No need for a special flag that is not even properly documented to be
internal-only.
Let's just factor this check out and get rid of this flag. The separate
function has the nice benefit that we can centralize comments.
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
---
include/linux/mm.h | 16 +++++++++++++++-
mm/gup.c | 12 ++----------
mm/huge_memory.c | 2 +-
3 files changed, 18 insertions(+), 12 deletions(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 982f2607180b..8b85765d7a98 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2881,7 +2881,6 @@ struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
* and return without waiting upon it */
#define FOLL_NOFAULT 0x80 /* do not fault in pages */
#define FOLL_HWPOISON 0x100 /* check page is hwpoisoned */
-#define FOLL_NUMA 0x200 /* force NUMA hinting page fault */
#define FOLL_MIGRATION 0x400 /* wait for page to replace migration entry */
#define FOLL_TRIED 0x800 /* a retry, previous pass started an IO */
#define FOLL_REMOTE 0x2000 /* we are working on non-current tsk/mm */
@@ -2997,6 +2996,21 @@ static inline bool gup_must_unshare(unsigned int flags, struct page *page)
return !PageAnonExclusive(page);
}
+/*
+ * Indicates whether GUP can follow a PROT_NONE mapped page, or whether
+ * a (NUMA hinting) fault is required.
+ */
+static inline bool gup_can_follow_protnone(unsigned int flags)
+{
+ /*
+ * FOLL_FORCE has to be able to make progress even if the VMA is
+ * inaccessible. Further, FOLL_FORCE access usually does not represent
+ * application behaviour and we should avoid triggering NUMA hinting
+ * faults.
+ */
+ return flags & FOLL_FORCE;
+}
+
typedef int (*pte_fn_t)(pte_t *pte, unsigned long addr, void *data);
extern int apply_to_page_range(struct mm_struct *mm, unsigned long address,
unsigned long size, pte_fn_t fn, void *data);
diff --git a/mm/gup.c b/mm/gup.c
index 5abdaf487460..a1355dbd848e 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -554,7 +554,7 @@ static struct page *follow_page_pte(struct vm_area_struct *vma,
migration_entry_wait(mm, pmd, address);
goto retry;
}
- if ((flags & FOLL_NUMA) && pte_protnone(pte))
+ if (pte_protnone(pte) && !gup_can_follow_protnone(flags))
goto no_page;
page = vm_normal_page(vma, address, pte);
@@ -707,7 +707,7 @@ static struct page *follow_pmd_mask(struct vm_area_struct *vma,
if (likely(!pmd_trans_huge(pmdval)))
return follow_page_pte(vma, address, pmd, flags, &ctx->pgmap);
- if ((flags & FOLL_NUMA) && pmd_protnone(pmdval))
+ if (pmd_protnone(pmdval) && !gup_can_follow_protnone(flags))
return no_page_table(vma, flags);
retry_locked:
@@ -1153,14 +1153,6 @@ static long __get_user_pages(struct mm_struct *mm,
VM_BUG_ON(!!pages != !!(gup_flags & (FOLL_GET | FOLL_PIN)));
- /*
- * If FOLL_FORCE is set then do not force a full fault as the hinting
- * fault information is unrelated to the reference behaviour of a task
- * using the address space
- */
- if (!(gup_flags & FOLL_FORCE))
- gup_flags |= FOLL_NUMA;
-
do {
struct page *page;
unsigned int foll_flags = gup_flags;
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index e9414ee57c5b..482c1826e723 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1449,7 +1449,7 @@ struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
return ERR_PTR(-EFAULT);
/* Full NUMA hinting faults to serialise migration in fault paths */
- if ((flags & FOLL_NUMA) && pmd_protnone(*pmd))
+ if (pmd_protnone(*pmd) && !gup_can_follow_protnone(flags))
return NULL;
if (!pmd_write(*pmd) && gup_must_unshare(flags, page))
--
2.37.1
