_set(struct cbt_info  *cbt, blkcnt_t block,
>  					  count);
>  		int ret;
>  
> -		page = cbt->map[idx];
> +		page = CBT_PAGE(cbt, idx);
>  		if (page) {
>  			spin_lock_page(page);
>  			set_bits(page_address(page), off, len, set);
> @@ -300,8 +304,8 @@ void blk_cbt_update_size(struct block_device *bdev)
>  	set_bit(CBT_DEAD, &cbt->flags);
>  	for (idx = 0; idx < to_cpy; idx++){
>  		new->map[idx] = cbt->map[idx];
> -		if (new->map[idx])
> -			get_page(new->map[idx]);
> +		if (CBT_PAGE(new, idx))
> +			get_page(CBT_PAGE(new, idx));
>  	}
>  	rcu_assign_pointer(q->cbt, new);
>  	in_use = cbt->count;
> @@ -351,8 +355,8 @@ static void cbt_release_callback(struct rcu_head *head)
>  	cbt = container_of(head, struct cbt_info, rcu);
>  	nr_pages = NR_PAGES(cbt->block_max);
>  	for (i = 0; i < nr_pages; i++)
> -		if (cbt->map[i])
> -			__free_page(cbt->map[i]);
> +		if (CBT_PAGE(cbt, i))
> +			__free_page(CBT_PAGE(cbt, i));
>  
>  	vfree(cbt->map);
>  	free_percpu(cbt->cache);
> @@ -420,7 +424,7 @@ static void cbt_find_next_extent(struct cbt_info *cbt, blkcnt_t block, struct cb
>  	idx = block >> (PAGE_SHIFT + 3);
>  	while (block < cbt->block_max) {
>  		off = block & (BITS_PER_PAGE -1);
> -		page = cbt->map[idx];
> +		page = CBT_PAGE(cbt, idx);
>  		if (!page) {
>  			if (found)
>  				break;
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