On Fri, 29 Sep 2023 12:44:15 +0100 Ryan Roberts <ryan.robe...@arm.com> wrote:
> In preparation for adding support for anonymous large folios that are > smaller than the PMD-size, introduce 2 new sysfs files that will be used > to control the new behaviours via the transparent_hugepage interface. > For now, the kernel still only supports PMD-order anonymous THP, so when > reading back anon_orders, it will reflect that. Therefore there are no > behavioural changes intended here. powerpc strikes again. ARCH=powerpc allmodconfig: In file included from ./include/linux/bits.h:6, from ./include/linux/ratelimit_types.h:5, from ./include/linux/printk.h:9, from ./include/asm-generic/bug.h:22, from ./arch/powerpc/include/asm/bug.h:116, from ./include/linux/bug.h:5, from ./include/linux/mmdebug.h:5, from ./include/linux/mm.h:6, from mm/huge_memory.c:8: ./include/vdso/bits.h:7:33: error: initializer element is not constant 7 | #define BIT(nr) (UL(1) << (nr)) | ^ mm/huge_memory.c:77:47: note: in expansion of macro 'BIT' 77 | unsigned int huge_anon_orders __read_mostly = BIT(PMD_ORDER); | ^~~ We keep tripping over this. I wish there was a way to fix it. Style whine: an all-caps identifier is supposed to be a constant, dammit. #define PTE_INDEX_SIZE __pte_index_size Nope. I did this: --- a/mm/huge_memory.c~mm-thp-introduce-anon_orders-and-anon_always_mask-sysfs-files-fix +++ a/mm/huge_memory.c @@ -74,7 +74,7 @@ static unsigned long deferred_split_scan static atomic_t huge_zero_refcount; struct page *huge_zero_page __read_mostly; unsigned long huge_zero_pfn __read_mostly = ~0UL; -unsigned int huge_anon_orders __read_mostly = BIT(PMD_ORDER); +unsigned int huge_anon_orders __read_mostly; static unsigned int huge_anon_always_mask __read_mostly; /** @@ -528,6 +528,9 @@ static int __init hugepage_init_sysfs(st { int err; + /* powerpc's PMD_ORDER isn't a compile-time constant */ + huge_anon_orders = BIT(PMD_ORDER); + *hugepage_kobj = kobject_create_and_add("transparent_hugepage", mm_kobj); if (unlikely(!*hugepage_kobj)) { pr_err("failed to create transparent hugepage kobject\n"); _ I assume this is set up early enough. I don't know why powerpc's PTE_INDEX_SIZE is variable. Hopefully it has been set up by this time and it won't get altered.