[merged mm-stable] mm-gup-fix-comments-to-pin_user_pages_.patch removed from -mm tree

[Andrew Morton <akpm@linux-foundation.org>]

The quilt patch titled
     Subject: mm/gup: fix comments to pin_user_pages_*()
has been removed from the -mm tree.  Its filename was
     mm-gup-fix-comments-to-pin_user_pages_.patch

This patch was dropped because it was merged into mm-stable

------------------------------------------------------
From: Yury Norov <yury.norov@gmail.com>
Subject: mm/gup: fix comments to pin_user_pages_*()

pin_user_pages API forces FOLL_PIN in gup_flags, which means that the API
requires struct page **pages to be provided (not NULL).  However, the
comment to pin_user_pages() clearly allows for passing in a NULL @pages
argument.

Remove the incorrect comments, and add WARN_ON_ONCE(!pages) calls to
enforce the API.

It has been independently spotted by Minchan Kim and confirmed with
John Hubbard:

https://lore.kernel.org/all/YgWA0ghrrzHONehH@google.com/

Link: https://lkml.kernel.org/r/20220422015839.1274328-1-yury.norov@gmail.com
Signed-off-by: Yury Norov (NVIDIA) <yury.norov@gmail.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/gup.c |   21 +++++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

--- a/mm/gup.c~mm-gup-fix-comments-to-pin_user_pages_
+++ a/mm/gup.c
@@ -2969,6 +2969,9 @@ int pin_user_pages_fast(unsigned long st
 	if (WARN_ON_ONCE(gup_flags & FOLL_GET))
 		return -EINVAL;
 
+	if (WARN_ON_ONCE(!pages))
+		return -EINVAL;
+
 	gup_flags |= FOLL_PIN;
 	return internal_get_user_pages_fast(start, nr_pages, gup_flags, pages);
 }
@@ -2991,6 +2994,9 @@ int pin_user_pages_fast_only(unsigned lo
 	 */
 	if (WARN_ON_ONCE(gup_flags & FOLL_GET))
 		return 0;
+
+	if (WARN_ON_ONCE(!pages))
+		return 0;
 	/*
 	 * FOLL_FAST_ONLY is required in order to match the API description of
 	 * this routine: no fall back to regular ("slow") GUP.
@@ -3018,8 +3024,7 @@ EXPORT_SYMBOL_GPL(pin_user_pages_fast_on
  * @nr_pages:	number of pages from start to pin
  * @gup_flags:	flags modifying lookup behaviour
  * @pages:	array that receives pointers to the pages pinned.
- *		Should be at least nr_pages long. Or NULL, if caller
- *		only intends to ensure the pages are faulted in.
+ *		Should be at least nr_pages long.
  * @vmas:	array of pointers to vmas corresponding to each page.
  *		Or NULL if the caller does not require them.
  * @locked:	pointer to lock flag indicating whether lock is held and
@@ -3042,6 +3047,9 @@ long pin_user_pages_remote(struct mm_str
 	if (WARN_ON_ONCE(gup_flags & FOLL_GET))
 		return -EINVAL;
 
+	if (WARN_ON_ONCE(!pages))
+		return -EINVAL;
+
 	gup_flags |= FOLL_PIN;
 	return __get_user_pages_remote(mm, start, nr_pages, gup_flags,
 				       pages, vmas, locked);
@@ -3055,8 +3063,7 @@ EXPORT_SYMBOL(pin_user_pages_remote);
  * @nr_pages:	number of pages from start to pin
  * @gup_flags:	flags modifying lookup behaviour
  * @pages:	array that receives pointers to the pages pinned.
- *		Should be at least nr_pages long. Or NULL, if caller
- *		only intends to ensure the pages are faulted in.
+ *		Should be at least nr_pages long.
  * @vmas:	array of pointers to vmas corresponding to each page.
  *		Or NULL if the caller does not require them.
  *
@@ -3074,6 +3081,9 @@ long pin_user_pages(unsigned long start,
 	if (WARN_ON_ONCE(gup_flags & FOLL_GET))
 		return -EINVAL;
 
+	if (WARN_ON_ONCE(!pages))
+		return -EINVAL;
+
 	gup_flags |= FOLL_PIN;
 	return __gup_longterm_locked(current->mm, start, nr_pages,
 				     pages, vmas, gup_flags);
@@ -3092,6 +3102,9 @@ long pin_user_pages_unlocked(unsigned lo
 	if (WARN_ON_ONCE(gup_flags & FOLL_GET))
 		return -EINVAL;
 
+	if (WARN_ON_ONCE(!pages))
+		return -EINVAL;
+
 	gup_flags |= FOLL_PIN;
 	return get_user_pages_unlocked(start, nr_pages, pages, gup_flags);
 }
_

Patches currently in -mm which might be from yury.norov@gmail.com are