On Fri, 19 Apr 2024 10:09:10 +0530 Hariom Panthi <hariom1.p@xxxxxxxxxxx> wrote:
> In vmap_pte_range, BUG_ON is called when page is already mapped,
> It doesn't give enough information to debug further.
> Dumping page owner information alongwith BUG_ON will be more useful
> in case of multiple page mapping.
>
> Example:
> [ 18.258806] page_owner tracks the page as allocated
> [ 18.258970] page last allocated via order 0, migratetype Unmovable, gfp_mask 0xcc0(GFP_KERNEL), pid 81, tgid 81 (insmod), ts 18257811008, free_ts 0
> [ 18.259327] prep_new_page+0xa8/0x10c
> [ 18.259455] get_page_from_freelist+0x7f8/0x1248
> [ 18.259591] __alloc_pages+0x164/0x2b4
> [ 18.259703] alloc_pages_mpol+0x88/0x230
> [ 18.259821] alloc_pages+0x4c/0x7c
> [ 18.259923] load_module+0x74/0x1af4
> [ 18.260031] __do_sys_init_module+0x190/0x1fc
> [ 18.260154] __arm64_sys_init_module+0x1c/0x28
> [ 18.260280] invoke_syscall+0x44/0x108
> [ 18.260394] el0_svc_common.constprop.0+0x40/0xe0
> [ 18.260530] do_el0_svc_compat+0x1c/0x34
> [ 18.260647] el0_svc_compat+0x2c/0x80
> [ 18.260761] el0t_32_sync_handler+0x90/0x140
> [ 18.260887] el0t_32_sync+0x194/0x198
> [ 18.260996] page_owner free stack trace missing
> [ 18.261143] ------------[ cut here ]------------
> [ 18.261272] kernel BUG at mm/vmalloc.c:113!
>
> ...
>
> @@ -103,7 +105,13 @@ static int vmap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
> if (!pte)
> return -ENOMEM;
> do {
> - BUG_ON(!pte_none(ptep_get(pte)));
> + if (!pte_none(ptep_get(pte))) {
> + if (pfn_valid(pfn)) {
> + page = pfn_to_page(pfn);
> + dump_page_owner(page);
> + }
> + BUG();
> + }
Diving straight into dump_page_owner() seems inappropriate. The
higher-level dump_page() interface is more typically used.
Or, even more common, VM_BUG_ON_PAGE(), but that doesn't look to be a
good fit here.
