Hi Adrien,
> -----Original Message-----
> From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Adrien Mazarguil
> Sent: Monday, May 25, 2015 5:28 PM
> To: dev at dpdk.org
> Subject: [dpdk-dev] [PATCH 2/2] mempool: fix pages computation to determine
> number of objects
>
> In rte_mempool_obj_iter(), even when a single page is required per object,
> a loop checks that the the next page is contiguous and drops the first one
> otherwise. This commit checks subsequent pages only when several are
> required per object.
>
> Also a minor fix for the amount of remaining space that prevents using the
> entire region.
>
> Fixes: 148f963fb532 ("xen: core library changes")
>
> Signed-off-by: Adrien Mazarguil <adrien.mazarguil at 6wind.com>
> ---
> lib/librte_mempool/rte_mempool.c | 11 ++++++++---
> 1 file changed, 8 insertions(+), 3 deletions(-)
>
> diff --git a/lib/librte_mempool/rte_mempool.c
> b/lib/librte_mempool/rte_mempool.c
> index d1a02a2..3c1efec 100644
> --- a/lib/librte_mempool/rte_mempool.c
> +++ b/lib/librte_mempool/rte_mempool.c
> @@ -175,12 +175,17 @@ rte_mempool_obj_iter(void *vaddr, uint32_t elt_num,
> size_t elt_sz, size_t align,
> pgn += j;
>
> /* do we have enough space left for the next element. */
> - if (pgn >= pg_num)
> + if (pgn > pg_num)
> break;
Hmm, that doesn't look right.
Suppose:
start==0; end==5120; pg_shift==12; pg_num == 1;
So:
pgn = 1; // (5120>>12)-(0>>12)
And we end-up accessing element that is beyond allocated memory.
>
> - for (k = j;
> + /*
> + * Compute k so that (k - j) is the number of contiguous
> + * pages starting from index j. Note that there is at least
> + * one page.
> + */
> + for (k = j + 1;
> k != pgn &&
> - paddr[k] + pg_sz == paddr[k + 1];
> + paddr[k - 1] + pg_sz == paddr[k];
> k++)
> ;
Again, suppose:
j==0; start==0; end==2048; pg_shift==12; pg_num == 2;
So:
pgn = 0;
k = 1;
and the loop goes beyond paddr[] boundaries.
The problem here, I think that you treat pgn as number of pages, while it is
index of last page to be used.
As I understand, what you are trying to fix here, is a situation when end is a
multiply of page size (end == N * pg_sz), right?
Then, probably something simple like that would do:
- pgn = (end >> pg_shift) - (start >> pg_shift);
+ pgn = (end - 1 >> pg_shift) - (start >> pg_shift);
+ pg_next = (end >> pg_shift) - (start >> pg_shift);
...
if (k == pgn) {
if (obj_iter != NULL)
obj_iter(obj_iter_arg, (void *)start,
(void *)end, i);
va = end;
- j = pgn;
+ j = pg_next;
i++;
} else {
...
Konstantin
>
> --
> 2.1.0
