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Mon, 01 May 2023 12:28:38 -0700 (PDT) Received: from fedora.hsd1.ca.comcast.net ([2601:644:937f:7f20::9a2c]) by smtp.googlemail.com with ESMTPSA id u8-20020a170902bf4800b0019c13d032d8sm18175622pls.253.2023.05.01.12.28.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 01 May 2023 12:28:38 -0700 (PDT) From: "Vishal Moola (Oracle)" To: Andrew Morton , Matthew Wilcox Cc: linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-csky@vger.kernel.org, linux-hexagon@vger.kernel.org, loongarch@lists.linux.dev, linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org, linux-openrisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-um@lists.infradead.org, xen-devel@lists.xenproject.org, kvm@vger.kernel.org, "Vishal Moola (Oracle)" , David Hildenbrand , Claudio Imbrenda Subject: [PATCH v2 03/34] s390: Use pt_frag_refcount for pagetables Date: Mon, 1 May 2023 12:27:58 -0700 Message-Id: <20230501192829.17086-4-vishal.moola@gmail.com> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20230501192829.17086-1-vishal.moola@gmail.com> References: <20230501192829.17086-1-vishal.moola@gmail.com> MIME-Version: 1.0 X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: E3E0F180005 X-Rspam-User: X-Stat-Signature: hxffytdtu1y3hro6hy8oo7fczs3hpwto X-HE-Tag: 1682969319-701198 X-HE-Meta: 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 Vk6OIMbI 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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: s390 currently uses _refcount to identify fragmented page tables. The page table struct already has a member pt_frag_refcount used by powerpc, so have s390 use that instead of the _refcount field as well. This improves the safety for _refcount and the page table tracking. This also allows us to simplify the tracking since we can once again use the lower byte of pt_frag_refcount instead of the upper byte of _refcount. Signed-off-by: Vishal Moola (Oracle) --- arch/s390/mm/pgalloc.c | 38 +++++++++++++++----------------------- 1 file changed, 15 insertions(+), 23 deletions(-) diff --git a/arch/s390/mm/pgalloc.c b/arch/s390/mm/pgalloc.c index 66ab68db9842..6b99932abc66 100644 --- a/arch/s390/mm/pgalloc.c +++ b/arch/s390/mm/pgalloc.c @@ -182,20 +182,17 @@ void page_table_free_pgste(struct page *page) * As follows from the above, no unallocated or fully allocated parent * pages are contained in mm_context_t::pgtable_list. * - * The upper byte (bits 24-31) of the parent page _refcount is used + * The lower byte (bits 0-7) of the parent page pt_frag_refcount is used * for tracking contained 2KB-pgtables and has the following format: * * PP AA - * 01234567 upper byte (bits 24-31) of struct page::_refcount + * 01234567 upper byte (bits 0-7) of struct page::pt_frag_refcount * || || * || |+--- upper 2KB-pgtable is allocated * || +---- lower 2KB-pgtable is allocated * |+------- upper 2KB-pgtable is pending for removal * +-------- lower 2KB-pgtable is pending for removal * - * (See commit 620b4e903179 ("s390: use _refcount for pgtables") on why - * using _refcount is possible). - * * When 2KB-pgtable is allocated the corresponding AA bit is set to 1. * The parent page is either: * - added to mm_context_t::pgtable_list in case the second half of the @@ -243,11 +240,12 @@ unsigned long *page_table_alloc(struct mm_struct *mm) if (!list_empty(&mm->context.pgtable_list)) { page = list_first_entry(&mm->context.pgtable_list, struct page, lru); - mask = atomic_read(&page->_refcount) >> 24; + mask = atomic_read(&page->pt_frag_refcount); /* * The pending removal bits must also be checked. * Failure to do so might lead to an impossible - * value of (i.e 0x13 or 0x23) written to _refcount. + * value of (i.e 0x13 or 0x23) written to + * pt_frag_refcount. * Such values violate the assumption that pending and * allocation bits are mutually exclusive, and the rest * of the code unrails as result. That could lead to @@ -259,8 +257,8 @@ unsigned long *page_table_alloc(struct mm_struct *mm) bit = mask & 1; /* =1 -> second 2K */ if (bit) table += PTRS_PER_PTE; - atomic_xor_bits(&page->_refcount, - 0x01U << (bit + 24)); + atomic_xor_bits(&page->pt_frag_refcount, + 0x01U << bit); list_del(&page->lru); } } @@ -281,12 +279,12 @@ unsigned long *page_table_alloc(struct mm_struct *mm) table = (unsigned long *) page_to_virt(page); if (mm_alloc_pgste(mm)) { /* Return 4K page table with PGSTEs */ - atomic_xor_bits(&page->_refcount, 0x03U << 24); + atomic_xor_bits(&page->pt_frag_refcount, 0x03U); memset64((u64 *)table, _PAGE_INVALID, PTRS_PER_PTE); memset64((u64 *)table + PTRS_PER_PTE, 0, PTRS_PER_PTE); } else { /* Return the first 2K fragment of the page */ - atomic_xor_bits(&page->_refcount, 0x01U << 24); + atomic_xor_bits(&page->pt_frag_refcount, 0x01U); memset64((u64 *)table, _PAGE_INVALID, 2 * PTRS_PER_PTE); spin_lock_bh(&mm->context.lock); list_add(&page->lru, &mm->context.pgtable_list); @@ -323,22 +321,19 @@ void page_table_free(struct mm_struct *mm, unsigned long *table) * will happen outside of the critical section from this * function or from __tlb_remove_table() */ - mask = atomic_xor_bits(&page->_refcount, 0x11U << (bit + 24)); - mask >>= 24; + mask = atomic_xor_bits(&page->pt_frag_refcount, 0x11U << bit); if (mask & 0x03U) list_add(&page->lru, &mm->context.pgtable_list); else list_del(&page->lru); spin_unlock_bh(&mm->context.lock); - mask = atomic_xor_bits(&page->_refcount, 0x10U << (bit + 24)); - mask >>= 24; + mask = atomic_xor_bits(&page->pt_frag_refcount, 0x10U << bit); if (mask != 0x00U) return; half = 0x01U << bit; } else { half = 0x03U; - mask = atomic_xor_bits(&page->_refcount, 0x03U << 24); - mask >>= 24; + mask = atomic_xor_bits(&page->pt_frag_refcount, 0x03U); } page_table_release_check(page, table, half, mask); @@ -368,8 +363,7 @@ void page_table_free_rcu(struct mmu_gather *tlb, unsigned long *table, * outside of the critical section from __tlb_remove_table() or from * page_table_free() */ - mask = atomic_xor_bits(&page->_refcount, 0x11U << (bit + 24)); - mask >>= 24; + mask = atomic_xor_bits(&page->pt_frag_refcount, 0x11U << bit); if (mask & 0x03U) list_add_tail(&page->lru, &mm->context.pgtable_list); else @@ -391,14 +385,12 @@ void __tlb_remove_table(void *_table) return; case 0x01U: /* lower 2K of a 4K page table */ case 0x02U: /* higher 2K of a 4K page table */ - mask = atomic_xor_bits(&page->_refcount, mask << (4 + 24)); - mask >>= 24; + mask = atomic_xor_bits(&page->pt_frag_refcount, mask << 4); if (mask != 0x00U) return; break; case 0x03U: /* 4K page table with pgstes */ - mask = atomic_xor_bits(&page->_refcount, 0x03U << 24); - mask >>= 24; + mask = atomic_xor_bits(&page->pt_frag_refcount, 0x03U); break; }