+ userfaultfd-selftests-clean-up-hugetlb-allocation-code.patch added to -mm tree

[akpm@linux-foundation.org]

The patch titled
     Subject: userfaultfd/selftests: clean up hugetlb allocation code
has been added to the -mm tree.  Its filename is
     userfaultfd-selftests-clean-up-hugetlb-allocation-code.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/userfaultfd-selftests-clean-up-hugetlb-allocation-code.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/userfaultfd-selftests-clean-up-hugetlb-allocation-code.patch

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------------------------------------------------------
From: Mike Kravetz <mike.kravetz@oracle.com>
Subject: userfaultfd/selftests: clean up hugetlb allocation code

The message for commit f5c73297181c ("userfaultfd/selftests: fix hugetlb
area allocations") says there is no need to create a hugetlb file in the
non-shared testing case.  However, the commit did not actually change the
code to prevent creation of the file.

While it is technically true that there is no need to create and use a
hugetlb file in the case of non-shared-testing, it is useful.  This is
because 'hole punching' of a hugetlb file has the potentially incorrect
side effect of also removing pages from private mappings.  The userfaultfd
test relies on this side effect for removing pages from the destination
buffer during rounds of stress testing.

Remove the incomplete code that was added to deal with no hugetlb file. 
Just keep the code that prevents reserves from being created for the
destination area.

Link: https://lkml.kernel.org/r/20220104021729.111006-1-mike.kravetz@oracle.com
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Axel Rasmussen <axelrasmussen@google.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 tools/testing/selftests/vm/userfaultfd.c |   15 ++++++---------
 1 file changed, 6 insertions(+), 9 deletions(-)

--- a/tools/testing/selftests/vm/userfaultfd.c~userfaultfd-selftests-clean-up-hugetlb-allocation-code
+++ a/tools/testing/selftests/vm/userfaultfd.c
@@ -87,7 +87,7 @@ static bool test_uffdio_minor = false;
 
 static bool map_shared;
 static int shm_fd;
-static int huge_fd = -1;	/* only used for hugetlb_shared test */
+static int huge_fd;
 static char *huge_fd_off0;
 static unsigned long long *count_verify;
 static int uffd = -1;
@@ -223,9 +223,6 @@ static void noop_alias_mapping(__u64 *st
 
 static void hugetlb_release_pages(char *rel_area)
 {
-	if (huge_fd == -1)
-		return;
-
 	if (fallocate(huge_fd, FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE,
 		      rel_area == huge_fd_off0 ? 0 : nr_pages * page_size,
 		      nr_pages * page_size))
@@ -238,17 +235,17 @@ static void hugetlb_allocate_area(void *
 	char **alloc_area_alias;
 
 	*alloc_area = mmap(NULL, nr_pages * page_size, PROT_READ | PROT_WRITE,
-			   map_shared ? MAP_SHARED :
-			   MAP_PRIVATE | MAP_HUGETLB |
+			   (map_shared ? MAP_SHARED : MAP_PRIVATE) |
+			   MAP_HUGETLB |
 			   (*alloc_area == area_src ? 0 : MAP_NORESERVE),
-			   huge_fd,
-			   *alloc_area == area_src ? 0 : nr_pages * page_size);
+			   huge_fd, *alloc_area == area_src ? 0 :
+			   nr_pages * page_size);
 	if (*alloc_area == MAP_FAILED)
 		err("mmap of hugetlbfs file failed");
 
 	if (map_shared) {
 		area_alias = mmap(NULL, nr_pages * page_size, PROT_READ | PROT_WRITE,
-				  MAP_SHARED,
+				  MAP_SHARED | MAP_HUGETLB,
 				  huge_fd, *alloc_area == area_src ? 0 :
 				  nr_pages * page_size);
 		if (area_alias == MAP_FAILED)
_

Patches currently in -mm which might be from mike.kravetz@oracle.com are

userfaultfd-selftests-clean-up-hugetlb-allocation-code.patch