Commit 1996d47a authored May 26, 2020 by Will Deacon Committed by David S. Miller Jun 02, 2020

sparc32: mm: Only call ctor()/dtor() functions for first and last user

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: 8c8f3156 ("sparc32: mm: Reduce allocation size for PMD and PTE tables")
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 60bccaa6

arch/sparc/mm/srmmu.c

+11 −3

Original line number	Diff line number	Diff line
		@@ -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);
		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);
		}

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