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[2003:cb:c708:9d00:edd9:835b:4bfb:2ce3]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-436611ea3e0sm53634835e9.7.2024.12.20.10.52.44 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 20 Dec 2024 10:52:46 -0800 (PST) Message-ID: Date: Fri, 20 Dec 2024 19:52:43 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 15/25] huge_memory: Add vmf_insert_folio_pud() To: Alistair Popple , akpm@linux-foundation.org, dan.j.williams@intel.com, linux-mm@kvack.org Cc: lina@asahilina.net, zhang.lyra@gmail.com, gerald.schaefer@linux.ibm.com, vishal.l.verma@intel.com, dave.jiang@intel.com, logang@deltatee.com, bhelgaas@google.com, jack@suse.cz, jgg@ziepe.ca, catalin.marinas@arm.com, will@kernel.org, mpe@ellerman.id.au, npiggin@gmail.com, dave.hansen@linux.intel.com, ira.weiny@intel.com, willy@infradead.org, djwong@kernel.org, tytso@mit.edu, linmiaohe@huawei.com, peterx@redhat.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, nvdimm@lists.linux.dev, linux-cxl@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org, jhubbard@nvidia.com, hch@lst.de, david@fromorbit.com References: <03cb3c24f10818c0780a08509628893ab460e5d1.1734407924.git-series.apopple@nvidia.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 6640C4000B X-Stat-Signature: 5dk9qszinf84mncrypqr9k1knd8fopru X-Rspam-User: X-HE-Tag: 1734720733-538236 X-HE-Meta: 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 r5Mzd7hR 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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 17.12.24 06:12, Alistair Popple wrote: > Currently DAX folio/page reference counts are managed differently to > normal pages. To allow these to be managed the same as normal pages > introduce vmf_insert_folio_pud. This will map the entire PUD-sized folio > and take references as it would for a normally mapped page. > > This is distinct from the current mechanism, vmf_insert_pfn_pud, which > simply inserts a special devmap PUD entry into the page table without > holding a reference to the page for the mapping. > > Signed-off-by: Alistair Popple > --- > include/linux/huge_mm.h | 11 +++++- > mm/huge_memory.c | 96 ++++++++++++++++++++++++++++++++++++------ > 2 files changed, 95 insertions(+), 12 deletions(-) > > diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h > index 93e509b..012137b 100644 > --- a/include/linux/huge_mm.h > +++ b/include/linux/huge_mm.h > @@ -39,6 +39,7 @@ int change_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, > > vm_fault_t vmf_insert_pfn_pmd(struct vm_fault *vmf, pfn_t pfn, bool write); > vm_fault_t vmf_insert_pfn_pud(struct vm_fault *vmf, pfn_t pfn, bool write); > +vm_fault_t vmf_insert_folio_pud(struct vm_fault *vmf, struct folio *folio, bool write); > > enum transparent_hugepage_flag { > TRANSPARENT_HUGEPAGE_UNSUPPORTED, > @@ -458,6 +459,11 @@ static inline bool is_huge_zero_pmd(pmd_t pmd) > return pmd_present(pmd) && READ_ONCE(huge_zero_pfn) == pmd_pfn(pmd); > } > > +static inline bool is_huge_zero_pud(pud_t pud) > +{ > + return false; > +} > + > struct folio *mm_get_huge_zero_folio(struct mm_struct *mm); > void mm_put_huge_zero_folio(struct mm_struct *mm); > > @@ -604,6 +610,11 @@ static inline bool is_huge_zero_pmd(pmd_t pmd) > return false; > } > > +static inline bool is_huge_zero_pud(pud_t pud) > +{ > + return false; > +} > + I'm really not a fan of these, because I assume we will never ever implement these any time soon. (who will waste 1 GiG or more on faster reading of 0s?) > static inline void mm_put_huge_zero_folio(struct mm_struct *mm) > { > return; > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index 120cd2c..5081808 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -1482,19 +1482,17 @@ static void insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr, > struct mm_struct *mm = vma->vm_mm; > pgprot_t prot = vma->vm_page_prot; > pud_t entry; > - spinlock_t *ptl; > > - ptl = pud_lock(mm, pud); > if (!pud_none(*pud)) { > if (write) { > if (WARN_ON_ONCE(pud_pfn(*pud) != pfn_t_to_pfn(pfn))) > - goto out_unlock; > + return; > entry = pud_mkyoung(*pud); > entry = maybe_pud_mkwrite(pud_mkdirty(entry), vma); > if (pudp_set_access_flags(vma, addr, pud, entry, 1)) > update_mmu_cache_pud(vma, addr, pud); > } > - goto out_unlock; > + return; > } > > entry = pud_mkhuge(pfn_t_pud(pfn, prot)); > @@ -1508,9 +1506,6 @@ static void insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr, > } > set_pud_at(mm, addr, pud, entry); > update_mmu_cache_pud(vma, addr, pud); > - > -out_unlock: > - spin_unlock(ptl); > } > > /** > @@ -1528,6 +1523,7 @@ vm_fault_t vmf_insert_pfn_pud(struct vm_fault *vmf, pfn_t pfn, bool write) > unsigned