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Mon, 17 Apr 2023 13:52:47 -0700 (PDT) Received: from fedora.hsd1.ca.comcast.net ([2601:644:937f:7f20::c139]) by smtp.googlemail.com with ESMTPSA id h7-20020a17090ac38700b0022335f1dae2sm7609707pjt.22.2023.04.17.13.52.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 17 Apr 2023 13:52:47 -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)" Subject: [PATCH 02/33] s390: Use pt_frag_refcount for pagetables Date: Mon, 17 Apr 2023 13:50:17 -0700 Message-Id: <20230417205048.15870-3-vishal.moola@gmail.com> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20230417205048.15870-1-vishal.moola@gmail.com> References: <20230417205048.15870-1-vishal.moola@gmail.com> MIME-Version: 1.0 X-Rspamd-Queue-Id: 191732001A X-Stat-Signature: f8bjmnen7tafcid3z5b1a6xc6unso7ru X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1681764768-104553 X-HE-Meta: U2FsdGVkX1+7MOO+YwtUPKln1QuKLf9O2BPuAOhfDhdenB+WhkupDd2qWSgjUiClu1tlxE60XxWbLIER9OyjSFeb6zYW9+JA4oZttVvSXLVC/Gj/2PCBC1ILMtAlO2D+/KlxmHQFOYvMmVdFGrg5fGtDMYvz6m9VhEGBi1CJp9pdTrIQ/0gQJzTBnoKFRCwv7BeLaq82plo0FYHIzGpvNq7EH7X9+oh/cKoxRUzpgJIka2JcDjf4mANGC9i1ZkYPDUHVXze5CoxAlyQ+oS2RjteUm+nmdq3ql8zfPYph9ojnF+s4y3ANPFTE4UepNuF147+GyYx+Aseo1HlzRW6VLKKZ9U62H//nmGy9HB7nSm0WDHZ9uK611cjLDAZCZaJKmK+lC2bMoNi55PgmuqKmP6NJ4TDW/p6aIQ8dqIAPlvmNNTei+3FXOawB1Op/os991BZSr91DRRyvPNlVEqYhyYQtsq5yHJvfmQkXMLkLQwyQcjRICyeQvAo/YblrJRvpx4jj4uY6Gf1eaJaGhBrzFEC9UmLEg31iwmSyCcbf+VKAjTBkVbVoDiWibt9UfpTyRhhhGOUFF0Ecf6N7cQAHAAY7y5EcRd0XQed68UdssXK2pLZIsjtK99ufy7GHBdRCYU847MP6y7ipThtl3qVy6uJlwLRlCnN5ncYiGFN5qtxcLcgRoKJd8bfKmIZqiyAgnBt6plv1U5aHNUAgGztKDUY3KlT5LBs6i0eK6Q7WB3TrUWc/7DFs07oO5fEVoTFgMp8tDAx2EjTC4tHl3vaOTvrcADpgWhgJD/mMsBtUwb/riyDnv0609StiX7MDADJN859oglBWltVe0H8IDUeJLFVtA33dISSdNKQMFd+E152dbErvoq+XKQdmcmjNbKDqzizaKC/zc61OwFRN1UNa8IZV/Oc4bJReOcdIBeZrTzs+sBAaHcgq0LtQASyeykr/Ags3NG+IUIKUsGZPNEb cXLdxLbv 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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; }