The patch titled Subject: cma: don't quit at first error when activating reserved areas has been added to the -mm tree. Its filename is cma-dont-quit-at-first-error-when-activating-reserved-areas.patch

This patch should soon appear at http://ozlabs.org/~akpm/mmots/broken-out/cma-dont-quit-at-first-error-when-a... and later at http://ozlabs.org/~akpm/mmotm/broken-out/cma-dont-quit-at-first-error-when-a...

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------------------------------------------------------ From: Mike Kravetz mike.kravetz@oracle.com Subject: cma: don't quit at first error when activating reserved areas

The routine cma_init_reserved_areas is designed to activate all reserved cma areas. It quits when it first encounters an error. This can leave some areas in a state where they are reserved but not activated. There is no feedback to code which performed the reservation. Attempting to allocate memory from areas in such a state will result in a BUG.

Modify cma_init_reserved_areas to always attempt to activate all areas. The called routine, cma_activate_area is responsible for leaving the area in a valid state. No one is making active use of returned error codes, so change the routine to void.

How to reproduce: This example uses kernelcore, hugetlb and cma as an easy way to reproduce. However, this is a more general cma issue.

Two node x86 VM 16GB total, 8GB per node Kernel command line parameters, kernelcore=4G hugetlb_cma=8G Related boot time messages, hugetlb_cma: reserve 8192 MiB, up to 4096 MiB per node cma: Reserved 4096 MiB at 0x0000000100000000 hugetlb_cma: reserved 4096 MiB on node 0 cma: Reserved 4096 MiB at 0x0000000300000000 hugetlb_cma: reserved 4096 MiB on node 1 cma: CMA area hugetlb could not be activated

# echo 8 > /sys/kernel/mm/hugepages/hugepages-1048576kB/nr_hugepages

BUG: kernel NULL pointer dereference, address: 0000000000000000 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 0 P4D 0 Oops: 0000 [#1] SMP PTI ... Call Trace: bitmap_find_next_zero_area_off+0x51/0x90 cma_alloc+0x1a5/0x310 alloc_fresh_huge_page+0x78/0x1a0 alloc_pool_huge_page+0x6f/0xf0 set_max_huge_pages+0x10c/0x250 nr_hugepages_store_common+0x92/0x120 ? __kmalloc+0x171/0x270 kernfs_fop_write+0xc1/0x1a0 vfs_write+0xc7/0x1f0 ksys_write+0x5f/0xe0 do_syscall_64+0x4d/0x90 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Link: http://lkml.kernel.org/r/20200730163123.6451-1-mike.kravetz@oracle.com Fixes: c64be2bb1c6e ("drivers: add Contiguous Memory Allocator") Signed-off-by: Mike Kravetz mike.kravetz@oracle.com Reviewed-by: Roman Gushchin guro@fb.com Acked-by: Barry Song song.bao.hua@hisilicon.com Cc: Marek Szyprowski m.szyprowski@samsung.com Cc: Michal Nazarewicz mina86@mina86.com Cc: Kyungmin Park kyungmin.park@samsung.com Cc: Joonsoo Kim iamjoonsoo.kim@lge.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

mm/cma.c | 23 +++++++++-------------- 1 file changed, 9 insertions(+), 14 deletions(-)

--- a/mm/cma.c~cma-dont-quit-at-first-error-when-activating-reserved-areas +++ a/mm/cma.c @@ -93,17 +93,15 @@ static void cma_clear_bitmap(struct cma mutex_unlock(&cma->lock); }

-static int __init cma_activate_area(struct cma *cma) +static void __init cma_activate_area(struct cma *cma) { unsigned long base_pfn = cma->base_pfn, pfn = base_pfn; unsigned i = cma->count >> pageblock_order; struct zone *zone;

cma->bitmap = bitmap_zalloc(cma_bitmap_maxno(cma), GFP_KERNEL); - if (!cma->bitmap) { - cma->count = 0; - return -ENOMEM; - } + if (!cma->bitmap) + goto out_error;

WARN_ON_ONCE(!pfn_valid(pfn)); zone = page_zone(pfn_to_page(pfn)); @@ -133,25 +131,22 @@ static int __init cma_activate_area(stru spin_lock_init(&cma->mem_head_lock); #endif

- return 0; + return;

not_in_zone: - pr_err("CMA area %s could not be activated\n", cma->name); bitmap_free(cma->bitmap); +out_error: cma->count = 0; - return -EINVAL; + pr_err("CMA area %s could not be activated\n", cma->name); + return; }

static int __init cma_init_reserved_areas(void) { int i;

- for (i = 0; i < cma_area_count; i++) { - int ret = cma_activate_area(&cma_areas[i]); - - if (ret) - return ret; - } + for (i = 0; i < cma_area_count; i++) + cma_activate_area(&cma_areas[i]);

return 0; } _

Patches currently in -mm which might be from mike.kravetz@oracle.com are

hugetlbfs-prevent-filesystem-stacking-of-hugetlbfs.patch cma-dont-quit-at-first-error-when-activating-reserved-areas.patch