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mmap: change zeroing of maple tree in __vma_adjust()

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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/20220906194824.2110408-19-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Tested-by: Yu Zhao <yuzhao@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: SeongJae Park <sj@kernel.org>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Liam R. Howlett 2022-09-06 19:48:49 +00:00 committed by Andrew Morton
parent 524e00b36e
commit 3b0e81a1cd
1 changed files with 22 additions and 8 deletions
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30
mm/mmap.c
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@ -567,11 +567,11 @@ static int vma_link(struct mm_struct *mm, struct vm_area_struct *vma,
* 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 ma_state *mas,
struct vm_area_struct *vma)
struct vm_area_struct *vma, unsigned long location)
{
struct vm_area_struct *prev;
mas_set(mas, vma->vm_start);
mas_set(mas, location);
prev = mas_prev(mas, 0);
vma_mas_store(vma, mas);
__vma_link_list(mm, vma, prev);
@ -601,6 +601,7 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start,
int remove_next = 0;
MA_STATE(mas, &mm->mm_mt, 0, 0);
struct vm_area_struct *exporter = NULL, *importer = NULL;
unsigned long ll_prev = vma->vm_start; /* linked list prev. */
if (next && !insert) {
if (end >= next->vm_end) {
@ -728,15 +729,27 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start,
}
if (start != vma->vm_start) {
if (vma->vm_start < start)
if ((vma->vm_start < start) &&
(!insert || (insert->vm_end != start))) {
vma_mas_szero(&mas, vma->vm_start, start);
vma_changed = true;
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_mas_szero(&mas, end, vma->vm_end);
vma_changed = true;
if (vma->vm_end > end) {
if (!insert || (insert->vm_start != end)) {
vma_mas_szero(&mas, 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);
@ -783,7 +796,7 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start,
* us to insert it before dropping the locks
* (it may either follow vma or precede it).
*/
__insert_vm_struct(mm, &mas, insert);
__insert_vm_struct(mm, &mas, insert, ll_prev);
}
if (anon_vma) {
@ -870,6 +883,7 @@ again:
if (insert && file)
uprobe_mmap(insert);
mas_destroy(&mas);
validate_mm(mm);
return 0;
}