On Tue, Mar 28, 2023 at 01:14:34PM +1100, Alistair Popple wrote:
+++ b/mm/memory.c @@ -3623,8 +3623,19 @@ static vm_fault_t remove_device_exclusive_entry(struct vm_fault *vmf) struct vm_area_struct *vma = vmf->vma; struct mmu_notifier_range range;
- if (!folio_lock_or_retry(folio, vma->vm_mm, vmf->flags))
- /*
* We need a page reference to lock the page because we don't* hold the PTL so a racing thread can remove the* device-exclusive entry and unmap the page. If the page is* free the entry must have been removed already.*/- if (!get_page_unless_zero(vmf->page))
return 0;
From a folio point of view: what the hell are you doing here? Tail pages don't have individual refcounts; all the refcounts are actually taken on the folio. So this should be:
if (!folio_try_get(folio)) return 0;
(you can fix up the comment yourself)
- if (!folio_lock_or_retry(folio, vma->vm_mm, vmf->flags)) {
put_page(vmf->page);
folio_put(folio);
return VM_FAULT_RETRY;
- } mmu_notifier_range_init_owner(&range, MMU_NOTIFY_EXCLUSIVE, 0, vma, vma->vm_mm, vmf->address & PAGE_MASK, (vmf->address & PAGE_MASK) + PAGE_SIZE, NULL);
@@ -3637,6 +3648,7 @@ static vm_fault_t remove_device_exclusive_entry(struct vm_fault *vmf) pte_unmap_unlock(vmf->pte, vmf->ptl); folio_unlock(folio);
- put_page(vmf->page);
folio_put(folio)
There, I just saved you 3 calls to compound_head(), saving roughly 150 bytes of kernel text.
mmu_notifier_invalidate_range_end(&range); return 0; -- 2.39.2