> -----Original Message----- > From: Mike Kravetz [mailto:mike.kravetz@xxxxxxxxxx] > Sent: Friday, July 31, 2020 4:31 AM > To: linux-mm@xxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx > Cc: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>; Michal Nazarewicz > <mina86@xxxxxxxxxx>; Kyungmin Park <kyungmin.park@xxxxxxxxxxx>; > Song Bao Hua (Barry Song) <song.bao.hua@xxxxxxxxxxxxx>; Roman Gushchin > <guro@xxxxxx>; Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>; Mike Kravetz > <mike.kravetz@xxxxxxxxxx>; stable@xxxxxxxxxxxxxxx > Subject: [PATCH] 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 > > Fixes: c64be2bb1c6e ("drivers: add Contiguous Memory Allocator") > Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx> > Cc: <stable@xxxxxxxxxxxxxxx> Acked-by: Barry Song <song.bao.hua@xxxxxxxxxxxxx> > --- > mm/cma.c | 23 +++++++++-------------- > 1 file changed, 9 insertions(+), 14 deletions(-) > > diff --git a/mm/cma.c b/mm/cma.c > index 26ecff818881..0963c0f9c502 100644 > --- a/mm/cma.c > +++ b/mm/cma.c > @@ -93,17 +93,15 @@ static void cma_clear_bitmap(struct cma *cma, > unsigned long pfn, > 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(struct cma > *cma) > 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; > } > -- > 2.25.4
