From b1357c01ba2e71f3bb645a1dbd51a818f5f702ab Mon Sep 17 00:00:00 2001 From: Liam Howlett Date: Wed, 13 Apr 2022 23:07:15 -0700 Subject: [PATCH] mmap: change zeroing of maple tree in __vma_adjust() Only write to the maple tree if we are not inserting or the insert isn't going to overwrite the area to clear. This avoids spanning writes and node coealescing when unnecessary. The change requires a custom search for the linked list addition to find the correct VMA for the prev link. Link: https://lkml.kernel.org/r/20220404143501.2016403-21-Liam.Howlett@oracle.com Signed-off-by: Liam R. Howlett Signed-off-by: Andrew Morton --- mm/mmap.c | 28 ++++++++++++++++++++-------- 1 file changed, 20 insertions(+), 8 deletions(-) diff --git a/mm/mmap.c b/mm/mmap.c index 58ff4bdf1adf..8b923160cd8a 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -590,10 +590,11 @@ static void vma_link(struct mm_struct *mm, struct vm_area_struct *vma, * Helper for vma_adjust() in the split_vma insert case: insert a vma into the * mm's list and the mm tree. It has already been inserted into the interval tree. */ -static void __insert_vm_struct(struct mm_struct *mm, struct vm_area_struct *vma) +static void __insert_vm_struct(struct mm_struct *mm, struct vm_area_struct *vma, + unsigned long location) { struct vm_area_struct *prev; - MA_STATE(mas, &mm->mm_mt, vma->vm_start, vma->vm_start); + MA_STATE(mas, &mm->mm_mt, location, location); prev = mas_prev(&mas, 0); vma_store(mm, vma); @@ -621,6 +622,7 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start, bool vma_changed = false; long adjust_next = 0; int remove_next = 0; + unsigned long ll_prev = vma->vm_start; /* linked list prev. */ if (next && !insert) { struct vm_area_struct *exporter = NULL, *importer = NULL; @@ -747,17 +749,27 @@ again: } if (start != vma->vm_start) { - if (vma->vm_start < start) + if ((vma->vm_start < start) && + (!insert || (insert->vm_end != start))) { vma_mt_szero(mm, vma->vm_start, start); - else + VM_WARN_ON(insert && insert->vm_start > vma->vm_start); + } else { vma_changed = true; + } vma->vm_start = start; } if (end != vma->vm_end) { - if (vma->vm_end > end) - vma_mt_szero(mm, end, vma->vm_end); - else + if (vma->vm_end > end) { + if (!insert || (insert->vm_start != end)) { + vma_mt_szero(mm, end, vma->vm_end); + VM_WARN_ON(insert && + insert->vm_end < vma->vm_end); + } else if (insert->vm_start == end) { + ll_prev = vma->vm_end; + } + } else { vma_changed = true; + } vma->vm_end = end; if (!next) mm->highest_vm_end = vm_end_gap(vma); @@ -792,7 +804,7 @@ again: * us to insert it before dropping the locks * (it may either follow vma or precede it). */ - __insert_vm_struct(mm, insert); + __insert_vm_struct(mm, insert, ll_prev); } if (anon_vma) { -- 2.50.1