On Wed 21-12-16 23:30:33, Wei Yang wrote:
> memblock_reserve() would add a new range to memblock.reserved in case the
> new range is not totally covered by any of the current memblock.reserved
> range. If the memblock.reserved is full and can't resize,
> memblock_reserve() would fail.
>
> This doesn't happen in real world now, I observed this during code review.
> While theoretically, it has the chance to happen. And if it happens, others
> would think this range of memory is still available and may corrupt the
> memory.
OK, this explains it much better than the previous version! The silent
memory corruption is indeed too hard to debug to have this open even
when the issue is theoretical.
> This patch checks the return value and goto "done" after it succeeds.
>
> Signed-off-by: Wei Yang <richard.weiyang@xxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Thanks!
> ---
> mm/memblock.c | 6 ++----
> 1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/mm/memblock.c b/mm/memblock.c
> index 4929e06..d0f2c96 100644
> --- a/mm/memblock.c
> +++ b/mm/memblock.c
> @@ -1274,18 +1274,17 @@ static void * __init memblock_virt_alloc_internal(
>
> if (max_addr > memblock.current_limit)
> max_addr = memblock.current_limit;
> -
> again:
> alloc = memblock_find_in_range_node(size, align, min_addr, max_addr,
> nid, flags);
> - if (alloc)
> + if (alloc && !memblock_reserve(alloc, size))
> goto done;
>
> if (nid != NUMA_NO_NODE) {
> alloc = memblock_find_in_range_node(size, align, min_addr,
> max_addr, NUMA_NO_NODE,
> flags);
> - if (alloc)
> + if (alloc && !memblock_reserve(alloc, size))
> goto done;
> }
>
> @@ -1303,7 +1302,6 @@ static void * __init memblock_virt_alloc_internal(
>
> return NULL;
> done:
> - memblock_reserve(alloc, size);
> ptr = phys_to_virt(alloc);
> memset(ptr, 0, size);
>
> --
> 2.5.0
--
Michal Hocko
SUSE Labs
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