From: Jason Gunthorpe jgg@mellanox.com
The checking boils down to some racy check if the pagemap is still available or not. Instead of checking this, rely entirely on the notifiers, if a pagemap is destroyed then all pages that belong to it must be removed from the tables and the notifiers triggered.
Signed-off-by: Jason Gunthorpe jgg@mellanox.com --- mm/hmm.c | 50 ++------------------------------------------------ 1 file changed, 2 insertions(+), 48 deletions(-)
diff --git a/mm/hmm.c b/mm/hmm.c index a491d9aaafe45d..3a2610e0713329 100644 --- a/mm/hmm.c +++ b/mm/hmm.c @@ -28,7 +28,6 @@
struct hmm_vma_walk { struct hmm_range *range; - struct dev_pagemap *pgmap; unsigned long last; unsigned int flags; }; @@ -196,19 +195,8 @@ static int hmm_vma_handle_pmd(struct mm_walk *walk, unsigned long addr, return hmm_vma_fault(addr, end, fault, write_fault, walk);
pfn = pmd_pfn(pmd) + ((addr & ~PMD_MASK) >> PAGE_SHIFT); - for (i = 0; addr < end; addr += PAGE_SIZE, i++, pfn++) { - if (pmd_devmap(pmd)) { - hmm_vma_walk->pgmap = get_dev_pagemap(pfn, - hmm_vma_walk->pgmap); - if (unlikely(!hmm_vma_walk->pgmap)) - return -EBUSY; - } + for (i = 0; addr < end; addr += PAGE_SIZE, i++, pfn++) pfns[i] = hmm_device_entry_from_pfn(range, pfn) | cpu_flags; - } - if (hmm_vma_walk->pgmap) { - put_dev_pagemap(hmm_vma_walk->pgmap); - hmm_vma_walk->pgmap = NULL; - } hmm_vma_walk->last = end; return 0; } @@ -300,15 +288,6 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr, if (fault || write_fault) goto fault;
- if (pte_devmap(pte)) { - hmm_vma_walk->pgmap = get_dev_pagemap(pte_pfn(pte), - hmm_vma_walk->pgmap); - if (unlikely(!hmm_vma_walk->pgmap)) { - pte_unmap(ptep); - return -EBUSY; - } - } - /* * Since each architecture defines a struct page for the zero page, just * fall through and treat it like a normal page. @@ -328,10 +307,6 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr, return 0;
fault: - if (hmm_vma_walk->pgmap) { - put_dev_pagemap(hmm_vma_walk->pgmap); - hmm_vma_walk->pgmap = NULL; - } pte_unmap(ptep); /* Fault any virtual address we were asked to fault */ return hmm_vma_fault(addr, end, fault, write_fault, walk); @@ -418,16 +393,6 @@ static int hmm_vma_walk_pmd(pmd_t *pmdp, return r; } } - if (hmm_vma_walk->pgmap) { - /* - * We do put_dev_pagemap() here and not in hmm_vma_handle_pte() - * so that we can leverage get_dev_pagemap() optimization which - * will not re-take a reference on a pgmap if we already have - * one. - */ - put_dev_pagemap(hmm_vma_walk->pgmap); - hmm_vma_walk->pgmap = NULL; - } pte_unmap(ptep - 1);
hmm_vma_walk->last = addr; @@ -491,20 +456,9 @@ static int hmm_vma_walk_pud(pud_t *pudp, unsigned long start, unsigned long end, }
pfn = pud_pfn(pud) + ((addr & ~PUD_MASK) >> PAGE_SHIFT); - for (i = 0; i < npages; ++i, ++pfn) { - hmm_vma_walk->pgmap = get_dev_pagemap(pfn, - hmm_vma_walk->pgmap); - if (unlikely(!hmm_vma_walk->pgmap)) { - ret = -EBUSY; - goto out_unlock; - } + for (i = 0; i < npages; ++i, ++pfn) pfns[i] = hmm_device_entry_from_pfn(range, pfn) | cpu_flags; - } - if (hmm_vma_walk->pgmap) { - put_dev_pagemap(hmm_vma_walk->pgmap); - hmm_vma_walk->pgmap = NULL; - } hmm_vma_walk->last = end; goto out_unlock; }