long addr = vmf->address & PUD_MASK; > struct vm_area_struct *vma = vmf->vma; > pgprot_t pgprot = vma->vm_page_prot; > + spinlock_t *ptl; > > /* > * If we had pud_special, we could avoid all these restrictions, > @@ -1545,10 +1541,55 @@ vm_fault_t vmf_insert_pfn_pud(struct vm_fault *vmf, pfn_t pfn, bool write) > > track_pfn_insert(vma, &pgprot, pfn); > > + ptl = pud_lock(vma->vm_mm, vmf->pud); > insert_pfn_pud(vma, addr, vmf->pud, pfn, write); > + spin_unlock(ptl); > + > return VM_FAULT_NOPAGE; > } > EXPORT_SYMBOL_GPL(vmf_insert_pfn_pud); > + > +/** > + * vmf_insert_folio_pud - insert a pud size folio mapped by a pud entry > + * @vmf: Structure describing the fault > + * @pfn: pfn of the page to insert > + * @write: whether it's a write fault > + * > + * Return: vm_fault_t value. > + */ > +vm_fault_t vmf_insert_folio_pud(struct vm_fault *vmf, struct folio *folio, bool write) > +{ > + struct vm_area_struct *vma = vmf->vma; > + unsigned long addr = vmf->address & PUD_MASK; > + pfn_t pfn = pfn_to_pfn_t(folio_pfn(folio)); > + pud_t *pud = vmf->pud; > + pgprot_t prot = vma->vm_page_prot; See below, pfn, prot and page can likely go. > + struct mm_struct *mm = vma->vm_mm; > + spinlock_t *ptl; > + struct page *page; > + > + if (addr < vma->vm_start || addr >= vma->vm_end) > + return VM_FAULT_SIGBUS; > + > + if (WARN_ON_ONCE(folio_order(folio) != PUD_ORDER)) > + return VM_FAULT_SIGBUS; > + > + track_pfn_insert(vma, &prot, pfn); Oh, why is that required? We are inserting a folio and start messing with VM_PAT on x86 that only applies to VM_PFNMAP mappings? :) > + > + ptl = pud_lock(mm, pud); > + if (pud_none(*vmf->pud)) { > + page = pfn_t_to_page(pfn); Why are we suddenly working with that pfn_t whichcraft? :) > + folio = page_folio(page); Ehm, you got the folio ... passed into this function? Why can't that simply be folio_get(folio); folio_add_file_rmap_pud(folio, folio_page(folio, 0), vma); > + folio_get(folio); > + folio_add_file_rmap_pud(folio, page, vma); > + add_mm_counter(mm, mm_counter_file(folio), HPAGE_PUD_NR); > + } > + insert_pfn_pud(vma, addr, vmf->pud, pfn, write); > + spin_unlock(ptl); > + > + return VM_FAULT_NOPAGE; > +} > +EXPORT_SYMBOL_GPL(vmf_insert_folio_pud); > #endif /* CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD */ > > void touch_pmd(struct vm_area_struct *vma, unsigned long addr, > @@ -2146,7 +2187,8 @@ int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, > zap_deposited_table(tlb->mm, pmd); > spin_unlock(ptl); > } else if (is_huge_zero_pmd(orig_pmd)) { > - zap_deposited_table(tlb->mm, pmd); > + if (!vma_is_dax(vma) || arch_needs_pgtable_deposit()) > + zap_deposited_table(tlb->mm, pmd); > spin_unlock(ptl); > } else { > struct folio *folio = NULL; > @@ -2634,12 +2676,24 @@ int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma, > orig_pud = pudp_huge_get_and_clear_full(vma, addr, pud, tlb->fullmm); > arch_check_zapped_pud(vma, orig_pud); > tlb_remove_pud_tlb_entry(tlb, pud, addr); > - if (vma_is_special_huge(vma)) { > + if (!vma_is_dax(vma) && vma_is_special_huge(vma)) { > spin_unlock(ptl); > /* No zero page support yet */ > } else { > - /* No support for anonymous PUD pages yet */ > - BUG(); > + struct page *page = NULL; > + struct folio *folio; > + > + /* No support for anonymous PUD pages or migration yet */ > + BUG_ON(vma_is_anonymous(vma) || !pud_present(orig_pud)); VM_WARN_ON_ONCE(). > + > + page = pud_page(orig_pud); > + folio = page_folio(page); > + folio_remove_rmap_pud(folio, page, vma); > + VM_BUG_ON_PAGE(!PageHead(page), page); Please drop that or so something like VM_WARN_ON_ONCE(page != folio_page(folio, 0)); > + add_mm_counter(tlb->mm, mm_counter_file(folio), -HPAGE_PUD_NR); > + > + spin_unlock(ptl); > + tlb_remove_page_size(tlb, page, HPAGE_PUD_SIZE); > } > return 1; > } > @@ -2647,6 +2701,8 @@ int zap_huge_pud(struct mmu_gather *tlb, struct vm_area_struct *vma, > static void __split_huge_pud_locked(struct vm_area_struct *vma, pud_t *pud, > unsigned long haddr) > { > + pud_t old_pud; > + > VM_BUG_ON(haddr & ~HPAGE_PUD_MASK); > VM_BUG_ON_VMA(vma->vm_start > haddr, vma); > VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PUD_SIZE, vma); > @@ -2654,7 +2710,23 @@ static void __split_huge_pud_locked(struct vm_area_struct *vma, pud_t *pud, > > count_vm_event(THP_SPLIT_PUD); > > - pudp_huge_clear_flush(vma, haddr, pud); > + old_pud = pudp_huge_clear_flush(vma, haddr, pud); > + if (is_huge_zero_pud(old_pud)) > + return; > + > + if (vma_is_dax(vma)) { Maybe you want if (!vma_is_dax(vma)) return; To then reduce alignment. I suspect all other splitting code (besides anon memory) will want to do the same thing here in the future. -- Cheers, David / dhildenb