From: Will Deacon <will@kernel.org> To: linux-kernel@vger.kernel.org Cc: sparclinux@vger.kernel.org, Will Deacon <will@kernel.org>, Peter Zijlstra <peterz@infradead.org>, "David S . Miller" <davem@davemloft.net>, Guenter Roeck <linux@roeck-us.net>, Mike Rapoport <rppt@kernel.org>, kernel-team@android.com Subject: [PATCH 3/3] sparc32: mm: Only call ctor()/dtor() functions for first and last user Date: Tue, 26 May 2020 18:33:02 +0100 [thread overview] Message-ID: <20200526173302.377-4-will@kernel.org> (raw) In-Reply-To: <20200526173302.377-1-will@kernel.org> The SRMMU page-table allocator allocates multiple PTE tables per page, since they are only 1K in size. However, this means that calls to pgtable_pte_page_{ctor,dtor}() must be serialised and performed only by the first and last page-table allocation for the page respectively. Use the page reference count to track how many PTE tables we have allocated for a given page returned by the SRMMU allocator and only call the ctor()/dtor() functions for the first and last user respectively. Cc: David S. Miller <davem@davemloft.net> Fixes: 8c8f3156dd40 ("sparc32: mm: Reduce allocation size for PMD and PTE tables") Signed-off-by: Will Deacon <will@kernel.org> --- arch/sparc/mm/srmmu.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) diff --git a/arch/sparc/mm/srmmu.c b/arch/sparc/mm/srmmu.c index 589370a21b12..116d19a390f2 100644 --- a/arch/sparc/mm/srmmu.c +++ b/arch/sparc/mm/srmmu.c @@ -364,9 +364,13 @@ pgtable_t pte_alloc_one(struct mm_struct *mm) if ((ptep = pte_alloc_one_kernel(mm)) == 0) return NULL; page = pfn_to_page(__nocache_pa((unsigned long)ptep) >> PAGE_SHIFT); - if (!pgtable_pte_page_ctor(page)) { - return NULL; + spin_lock(&mm->page_table_lock); + if (page_ref_inc_return(page) == 2 && !pgtable_pte_page_ctor(page)) { + page_ref_dec(page); + ptep = NULL; } + spin_unlock(&mm->page_table_lock); + return ptep; } @@ -375,7 +379,11 @@ void pte_free(struct mm_struct *mm, pgtable_t ptep) struct page *page; page = pfn_to_page(__nocache_pa((unsigned long)ptep) >> PAGE_SHIFT); - pgtable_pte_page_dtor(page); + spin_lock(&mm->page_table_lock); + if (page_ref_dec_return(page) == 1) + pgtable_pte_page_dtor(page); + spin_unlock(&mm->page_table_lock); + srmmu_free_nocache(ptep, SRMMU_PTE_TABLE_SIZE); } -- 2.27.0.rc0.183.gde8f92d652-goog
WARNING: multiple messages have this Message-ID (diff)
From: Will Deacon <will@kernel.org> To: linux-kernel@vger.kernel.org Cc: sparclinux@vger.kernel.org, Will Deacon <will@kernel.org>, Peter Zijlstra <peterz@infradead.org>, "David S . Miller" <davem@davemloft.net>, Guenter Roeck <linux@roeck-us.net>, Mike Rapoport <rppt@kernel.org>, kernel-team@android.com Subject: [PATCH 3/3] sparc32: mm: Only call ctor()/dtor() functions for first and last user Date: Tue, 26 May 2020 17:33:02 +0000 [thread overview] Message-ID: <20200526173302.377-4-will@kernel.org> (raw) In-Reply-To: <20200526173302.377-1-will@kernel.org> The SRMMU page-table allocator allocates multiple PTE tables per page, since they are only 1K in size. However, this means that calls to pgtable_pte_page_{ctor,dtor}() must be serialised and performed only by the first and last page-table allocation for the page respectively. Use the page reference count to track how many PTE tables we have allocated for a given page returned by the SRMMU allocator and only call the ctor()/dtor() functions for the first and last user respectively. Cc: David S. Miller <davem@davemloft.net> Fixes: 8c8f3156dd40 ("sparc32: mm: Reduce allocation size for PMD and PTE tables") Signed-off-by: Will Deacon <will@kernel.org> --- arch/sparc/mm/srmmu.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) diff --git a/arch/sparc/mm/srmmu.c b/arch/sparc/mm/srmmu.c index 589370a21b12..116d19a390f2 100644 --- a/arch/sparc/mm/srmmu.c +++ b/arch/sparc/mm/srmmu.c @@ -364,9 +364,13 @@ pgtable_t pte_alloc_one(struct mm_struct *mm) if ((ptep = pte_alloc_one_kernel(mm)) = 0) return NULL; page = pfn_to_page(__nocache_pa((unsigned long)ptep) >> PAGE_SHIFT); - if (!pgtable_pte_page_ctor(page)) { - return NULL; + spin_lock(&mm->page_table_lock); + if (page_ref_inc_return(page) = 2 && !pgtable_pte_page_ctor(page)) { + page_ref_dec(page); + ptep = NULL; } + spin_unlock(&mm->page_table_lock); + return ptep; } @@ -375,7 +379,11 @@ void pte_free(struct mm_struct *mm, pgtable_t ptep) struct page *page; page = pfn_to_page(__nocache_pa((unsigned long)ptep) >> PAGE_SHIFT); - pgtable_pte_page_dtor(page); + spin_lock(&mm->page_table_lock); + if (page_ref_dec_return(page) = 1) + pgtable_pte_page_dtor(page); + spin_unlock(&mm->page_table_lock); + srmmu_free_nocache(ptep, SRMMU_PTE_TABLE_SIZE); } -- 2.27.0.rc0.183.gde8f92d652-goog
next prev parent reply other threads:[~2020-05-26 17:33 UTC|newest] Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-05-26 17:32 [PATCH 0/3] sparc32 SRMMU fixes for SMP Will Deacon 2020-05-26 17:32 ` Will Deacon 2020-05-26 17:33 ` [PATCH 1/3] sparc32: mm: Don't try to free page-table pages if ctor() fails Will Deacon 2020-05-26 17:33 ` Will Deacon 2020-05-26 17:33 ` [PATCH 2/3] sparc32: mm: Disable SPLIT_PTLOCK_CPUS Will Deacon 2020-05-26 17:33 ` Will Deacon 2020-05-26 17:33 ` Will Deacon [this message] 2020-05-26 17:33 ` [PATCH 3/3] sparc32: mm: Only call ctor()/dtor() functions for first and last user Will Deacon 2020-06-03 1:46 ` [PATCH 0/3] sparc32 SRMMU fixes for SMP David Miller 2020-06-03 1:46 ` David Miller
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