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
