在 2025/5/22 13:34, Oscar Salvador 写道:
On Thu, May 22, 2025 at 11:47:05AM +0800, Muchun Song wrote:
Thanks for fixing this problem. BTW, in order to catch future similar problem, it is better to add WARN_ON into folio_hstate() to assert if hugetlb_lock is not held when folio's reference count is zero. For this fix, LGTM.
Why cannot we put all the burden in alloc_and_dissolve_hugetlb_folio(), which will again check things under the lock? I mean, I would be ok to save cycles and check upfront in replace_free_hugepage_folios(), but the latter has only one user which is alloc_contig_range(), which is not really an expected-to-be optimized function.
diff --git a/mm/hugetlb.c b/mm/hugetlb.c index bd8971388236..b4d937732256 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -2924,13 +2924,6 @@ int replace_free_hugepage_folios(unsigned long start_pfn, unsigned long end_pfn) while (start_pfn < end_pfn) { folio = pfn_folio(start_pfn);
if (folio_test_hugetlb(folio)) {h = folio_hstate(folio);} else {start_pfn++;continue;}if (!folio_ref_count(folio)) { ret = alloc_and_dissolve_hugetlb_folio(h, folio, &isolate_list);
It seems that we cannot simply remove the folio_test_hugetlb() check. The reasons are as follows:
1）If we remove it, we will be unable to obtain the hstat corresponding to the folio, and consequently, we won't be able to call alloc_and_dissolve_hugetlb_folio().
2）The alloc_and_dissolve_hugetlb_folio() function is also called within the isolate_or_dissolve_huge_folio() function. However, the folio_test_hugetlb() check within the isolate_or_dissolve_huge_folio() function cannot be removed.