On Wed, 18 Jan 2023 17:05:23 +0900 Levi Yun <ppbuk5246@xxxxxxxxx> wrote: > Suppose, memblock_alloc_ranged_nid with highmem_start is success > when cma_declare_contiguous_nid is called with !fixed > in the system 32-bit system with PHYS_ADDR_T_64BIT enabled > with memblock.bottom_up == false. > > But, Next trial to memblock_alloc_range_nid to allocate in > [SIZE_4G, limits) nullifies former success allocated addr and > it retries to memblock_alloc_ragne_nid again. > > In this situation, first success address area is lost. > > By changing order of allocation (SIZE_4G, high_memory and base) and > checking whether allocated prevents potential memory lost. > The changelog is hard to follow. I redid it as below - please review and correct if needed? From: Levi Yun <ppbuk5246@xxxxxxxxx> Subject: mm/cma: fix potential memory loss on cma_declare_contiguous_nid Date: Wed, 18 Jan 2023 17:05:23 +0900 Suppose memblock_alloc_range_nid() with highmem_start succeeds when cma_declare_contiguous_nid is called with !fixed on a 32-bit system with PHYS_ADDR_T_64BIT enabled with memblock.bottom_up == false. But the next trial to memblock_alloc_range_nid() to allocate in [SIZE_4G, limits) nullifies former successfully allocated addr and it retries memblock_alloc_ragne_nid(). In this situation, the first successfully allocated address area is lost. Change the order of allocation (SIZE_4G, high_memory and base) and check whether the allocated succeeded to prevent potential memory loss. Link: https://lkml.kernel.org/r/20230118080523.44522-1-ppbuk5246@xxxxxxxxx Signed-off-by: Levi Yun <ppbuk5246@xxxxxxxxx> Cc: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx> Cc: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx> Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> Cc: Minchan Kim <minchan@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/cma.c | 24 ++++++++++++------------ 1 file changed, 12 insertions(+), 12 deletions(-) --- a/mm/cma.c~mm-cma-fix-potential-memory-loss-on-cma_declare_contiguous_nid +++ a/mm/cma.c @@ -331,18 +331,6 @@ int __init cma_declare_contiguous_nid(ph phys_addr_t addr = 0; /* - * All pages in the reserved area must come from the same zone. - * If the requested region crosses the low/high memory boundary, - * try allocating from high memory first and fall back to low - * memory in case of failure. - */ - if (base < highmem_start && limit > highmem_start) { - addr = memblock_alloc_range_nid(size, alignment, - highmem_start, limit, nid, true); - limit = highmem_start; - } - - /* * If there is enough memory, try a bottom-up allocation first. * It will place the new cma area close to the start of the node * and guarantee that the compaction is moving pages out of the @@ -359,6 +347,18 @@ int __init cma_declare_contiguous_nid(ph } #endif + /* + * All pages in the reserved area must come from the same zone. + * If the requested region crosses the low/high memory boundary, + * try allocating from high memory first and fall back to low + * memory in case of failure. + */ + if (!addr && base < highmem_start && limit > highmem_start) { + addr = memblock_alloc_range_nid(size, alignment, + highmem_start, limit, nid, true); + limit = highmem_start; + } + if (!addr) { addr = memblock_alloc_range_nid(size, alignment, base, limit, nid, true); _
