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Howlett" , linux-kernel@vger.kernel.org, linux-mm@kvack.org, kvm@vger.kernel.org, Andrew Morton , Alex Williamson , Zi Yan , Jason Gunthorpe , Alex Mastro , David Hildenbrand , Nico Pache , Huacai Chen , Thomas Bogendoerfer , Muchun Song , Oscar Salvador , loongarch@lists.linux.dev, linux-mips@vger.kernel.org Subject: Re: [PATCH 2/5] mm/hugetlb: Remove prepare_hugepage_range() Message-ID: References: <20250613134111.469884-1-peterx@redhat.com> <20250613134111.469884-3-peterx@redhat.com> <4rypovqoa4j6f4fyfqzrm5xeiv3dng5hc5dlfhmnehkydk6gcd@z6f3k3joaoli> MIME-Version: 1.0 In-Reply-To: <4rypovqoa4j6f4fyfqzrm5xeiv3dng5hc5dlfhmnehkydk6gcd@z6f3k3joaoli> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: vd8HcU3gitmjWVPObpnWrOfIDIRQR05UpFW5Vey7Gbc_1750194454 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: BDE821C0005 X-Stat-Signature: tm5dnxyskp48kqn37ozhafckhpe49ehb X-Rspam-User: X-HE-Tag: 1750194456-3241 X-HE-Meta: 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 u7reXLWi 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 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: List-Subscribe: List-Unsubscribe: On Sat, Jun 14, 2025 at 12:11:22AM -0400, Liam R. Howlett wrote: > * Peter Xu [691231 23:00]: > > Only mips and loongarch implemented this API, however what it does was > > checking against stack overflow for either len or addr. That's already > > done in arch's arch_get_unmapped_area*() functions, hence not needed. > > I'm not as confident.. > > > > > It means the whole API is pretty much obsolete at least now, remove it > > completely. > > > > Cc: Huacai Chen > > Cc: Thomas Bogendoerfer > > Cc: Muchun Song > > Cc: Oscar Salvador > > Cc: loongarch@lists.linux.dev > > Cc: linux-mips@vger.kernel.org > > Signed-off-by: Peter Xu > > --- > > arch/loongarch/include/asm/hugetlb.h | 14 -------------- > > arch/mips/include/asm/hugetlb.h | 14 -------------- > > fs/hugetlbfs/inode.c | 8 ++------ > > include/asm-generic/hugetlb.h | 8 -------- > > include/linux/hugetlb.h | 6 ------ > > 5 files changed, 2 insertions(+), 48 deletions(-) > > > > diff --git a/arch/loongarch/include/asm/hugetlb.h b/arch/loongarch/include/asm/hugetlb.h > > index 4dc4b3e04225..ab68b594f889 100644 > > --- a/arch/loongarch/include/asm/hugetlb.h > > +++ b/arch/loongarch/include/asm/hugetlb.h > > @@ -10,20 +10,6 @@ > > > > uint64_t pmd_to_entrylo(unsigned long pmd_val); > > > > -#define __HAVE_ARCH_PREPARE_HUGEPAGE_RANGE > > -static inline int prepare_hugepage_range(struct file *file, > > - unsigned long addr, > > - unsigned long len) > > -{ > > - unsigned long task_size = STACK_TOP; > > - > > - if (len > task_size) > > - return -ENOMEM; > > - if (task_size - len < addr) > > - return -EINVAL; > > - return 0; > > -} > > - > > #define __HAVE_ARCH_HUGE_PTE_CLEAR > > static inline void huge_pte_clear(struct mm_struct *mm, unsigned long addr, > > pte_t *ptep, unsigned long sz) > > diff --git a/arch/mips/include/asm/hugetlb.h b/arch/mips/include/asm/hugetlb.h > > index fbc71ddcf0f6..8c460ce01ffe 100644 > > --- a/arch/mips/include/asm/hugetlb.h > > +++ b/arch/mips/include/asm/hugetlb.h > > @@ -11,20 +11,6 @@ > > > > #include > > > > -#define __HAVE_ARCH_PREPARE_HUGEPAGE_RANGE > > -static inline int prepare_hugepage_range(struct file *file, > > - unsigned long addr, > > - unsigned long len) > > -{ > > - unsigned long task_size = STACK_TOP; > > arch/mips/include/asm/processor.h:#define STACK_TOP mips_stack_top() > > > unsigned long mips_stack_top(void) > { > unsigned long top = TASK_SIZE & PAGE_MASK; > > if (IS_ENABLED(CONFIG_MIPS_FP_SUPPORT)) { > /* One page for branch delay slot "emulation" */ > top -= PAGE_SIZE; > } > > /* Space for the VDSO, data page & GIC user page */ > top -= PAGE_ALIGN(current->thread.abi->vdso->size); > top -= PAGE_SIZE; > top -= mips_gic_present() ? PAGE_SIZE : 0; > > /* Space for cache colour alignment */ > if (cpu_has_dc_aliases) > top -= shm_align_mask + 1; > > /* Space to randomize the VDSO base */ > if (current->flags & PF_RANDOMIZE) > top -= VDSO_RANDOMIZE_SIZE; > > return top; > } > > This seems different than TASK_SIZE. > > Code is from: > commit ea7e0480a4b695d0aa6b3fa99bd658a003122113 > Author: Paul Burton > Date: Tue Sep 25 15:51:26 2018 -0700 > > > > - if (len > task_size) > > - return -ENOMEM; > > - if (task_size - len < addr) > > - return -EINVAL; > > - return 0; > > -} > > - > > Unfortunately, the commit message for the addition of this code are not > helpful. > > commit 50a41ff292fafe1e937102be23464b54fed8b78c > Author: David Daney > Date: Wed May 27 17:47:42 2009 -0700 > > ... But the dates are helpful. This code used to use: > #define STACK_TOP ((TASK_SIZE & PAGE_MASK) - PAGE_SIZE) > > It's not exactly task size either. > > I don't think this is an issue to remove this check because the overflow > should be caught later (or trigger the opposite search). But it's not > clear why STACK_TOP was done in the first place.. Maybe just because we > know the overflow here would be an issue later, but then we'd avoid the > opposite search - and maybe that's the point? > > Either way, your comment about the same check existing doesn't seem > correct. I will fix up the commit message to mention both archs: Only mips and loongarch implemented this API, however what it does was checking against stack overflow for either len or addr. That's already done in arch's arch_get_unmapped_area*() functions, even though it may not be 100% identical checks. For example, for both of the architectures, there will be a trivial difference on how stack top was defined. The old code uses STACK_TOP which may be slightly smaller than TASK_SIZE on either of them, but the hope is that shouldn't be a problem. It means the whole API is pretty much obsolete at least now, remove it completely. > > I haven't checked loong arch, but I'd be willing to wager this was just > cloned mips code... because this happens so much. They define STACK_TOP differently, but AFAIU there're some duplications in pattern of the two archs. Please let me know if the fixed commit message works for you above, thanks. -- Peter Xu