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Subject[PATCH RFC 10/10] mm/gup: Remove FOLL_LONGTERM DAX exclusion
Date
From: Ira Weiny <ira.weiny@intel.com>

Now that there is a mechanism for users to safely take LONGTERM pins on
FS DAX pages, remove the FS DAX exclusion from GUP with FOLL_LONGTERM.

Special processing remains in effect for CONFIG_CMA

Signed-off-by: Ira Weiny <ira.weiny@intel.com>
---
mm/gup.c | 78 ++++++--------------------------------------------------
1 file changed, 8 insertions(+), 70 deletions(-)

diff --git a/mm/gup.c b/mm/gup.c
index d06cc5b14c0b..4f6e5606b81e 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1392,26 +1392,6 @@ long get_user_pages_remote(struct task_struct *tsk, struct mm_struct *mm,
}
EXPORT_SYMBOL(get_user_pages_remote);

-#if defined(CONFIG_FS_DAX) || defined (CONFIG_CMA)
-static bool check_dax_vmas(struct vm_area_struct **vmas, long nr_pages)
-{
- long i;
- struct vm_area_struct *vma_prev = NULL;
-
- for (i = 0; i < nr_pages; i++) {
- struct vm_area_struct *vma = vmas[i];
-
- if (vma == vma_prev)
- continue;
-
- vma_prev = vma;
-
- if (vma_is_fsdax(vma))
- return true;
- }
- return false;
-}
-
#ifdef CONFIG_CMA
static struct page *new_non_cma_page(struct page *page, unsigned long private)
{
@@ -1542,18 +1522,6 @@ static long check_and_migrate_cma_pages(struct task_struct *tsk,

return nr_pages;
}
-#else
-static long check_and_migrate_cma_pages(struct task_struct *tsk,
- struct mm_struct *mm,
- unsigned long start,
- unsigned long nr_pages,
- struct page **pages,
- struct vm_area_struct **vmas,
- unsigned int gup_flags)
-{
- return nr_pages;
-}
-#endif

/*
* __gup_longterm_locked() is a wrapper for __get_user_pages_locked which
@@ -1567,49 +1535,28 @@ static long __gup_longterm_locked(struct task_struct *tsk,
struct vm_area_struct **vmas,
unsigned int gup_flags)
{
- struct vm_area_struct **vmas_tmp = vmas;
unsigned long flags = 0;
- long rc, i;
+ long rc;

- if (gup_flags & FOLL_LONGTERM) {
- if (!pages)
- return -EINVAL;
-
- if (!vmas_tmp) {
- vmas_tmp = kcalloc(nr_pages,
- sizeof(struct vm_area_struct *),
- GFP_KERNEL);
- if (!vmas_tmp)
- return -ENOMEM;
- }
+ if (flags & FOLL_LONGTERM)
flags = memalloc_nocma_save();
- }

rc = __get_user_pages_locked(tsk, mm, start, nr_pages, pages,
- vmas_tmp, NULL, gup_flags);
+ vmas, NULL, gup_flags);

if (gup_flags & FOLL_LONGTERM) {
memalloc_nocma_restore(flags);
if (rc < 0)
goto out;

- if (check_dax_vmas(vmas_tmp, rc)) {
- for (i = 0; i < rc; i++)
- put_page(pages[i]);
- rc = -EOPNOTSUPP;
- goto out;
- }
-
rc = check_and_migrate_cma_pages(tsk, mm, start, rc, pages,
- vmas_tmp, gup_flags);
+ vmas, gup_flags);
}

out:
- if (vmas_tmp != vmas)
- kfree(vmas_tmp);
return rc;
}
-#else /* !CONFIG_FS_DAX && !CONFIG_CMA */
+#else /* !CONFIG_CMA */
static __always_inline long __gup_longterm_locked(struct task_struct *tsk,
struct mm_struct *mm,
unsigned long start,
@@ -1621,7 +1568,7 @@ static __always_inline long __gup_longterm_locked(struct task_struct *tsk,
return __get_user_pages_locked(tsk, mm, start, nr_pages, pages, vmas,
NULL, flags);
}
-#endif /* CONFIG_FS_DAX || CONFIG_CMA */
+#endif /* CONFIG_CMA */

/*
* This is the same as get_user_pages_remote(), just with a
@@ -1882,9 +1829,6 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
goto pte_unmap;

if (pte_devmap(pte)) {
- if (unlikely(flags & FOLL_LONGTERM))
- goto pte_unmap;
-
pgmap = get_dev_pagemap(pte_pfn(pte), pgmap);
if (unlikely(!pgmap)) {
undo_dev_pagemap(nr, nr_start, pages);
@@ -2057,12 +2001,9 @@ static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
if (!pmd_access_permitted(orig, flags & FOLL_WRITE))
return 0;

- if (pmd_devmap(orig)) {
- if (unlikely(flags & FOLL_LONGTERM))
- return 0;
+ if (pmd_devmap(orig))
return __gup_device_huge_pmd(orig, pmdp, addr, end, pages, nr,
flags);
- }

refs = 0;
page = pmd_page(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
@@ -2101,12 +2042,9 @@ static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
if (!pud_access_permitted(orig, flags & FOLL_WRITE))
return 0;

- if (pud_devmap(orig)) {
- if (unlikely(flags & FOLL_LONGTERM))
- return 0;
+ if (pud_devmap(orig))
return __gup_device_huge_pud(orig, pudp, addr, end, pages, nr,
flags);
- }

refs = 0;
page = pud_page(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
--
2.20.1
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