From 0da860625a5d3091914cca969646bbf9f4462ffb 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. Signed-off-by: Liam R. Howlett --- mm/mmap.c | 21 +++++++++++++-------- 1 file changed, 13 insertions(+), 8 deletions(-) diff --git a/mm/mmap.c b/mm/mmap.c index 992ba12a72d4..f11492767b40 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -627,6 +627,7 @@ 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 old_start; if (next && !insert) { struct vm_area_struct *exporter = NULL, *importer = NULL; @@ -752,25 +753,29 @@ again: vma_interval_tree_remove(next, root); } + old_start = vma->vm_start; if (start != vma->vm_start) { - if (vma->vm_start < start) - vma_mt_szero(mm, vma->vm_start, start); - else - vma_changed = true; + 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 && (insert->vm_start != end))) + vma_mt_szero(mm, end, vma->vm_end); + } else vma_changed = true; vma->vm_end = end; if (!next) mm->highest_vm_end = vm_end_gap(vma); } - if (vma_changed) + if (vma_changed) { vma_mt_store(mm, vma); + if (old_start < start) { + if (insert && (insert->vm_start != old_start)) + vma_mt_szero(mm, old_start, start); + } + } vma->vm_pgoff = pgoff; if (adjust_next) { -- 2.50.1