Re: [PATCH v2 1/5] mm: memory_hotplug: remove head variable in do_migrate_range()

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 





On 2024/8/19 17:28, Jonathan Cameron wrote:
On Sat, 17 Aug 2024 16:49:37 +0800
Kefeng Wang <wangkefeng.wang@xxxxxxxxxx> wrote:

Directly use a folio for HugeTLB and THP when calculate the next pfn,
then remove unused head variable.

Signed-off-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>

Hi,

I was curious so had a read and have a quick comment
on the comment.


---
  mm/memory_hotplug.c | 22 ++++++++++++++--------
  1 file changed, 14 insertions(+), 8 deletions(-)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index df291f2e509d..dc19b0e28fbc 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1773,7 +1773,7 @@ static int scan_movable_pages(unsigned long start, unsigned long end,
  static void do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
  {
  	unsigned long pfn;
-	struct page *page, *head;
+	struct page *page;
  	LIST_HEAD(source);
  	static DEFINE_RATELIMIT_STATE(migrate_rs, DEFAULT_RATELIMIT_INTERVAL,
  				      DEFAULT_RATELIMIT_BURST);
@@ -1786,14 +1786,20 @@ static void do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
  			continue;
  		page = pfn_to_page(pfn);
  		folio = page_folio(page);
-		head = &folio->page;
- if (PageHuge(page)) {
-			pfn = page_to_pfn(head) + compound_nr(head) - 1;
-			isolate_hugetlb(folio, &source);
-			continue;
-		} else if (PageTransHuge(page))
-			pfn = page_to_pfn(head) + thp_nr_pages(page) - 1;
+		/*
+		 * The folio hold no reference or lock, it might be changed
+		 * concurrently(eg, split), folio_nr_pages() may read garbage,
+		 * but out loop could handle that as it revisits the split
+		 * folio later.
+		 */
Perhaps reword this (it confused me a bit) I'm not sure I've retained
the intended meaning!

		* No reference or lock is held on the folio, so it might
		* be modified concurrently (e.g. split).  As such,
		* folio_nr_pages() may read garbage.  This is fine as the
		* outer loop will revisit the split folio later.

Thanks. hope Andrew could squash it if no more comments about this
patchset, or I will resend a new version with comment changes.




+		if (folio_test_large(folio)) {
+			pfn = folio_pfn(folio) + folio_nr_pages(folio) - 1;
+			if (folio_test_hugetlb(folio)) {
+				isolate_hugetlb(folio, &source);
+				continue;
+			}
+		}
/*
  		 * HWPoison pages have elevated reference counts so the migration would





[Index of Archives]     [Linux ARM Kernel]     [Linux ARM]     [Linux Omap]     [Fedora ARM]     [IETF Annouce]     [Bugtraq]     [Linux OMAP]     [Linux MIPS]     [eCos]     [Asterisk Internet PBX]     [Linux API]

  Powered by Linux