Re: [PATCH v2] mm/hugetlb: mm/memory_hotplug: use a folio in scan_movable_pages()

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On 30.05.24 19:14, Sidhartha Kumar wrote:
By using a folio in scan_movable_pages() we convert the last user of the
page-based hugetlb information macro functions to the folio version.
After this conversion, we can safely remove the page-based definitions
from include/linux/hugetlb.h.

Signed-off-by: Sidhartha Kumar <sidhartha.kumar@xxxxxxxxxx>
---

v1 -> v2:
	simplify pfn skipping logic with pfn |= folio_nr_pages(folio) - 1
	per Matthew

  include/linux/hugetlb.h |  6 +-----
  mm/memory_hotplug.c     | 11 +++++------
  2 files changed, 6 insertions(+), 11 deletions(-)

diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 15a58f69782c..279aca379b95 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -616,9 +616,7 @@ static __always_inline						\
  bool folio_test_hugetlb_##flname(struct folio *folio)		\
  	{	void *private = &folio->private;		\
  		return test_bit(HPG_##flname, private);		\
-	}							\
-static inline int HPage##uname(struct page *page)		\
-	{ return test_bit(HPG_##flname, &(page->private)); }
+	}
#define SETHPAGEFLAG(uname, flname) \
  static __always_inline						\
@@ -637,8 +635,6 @@ void folio_clear_hugetlb_##flname(struct folio *folio)		\
  #define TESTHPAGEFLAG(uname, flname)				\
  static inline bool						\
  folio_test_hugetlb_##flname(struct folio *folio)		\
-	{ return 0; }						\
-static inline int HPage##uname(struct page *page)		\
  	{ return 0; }
#define SETHPAGEFLAG(uname, flname) \
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 431b1f6753c0..9c36eb3bbd3b 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1731,8 +1731,8 @@ static int scan_movable_pages(unsigned long start, unsigned long end,
  	unsigned long pfn;
for (pfn = start; pfn < end; pfn++) {
-		struct page *page, *head;
-		unsigned long skip;
+		struct page *page;
+		struct folio *folio;
if (!pfn_valid(pfn))
  			continue;
@@ -1753,7 +1753,7 @@ static int scan_movable_pages(unsigned long start, unsigned long end,
if (!PageHuge(page))
  			continue;
-		head = compound_head(page);
+		folio = page_folio(page);
  		/*
  		 * This test is racy as we hold no reference or lock.  The
  		 * hugetlb page could have been free'ed and head is no longer
@@ -1761,10 +1761,9 @@ static int scan_movable_pages(unsigned long start, unsigned long end,
  		 * cases false positives and negatives are possible.  Calling
  		 * code must deal with these scenarios.
  		 */
-		if (HPageMigratable(head))
+		if (folio_test_hugetlb_migratable(folio))
  			goto found;
-		skip = compound_nr(head) - (pfn - page_to_pfn(head));
-		pfn += skip - 1;
+		pfn |= folio_nr_pages(folio) - 1;

Likely not exactly what we want?

pfn |= folio_nr_pages(folio);

Would make sure that we are "one PFN before the start of the next folio". The pfn++ before the next loop iteration would move us to the next folio.

Or am I missing something?

It might be cleaner if we would handle the "pfn++;" on the "continue;" paths inmstead, and simply here do something like

	pfn = ALIGN(pfn + 1, folio_nr_pages(folio));

instead.

--
Cheers,

David / dhildenb





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