On 3/22/21 7:15 AM, Michal Hocko wrote:

On Fri 19-03-21 15:42:04, Mike Kravetz wrote:

quoted

The new remove_hugetlb_page() routine is designed to remove a hugetlb
page from hugetlbfs processing.  It will remove the page from the active
or free list, update global counters and set the compound page
destructor to NULL so that PageHuge() will return false for the 'page'.
After this call, the 'page' can be treated as a normal compound page or
a collection of base size pages.

remove_hugetlb_page is to be called with the hugetlb_lock held.

Creating this routine and separating functionality is in preparation for
restructuring code to reduce lock hold times.

I like this! Counters handling both in __free_huge_page and
update_and_free_page is really confusing.

quoted

Signed-off-by: Mike Kravetz <redacted>
---
 mm/hugetlb.c | 70 ++++++++++++++++++++++++++++++++++------------------
 1 file changed, 46 insertions(+), 24 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index c537274c2a38..ae185d3315e0 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c

@@ -1306,6 +1306,46 @@ static inline void destroy_compound_gigantic_page(struct page *page,
 						unsigned int order) { }
 #endif
 
+/*
+ * Remove hugetlb page from lists, and update dtor so that page appears
+ * as just a compound page.  A reference is held on the page.
+ * NOTE: hugetlb specific page flags stored in page->private are not
+ *	 automatically cleared.  These flags may be used in routines
+ *	 which operate on the resulting compound page.
+ *
+ * Must be called with hugetlb lock held.
+ */
+static void remove_hugetlb_page(struct hstate *h, struct page *page,
+							bool adjust_surplus)
+{
+	int nid = page_to_nid(page);
+

I think we want lockdep_assert_held here. Lockdep asserts are not used
in this code but now that you are touching it then it is probably better
to start adding them. What do you think?

Yes, with this type of change we add lockdep tests/qualifiers.  They are
lacking in the code, and would be helpful.

I will add them.
-- 
Mike Kravetz