Re: [PATCH v3 07/12] mm/gup: track FOLL_PIN pages
From: Kirill A. Shutemov <hidden>
Date: 2020-02-03 13:40:17
Also in:
linux-fsdevel, linux-kselftest, linux-mm, linux-rdma, lkml
On Fri, Jan 31, 2020 at 07:40:24PM -0800, John Hubbard wrote:
quoted hunk ↗ jump to hunk
@@ -4405,7 +4392,13 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma, same_page: if (pages) { pages[i] = mem_map_offset(page, pfn_offset); - get_page(pages[i]); + if (!try_grab_page(pages[i], flags)) { + spin_unlock(ptl); + remainder = 0; + err = -ENOMEM; + WARN_ON_ONCE(1);
The WARN_ON_ONCE deserve a comment. And I guess you can put it into 'if' condition.
quoted hunk ↗ jump to hunk
+ break; + } } if (vmas)@@ -4965,6 +4958,12 @@ follow_huge_pmd(struct mm_struct *mm, unsigned long address, struct page *page = NULL; spinlock_t *ptl; pte_t pte; + + /* FOLL_GET and FOLL_PIN are mutually exclusive. */ + if (WARN_ON_ONCE((flags & (FOLL_PIN | FOLL_GET)) == + (FOLL_PIN | FOLL_GET))) + return NULL; + retry: ptl = pmd_lockptr(mm, pmd); spin_lock(ptl);@@ -4977,8 +4976,11 @@ follow_huge_pmd(struct mm_struct *mm, unsigned long address, pte = huge_ptep_get((pte_t *)pmd); if (pte_present(pte)) { page = pmd_page(*pmd) + ((address & ~PMD_MASK) >> PAGE_SHIFT); - if (flags & FOLL_GET) - get_page(page); + if (unlikely(!try_grab_page(page, flags))) { + WARN_ON_ONCE(1);
Ditto.
+ page = NULL;
+ goto out;
+ }
} else {
if (is_hugetlb_entry_migration(pte)) {
spin_unlock(ptl);-- Kirill A. Shutemov