| From: "Zach O'Keefe" <zokeefe@google.com> |
| Subject: mm/khugepaged: fix struct collapse_control load_node definition |
| Date: Fri, 2 Sep 2022 19:12:21 -0700 |
| |
| HPAGE_PMD_ORDER is used to determine a minimal amount of bits needed to |
| store per-node counters in struct collapse_control, defining the array to |
| be either a u16[HPAGE_PMD_ORDER] or u32[HPAGE_PMD_ORDER]. |
| |
| For some architectures/configs, HPAGE_PMD_ORDER isn't resolved at |
| preprocessor time (suitable for resolving preprocessor directives) but |
| rather expands into a compiler built-in that is resolved at compile-time. |
| E.g. for 32-bit MIPS (see link for full config): |
| |
| ---8<-- |
| >> arch/mips/include/asm/pgtable.h:238:26: warning: "__builtin_ffs" is not defined, evaluates to 0 [-Wundef] |
| 238 | #define PTE_T_LOG2 (__builtin_ffs(sizeof(pte_t)) - 1) |
| | ^~~~~~~~~~~~~ |
| arch/mips/include/asm/pgtable-32.h:65:43: note: in expansion of macro 'PTE_T_LOG2' |
| 65 | # define PGDIR_SHIFT (2 * PAGE_SHIFT - PTE_T_LOG2 - 1) |
| | ^~~~~~~~~~ |
| include/asm-generic/pgtable-nop4d.h:11:33: note: in expansion of macro 'PGDIR_SHIFT' |
| 11 | #define P4D_SHIFT PGDIR_SHIFT |
| | ^~~~~~~~~~~ |
| include/asm-generic/pgtable-nopud.h:18:25: note: in expansion of macro 'P4D_SHIFT' |
| 18 | #define PUD_SHIFT P4D_SHIFT |
| | ^~~~~~~~~ |
| include/asm-generic/pgtable-nopmd.h:20:25: note: in expansion of macro 'PUD_SHIFT' |
| 20 | #define PMD_SHIFT PUD_SHIFT |
| | ^~~~~~~~~ |
| include/linux/huge_mm.h:109:25: note: in expansion of macro 'PMD_SHIFT' |
| 109 | #define HPAGE_PMD_SHIFT PMD_SHIFT |
| | ^~~~~~~~~ |
| include/linux/huge_mm.h:105:26: note: in expansion of macro 'HPAGE_PMD_SHIFT' |
| 105 | #define HPAGE_PMD_ORDER (HPAGE_PMD_SHIFT-PAGE_SHIFT) |
| | ^~~~~~~~~~~~~~~ |
| mm/khugepaged.c:90:5: note: in expansion of macro 'HPAGE_PMD_ORDER' |
| 90 | #if HPAGE_PMD_ORDER < 16 |
| | ^~~~~~~~~~~~~~~ |
| >> arch/mips/include/asm/pgtable.h:238:39: error: missing binary operator before token "(" |
| 238 | #define PTE_T_LOG2 (__builtin_ffs(sizeof(pte_t)) - 1) |
| | ^ |
| arch/mips/include/asm/pgtable-32.h:65:43: note: in expansion of macro 'PTE_T_LOG2' |
| 65 | # define PGDIR_SHIFT (2 * PAGE_SHIFT - PTE_T_LOG2 - 1) |
| | ^~~~~~~~~~ |
| include/asm-generic/pgtable-nop4d.h:11:33: note: in expansion of macro 'PGDIR_SHIFT' |
| 11 | #define P4D_SHIFT PGDIR_SHIFT |
| | ^~~~~~~~~~~ |
| include/asm-generic/pgtable-nopud.h:18:25: note: in expansion of macro 'P4D_SHIFT' |
| 18 | #define PUD_SHIFT P4D_SHIFT |
| | ^~~~~~~~~ |
| include/asm-generic/pgtable-nopmd.h:20:25: note: in expansion of macro 'PUD_SHIFT' |
| 20 | #define PMD_SHIFT PUD_SHIFT |
| | ^~~~~~~~~ |
| include/linux/huge_mm.h:109:25: note: in expansion of macro 'PMD_SHIFT' |
| 109 | #define HPAGE_PMD_SHIFT PMD_SHIFT |
| | ^~~~~~~~~ |
| include/linux/huge_mm.h:105:26: note: in expansion of macro 'HPAGE_PMD_SHIFT' |
| 105 | #define HPAGE_PMD_ORDER (HPAGE_PMD_SHIFT-PAGE_SHIFT) |
| | ^~~~~~~~~~~~~~~ |
| mm/khugepaged.c:90:5: note: in expansion of macro 'HPAGE_PMD_ORDER' |
| 90 | #if HPAGE_PMD_ORDER < 16 |
| | ^~~~~~~~~~~~~~~ |
| ---8<-- |
| |
| load_node is already special-cased for CONFIG_PPC64 in |
| "mm-khugepaged-add-struct-collapse_control-fix-fix", and we could continue |
| down that path by #define'ing away edge cases, but I think at this point |
| it easier to just let load_node be an array of u32s. If it's ever an |
| issue, we can revisit. |
| |
| This essentially rolls back both: |
| |
| "mm/khugepaged: use minimal bits to store num page < HPAGE_PMD_NR" |
| "mm-khugepaged-add-struct-collapse_control-fix-fix" |
| |
| (though we'll leave it as a u32 vs an int). |
| |
| Link: https://lore.kernel.org/linux-mm/202209021349.F73i5d6X-lkp@intel.com/ |
| Link: https://lkml.kernel.org/r/20220903021221.1130021-1-zokeefe@google.com |
| Fixes: 5f7bb00bd9cd ("mm/khugepaged: use minimal bits to store num page < HPAGE_PMD_NR") |
| Fixes: 03053c821af2 ("mm-khugepaged-add-struct-collapse_control-fix-fix") |
| Signed-off-by: Zach O'Keefe <zokeefe@google.com> |
| Reviewed-by: Yang Shi <shy828301@gmail.com> |
| Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
| --- |
| |
| mm/khugepaged.c | 7 +------ |
| 1 file changed, 1 insertion(+), 6 deletions(-) |
| |
| --- a/mm/khugepaged.c~mm-khugepaged-add-struct-collapse_control-fix-fix-fix |
| +++ a/mm/khugepaged.c |
| @@ -87,13 +87,8 @@ static struct kmem_cache *mm_slot_cache |
| |
| struct collapse_control { |
| /* Num pages scanned per node */ |
| -#if defined(CONFIG_PPC64) |
| u32 node_load[MAX_NUMNODES]; |
| -#elif HPAGE_PMD_ORDER < 16 |
| - u16 node_load[MAX_NUMNODES]; |
| -#else |
| - u32 node_load[MAX_NUMNODES]; |
| -#endif |
| + |
| /* Last target selected in khugepaged_find_target_node() */ |
| int last_target_node; |
| }; |
| _ |
