+ mm-gup-add-foll_longterm-capability-to-gup-fast.patch added to -mm tree

[akpm@xxxxxxxxxxxxxxxxxxxx]

The patch titled
     Subject: mm/gup: add FOLL_LONGTERM capability to GUP fast
has been added to the -mm tree.  Its filename is
     mm-gup-add-foll_longterm-capability-to-gup-fast.patch

This patch should soon appear at
    http://ozlabs.org/~akpm/mmots/broken-out/mm-gup-add-foll_longterm-capability-to-gup-fast.patch
and later at
    http://ozlabs.org/~akpm/mmotm/broken-out/mm-gup-add-foll_longterm-capability-to-gup-fast.patch

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------------------------------------------------------
From: Ira Weiny <ira.weiny@xxxxxxxxx>
Subject: mm/gup: add FOLL_LONGTERM capability to GUP fast

DAX pages were previously unprotected from longterm pins when users called
get_user_pages_fast().

Use the new FOLL_LONGTERM flag to check for DEVMAP pages and fall back to
regular GUP processing if a DEVMAP page is encountered.

Link: http://lkml.kernel.org/r/20190317183438.2057-5-ira.weiny@xxxxxxxxx
Signed-off-by: Ira Weiny <ira.weiny@xxxxxxxxx>
Cc: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>
Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
Cc: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: James Hogan <jhogan@xxxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxx>
Cc: John Hubbard <jhubbard@xxxxxxxxxx>
Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
Cc: Rich Felker <dalias@xxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Yoshinori Sato <ysato@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 mm/gup.c |   29 +++++++++++++++++++++++++----
 1 file changed, 25 insertions(+), 4 deletions(-)

--- a/mm/gup.c~mm-gup-add-foll_longterm-capability-to-gup-fast
+++ a/mm/gup.c
@@ -1600,6 +1600,9 @@ static int gup_pte_range(pmd_t pmd, unsi
 			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);
@@ -1739,8 +1742,11 @@ static int gup_huge_pmd(pmd_t orig, pmd_
 	if (!pmd_access_permitted(orig, flags & FOLL_WRITE))
 		return 0;
 
-	if (pmd_devmap(orig))
+	if (pmd_devmap(orig)) {
+		if (unlikely(flags & FOLL_LONGTERM))
+			return 0;
 		return __gup_device_huge_pmd(orig, pmdp, addr, end, pages, nr);
+	}
 
 	refs = 0;
 	page = pmd_page(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
@@ -1777,8 +1783,11 @@ static int gup_huge_pud(pud_t orig, pud_
 	if (!pud_access_permitted(orig, flags & FOLL_WRITE))
 		return 0;
 
-	if (pud_devmap(orig))
+	if (pud_devmap(orig)) {
+		if (unlikely(flags & FOLL_LONGTERM))
+			return 0;
 		return __gup_device_huge_pud(orig, pudp, addr, end, pages, nr);
+	}
 
 	refs = 0;
 	page = pud_page(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
@@ -2066,8 +2075,20 @@ int get_user_pages_fast(unsigned long st
 		start += nr << PAGE_SHIFT;
 		pages += nr;
 
-		ret = get_user_pages_unlocked(start, nr_pages - nr, pages,
-					      gup_flags);
+		if (gup_flags & FOLL_LONGTERM) {
+			down_read(&current->mm->mmap_sem);
+			ret = __gup_longterm_locked(current, current->mm,
+						    start, nr_pages - nr,
+						    pages, NULL, gup_flags);
+			up_read(&current->mm->mmap_sem);
+		} else {
+			/*
+			 * retain FAULT_FOLL_ALLOW_RETRY optimization if
+			 * possible
+			 */
+			ret = get_user_pages_unlocked(start, nr_pages - nr,
+						      pages, gup_flags);
+		}
 
 		/* Have to be a bit careful with return values */
 		if (nr > 0) {
_

Patches currently in -mm which might be from ira.weiny@xxxxxxxxx are

mm-gup-replace-get_user_pages_longterm-with-foll_longterm.patch
mm-gup-change-write-parameter-to-flags-in-fast-walk.patch
mm-gup-change-gup-fast-to-use-flags-rather-than-a-write-bool.patch
mm-gup-add-foll_longterm-capability-to-gup-fast.patch
ib-hfi1-use-the-new-foll_longterm-flag-to-get_user_pages_fast.patch
ib-qib-use-the-new-foll_longterm-flag-to-get_user_pages_fast.patch
ib-mthca-use-the-new-foll_longterm-flag-to-get_user_pages_fast.patch