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dkim=pass header.d=gmail.com header.s=20210112 header.b="L8Id5g/5"; spf=pass (imf08.hostedemail.com: domain of shy828301@gmail.com designates 209.85.216.42 as permitted sender) smtp.mailfrom=shy828301@gmail.com; dmarc=pass (policy=none) header.from=gmail.com X-Rspamd-Server: rspam03 X-HE-Tag: 1662490001-300683 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, Sep 2, 2022 at 7:12 PM Zach O'Keefe wrote: > > 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/ > 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 > --- > mm/khugepaged.c | 7 +------ > 1 file changed, 1 insertion(+), 6 deletions(-) > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index af3b07eb2389..29142a35d24c 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -93,13 +93,8 @@ struct collapse_control { > bool is_khugepaged; > > /* 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 I recall we need this to circumvent some build time warning about stack usage? Or I misremember? > + > /* Last target selected in hpage_collapse_find_target_node() */ > int last_target_node; > }; > -- > 2.37.2.789.g6183377224-goog >