From 5faa0b06bad5522004d312e187ef769a12575e59 Mon Sep 17 00:00:00 2001 From: "Liam R. Howlett" Date: Sun, 5 Sep 2021 23:31:15 -0400 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. Signed-off-by: Liam R. Howlett --- mm/mmap.c | 28 ++++++++++++++++++++-------- 1 file changed, 20 insertions(+), 8 deletions(-) diff --git a/mm/mmap.c b/mm/mmap.c index f67b090e8e50..7ceed4b25e25 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -582,10 +582,11 @@ 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); @@ -613,6 +614,7 @@ 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; @@ -739,17 +741,27 @@ 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); @@ -784,7 +796,7 @@ 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) { -- 2.49.0