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Message-ID: <70915836-28d4-ccfb-01cc-e0c2a0251350@c-s.fr>
Date: Fri, 22 Jun 2018 18:17:53 +0200
From: Christophe LEROY <christophe.leroy@....fr>
To: Mathieu Malaterre <malat@...ian.org>
Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Paul Mackerras <paulus@...ba.org>,
Michael Ellerman <mpe@...erman.id.au>,
"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
LKML <linux-kernel@...r.kernel.org>,
linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>
Subject: Re: [PATCH] powerpc/mm: fix always true/false warning in slice.c
Le 22/06/2018 à 16:55, Mathieu Malaterre a écrit :
> On Fri, Jun 22, 2018 at 3:49 PM Christophe Leroy
> <christophe.leroy@....fr> wrote:
>>
>> This patch fixes the following warnings (obtained with make W=1).
>>
>> arch/powerpc/mm/slice.c: In function 'slice_range_to_mask':
>> arch/powerpc/mm/slice.c:73:12: error: comparison is always true due to limited range of data type [-Werror=type-limits]
>> if (start < SLICE_LOW_TOP) {
>> ^
>> arch/powerpc/mm/slice.c:81:20: error: comparison is always false due to limited range of data type [-Werror=type-limits]
>> if ((start + len) > SLICE_LOW_TOP) {
>> ^
>> arch/powerpc/mm/slice.c: In function 'slice_mask_for_free':
>> arch/powerpc/mm/slice.c:136:17: error: comparison is always true due to limited range of data type [-Werror=type-limits]
>> if (high_limit <= SLICE_LOW_TOP)
>> ^
>> arch/powerpc/mm/slice.c: In function 'slice_check_range_fits':
>> arch/powerpc/mm/slice.c:185:12: error: comparison is always true due to limited range of data type [-Werror=type-limits]
>> if (start < SLICE_LOW_TOP) {
>> ^
>> arch/powerpc/mm/slice.c:195:39: error: comparison is always false due to limited range of data type [-Werror=type-limits]
>> if (SLICE_NUM_HIGH && ((start + len) > SLICE_LOW_TOP)) {
>> ^
>> arch/powerpc/mm/slice.c: In function 'slice_scan_available':
>> arch/powerpc/mm/slice.c:306:11: error: comparison is always true due to limited range of data type [-Werror=type-limits]
>> if (addr < SLICE_LOW_TOP) {
>> ^
>> arch/powerpc/mm/slice.c: In function 'get_slice_psize':
>> arch/powerpc/mm/slice.c:709:11: error: comparison is always true due to limited range of data type [-Werror=type-limits]
>> if (addr < SLICE_LOW_TOP) {
>> ^
>>
>> Signed-off-by: Christophe Leroy <christophe.leroy@....fr>
>> ---
>> arch/powerpc/mm/slice.c | 21 ++++++++++++++-------
>> 1 file changed, 14 insertions(+), 7 deletions(-)
>>
>> diff --git a/arch/powerpc/mm/slice.c b/arch/powerpc/mm/slice.c
>> index 9530c6db406a..17c57760e06c 100644
>> --- a/arch/powerpc/mm/slice.c
>> +++ b/arch/powerpc/mm/slice.c
>> @@ -62,6 +62,13 @@ static void slice_print_mask(const char *label, const struct slice_mask *mask) {
>>
>> #endif
>>
>> +static inline bool slice_addr_is_low(unsigned long addr)
>> +{
>> + u64 tmp = (u64)addr;
>> +
>> + return tmp < SLICE_LOW_TOP;
>> +}
>> +
>> static void slice_range_to_mask(unsigned long start, unsigned long len,
>> struct slice_mask *ret)
>> {
>> @@ -71,7 +78,7 @@ static void slice_range_to_mask(unsigned long start, unsigned long len,
>> if (SLICE_NUM_HIGH)
>> bitmap_zero(ret->high_slices, SLICE_NUM_HIGH);
>>
>> - if (start < SLICE_LOW_TOP) {
>> + if (slice_addr_is_low(start)) {
>> unsigned long mend = min(end,
>> (unsigned long)(SLICE_LOW_TOP - 1));
>>
>> @@ -79,7 +86,7 @@ static void slice_range_to_mask(unsigned long start, unsigned long len,
>> - (1u << GET_LOW_SLICE_INDEX(start));
>> }
>>
>> - if ((start + len) > SLICE_LOW_TOP) {
>> + if (!slice_addr_is_low(end)) {
>> unsigned long start_index = GET_HIGH_SLICE_INDEX(start);
>> unsigned long align_end = ALIGN(end, (1UL << SLICE_HIGH_SHIFT));
>> unsigned long count = GET_HIGH_SLICE_INDEX(align_end) - start_index;
>> @@ -134,7 +141,7 @@ static void slice_mask_for_free(struct mm_struct *mm, struct slice_mask *ret,
>> if (!slice_low_has_vma(mm, i))
>> ret->low_slices |= 1u << i;
>>
>> - if (high_limit <= SLICE_LOW_TOP)
>> + if (slice_addr_is_low(high_limit - 1))
>
> Is high_limit ever going to be 0 ?
See slice_get_unmapped_area(), high_limit will never be 0.
Christophe
>
>> return;
>>
>> for (i = 0; i < GET_HIGH_SLICE_INDEX(high_limit); i++)
>> @@ -183,7 +190,7 @@ static bool slice_check_range_fits(struct mm_struct *mm,
>> unsigned long end = start + len - 1;
>> u64 low_slices = 0;
>>
>> - if (start < SLICE_LOW_TOP) {
>> + if (slice_addr_is_low(start)) {
>> unsigned long mend = min(end,
>> (unsigned long)(SLICE_LOW_TOP - 1));
>>
>> @@ -193,7 +200,7 @@ static bool slice_check_range_fits(struct mm_struct *mm,
>> if ((low_slices & available->low_slices) != low_slices)
>> return false;
>>
>> - if (SLICE_NUM_HIGH && ((start + len) > SLICE_LOW_TOP)) {
>> + if (SLICE_NUM_HIGH && !slice_addr_is_low(end)) {
>> unsigned long start_index = GET_HIGH_SLICE_INDEX(start);
>> unsigned long align_end = ALIGN(end, (1UL << SLICE_HIGH_SHIFT));
>> unsigned long count = GET_HIGH_SLICE_INDEX(align_end) - start_index;
>> @@ -304,7 +311,7 @@ static bool slice_scan_available(unsigned long addr,
>> int end, unsigned long *boundary_addr)
>> {
>> unsigned long slice;
>> - if (addr < SLICE_LOW_TOP) {
>> + if (slice_addr_is_low(addr)) {
>> slice = GET_LOW_SLICE_INDEX(addr);
>> *boundary_addr = (slice + end) << SLICE_LOW_SHIFT;
>> return !!(available->low_slices & (1u << slice));
>> @@ -707,7 +714,7 @@ unsigned int get_slice_psize(struct mm_struct *mm, unsigned long addr)
>>
>> VM_BUG_ON(radix_enabled());
>>
>> - if (addr < SLICE_LOW_TOP) {
>> + if (slice_addr_is_low(addr)) {
>> psizes = mm->context.low_slices_psize;
>> index = GET_LOW_SLICE_INDEX(addr);
>> } else {
>> --
>> 2.13.3
>>
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