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mm/mremap: calculate extent in one place

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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>
This commit is contained in:
Wei Yang 2020-08-06 23:23:44 -07:00 committed by Linus Torvalds
parent b8aa9d9d95
commit 9ad9718bfa
1 changed files with 3 additions and 3 deletions
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6
mm/mremap.c
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@ -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);
}