From b4903d6e8408e6137ee4666ee67ec566b74a0f05 Mon Sep 17 00:00:00 2001 From: Andrey Ryabinin Date: Wed, 30 Jul 2014 16:08:35 -0700 Subject: [PATCH] mm: debugfs: move rounddown_pow_of_two() out from do_fault path do_fault_around() expects fault_around_bytes rounded down to nearest page order. Instead of calling rounddown_pow_of_two every time in fault_around_pages()/fault_around_mask() we could do round down when user changes fault_around_bytes via debugfs interface. This also fixes bug when user set fault_around_bytes to 0. Result of rounddown_pow_of_two(0) is not defined, therefore fault_around_bytes == 0 doesn't work without this patch. Let's set fault_around_bytes to PAGE_SIZE if user sets to something less than PAGE_SIZE [akpm@linux-foundation.org: tweak code layout] Fixes: a9b0f861("mm: nominate faultaround area in bytes rather than page order") Signed-off-by: Andrey Ryabinin Reported-by: Sasha Levin Acked-by: Kirill A. Shutemov Cc: [3.15.x] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/memory.c | 21 ++++++++++++--------- 1 file changed, 12 insertions(+), 9 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index 7e8d8205b610..8b44f765b645 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2758,23 +2758,18 @@ void do_set_pte(struct vm_area_struct *vma, unsigned long address, update_mmu_cache(vma, address, pte); } -static unsigned long fault_around_bytes = 65536; +static unsigned long fault_around_bytes = rounddown_pow_of_two(65536); -/* - * fault_around_pages() and fault_around_mask() round down fault_around_bytes - * to nearest page order. It's what do_fault_around() expects to see. - */ static inline unsigned long fault_around_pages(void) { - return rounddown_pow_of_two(fault_around_bytes) / PAGE_SIZE; + return fault_around_bytes >> PAGE_SHIFT; } static inline unsigned long fault_around_mask(void) { - return ~(rounddown_pow_of_two(fault_around_bytes) - 1) & PAGE_MASK; + return ~(fault_around_bytes - 1) & PAGE_MASK; } - #ifdef CONFIG_DEBUG_FS static int fault_around_bytes_get(void *data, u64 *val) { @@ -2782,11 +2777,19 @@ static int fault_around_bytes_get(void *data, u64 *val) return 0; } +/* + * fault_around_pages() and fault_around_mask() expects fault_around_bytes + * rounded down to nearest page order. It's what do_fault_around() expects to + * see. + */ static int fault_around_bytes_set(void *data, u64 val) { if (val / PAGE_SIZE > PTRS_PER_PTE) return -EINVAL; - fault_around_bytes = val; + if (val > PAGE_SIZE) + fault_around_bytes = rounddown_pow_of_two(val); + else + fault_around_bytes = PAGE_SIZE; /* rounddown_pow_of_two(0) is undefined */ return 0; } DEFINE_SIMPLE_ATTRIBUTE(fault_around_bytes_fops, -- 2.20.1