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Message-ID: <CA+7wUszwUKjdQzdekaE-CJ1_d9JR9HCz5od1L390EMpRbfTfng@mail.gmail.com>
Date: Fri, 22 Jun 2018 16:55:20 +0200
From: Mathieu Malaterre <malat@...ian.org>
To: Christophe LEROY <christophe.leroy@....fr>
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
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 ?
> 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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