[Devel] [PATCH rh7] cbt: fix cbt->block_max calculation

[Maxim Patlasov]

When the size of block device is multiple of CBT blocksize, the following:

> cbt->block_max  = (size + blocksize) >> cbt->block_bits;

is incorrect. This may end up in allocating one extra page in cbt->map and
also make various checks with cbt->block_max prone to error.

Signed-off-by: Maxim Patlasov 
---
 block/blk-cbt.c   |2 +-
 drivers/block/ploop/push_backup.c |2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/block/blk-cbt.c b/block/blk-cbt.c
index 8c52bd8..8cdf1d6 100644
--- a/block/blk-cbt.c
+++ b/block/blk-cbt.c
@@ -252,7 +252,7 @@ static struct cbt_info* do_cbt_alloc(struct request_queue 
*q, __u8 *uuid,
return ERR_PTR(-ENOMEM);
 
cbt->block_bits = ilog2(blocksize);
-   cbt->block_max  = (size + blocksize) >> cbt->block_bits;
+   cbt->block_max  = (size + blocksize - 1) >> cbt->block_bits;
spin_lock_init(&cbt->lock);
memcpy(cbt->uuid, uuid, sizeof(cbt->uuid));
cbt->cache = alloc_percpu(struct cbt_extent);
diff --git a/drivers/block/ploop/push_backup.c 
b/drivers/block/ploop/push_backup.c
index 05af67c..4d671a5 100644
--- a/drivers/block/ploop/push_backup.c
+++ b/drivers/block/ploop/push_backup.c
@@ -175,7 +175,7 @@ bool ploop_pb_check_bit(struct ploop_pushbackup_desc *pbd, 
cluster_t clu)
 static int convert_map_to_map(struct ploop_pushbackup_desc *pbd)
 {
struct page **from_map = pbd->cbt_map;
-   blkcnt_t from_max = pbd->cbt_block_max - 1;
+   blkcnt_t from_max = pbd->cbt_block_max;
blkcnt_t from_bits = pbd->cbt_block_bits;
 
struct page **to_map = pbd->ppb_map;

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Re: [Devel] [PATCH rh7] cbt: fix cbt->block_max calculation

[Dmitry Monakhov]

Maxim Patlasov  writes:

> When the size of block device is multiple of CBT blocksize, the following:
>
>> cbt->block_max  = (size + blocksize) >> cbt->block_bits;
Pure typo fix. ACK.
>
> is incorrect. This may end up in allocating one extra page in cbt->map and
> also make various checks with cbt->block_max prone to error.
>
> Signed-off-by: Maxim Patlasov 
> ---
>  block/blk-cbt.c   |2 +-
>  drivers/block/ploop/push_backup.c |2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/block/blk-cbt.c b/block/blk-cbt.c
> index 8c52bd8..8cdf1d6 100644
> --- a/block/blk-cbt.c
> +++ b/block/blk-cbt.c
> @@ -252,7 +252,7 @@ static struct cbt_info* do_cbt_alloc(struct request_queue 
> *q, __u8 *uuid,
>   return ERR_PTR(-ENOMEM);
>  
>   cbt->block_bits = ilog2(blocksize);
> - cbt->block_max  = (size + blocksize) >> cbt->block_bits;
> + cbt->block_max  = (size + blocksize - 1) >> cbt->block_bits;
>   spin_lock_init(&cbt->lock);
>   memcpy(cbt->uuid, uuid, sizeof(cbt->uuid));
>   cbt->cache = alloc_percpu(struct cbt_extent);
> diff --git a/drivers/block/ploop/push_backup.c 
> b/drivers/block/ploop/push_backup.c
> index 05af67c..4d671a5 100644
> --- a/drivers/block/ploop/push_backup.c
> +++ b/drivers/block/ploop/push_backup.c
> @@ -175,7 +175,7 @@ bool ploop_pb_check_bit(struct ploop_pushbackup_desc 
> *pbd, cluster_t clu)
>  static int convert_map_to_map(struct ploop_pushbackup_desc *pbd)
>  {
>   struct page **from_map = pbd->cbt_map;
> - blkcnt_t from_max = pbd->cbt_block_max - 1;
> + blkcnt_t from_max = pbd->cbt_block_max;
>   blkcnt_t from_bits = pbd->cbt_block_bits;
>  
>   struct page **to_map = pbd->ppb_map;


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