Commit 9ad9718b authored Aug 06, 2020 by Wei Yang Committed by Linus Torvalds Aug 07, 2020

mm/mremap: calculate extent in one place



Page tables is moved on the base of PMD.  This requires both source and
destination range should meet the requirement.

Current code works well since move_huge_pmd() and move_normal_pmd() would
check old_addr and new_addr again.  And then return to move_ptes() if the
either of them is not aligned.

Instead of calculating the extent separately, it is better to calculate in
one place, so we know it is not necessary to try move pmd.  By doing so,
the logic seems a little clear.

Signed-off-by: Wei Yang <richard.weiyang@linux.alibaba.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Tested-by: Dmitry Osipenko <digetx@gmail.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Thomas Hellstrom <thellstrom@vmware.com>
Cc: Thomas Hellstrom (VMware) <thomas_os@shipmail.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yang Shi <yang.shi@linux.alibaba.com>
Link: http://lkml.kernel.org/r/20200708095028.41706-3-richard.weiyang@linux.alibaba.com


Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent b8aa9d9d

mm/mremap.c

+3 −3

Original line number	Diff line number	Diff line
		@@ -277,6 +277,9 @@ unsigned long move_page_tables(struct vm_area_struct *vma,
		extent = next - old_addr;
		if (extent > old_end - old_addr)
		extent = old_end - old_addr;
		next = (new_addr + PMD_SIZE) & PMD_MASK;
		if (extent > next - new_addr)
		extent = next - new_addr;
		old_pmd = get_old_pmd(vma->vm_mm, old_addr);
		if (!old_pmd)
		continue;
		@@ -320,9 +323,6 @@ unsigned long move_page_tables(struct vm_area_struct *vma,

		if (pte_alloc(new_vma->vm_mm, new_pmd))
		break;
		next = (new_addr + PMD_SIZE) & PMD_MASK;
		if (extent > next - new_addr)
		extent = next - new_addr;
		move_ptes(vma, old_pmd, old_addr, old_addr + extent, new_vma,
		new_pmd, new_addr, need_rmap_locks);
		}

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