mm/memory-failure: teach kill_accessing_process to accept hugetlb tail page pfn

When a hugetlb folio is being poisoned again, try_memory_failure_hugetlb()
passed head pfn to kill_accessing_process(), that is not right.  The
precise pfn of the poisoned page should be used in order to determine the
precise vaddr as the SIGBUS payload.

This issue has already been taken care of in the normal path, that is,
hwpoison_user_mappings(), see [1][2].  Further more, for [3] to work
correctly in the hugetlb repoisoning case, it's essential to inform VM the
precise poisoned page, not the head page.

[1] https://lkml.kernel.org/r/20231218135837.3310403-1-willy@infradead.org
[2] https://lkml.kernel.org/r/20250224211445.2663312-1-jane.chu@oracle.com
[3] https://lore.kernel.org/lkml/20251116013223.1557158-1-jiaqiyan@google.com/

Link: https://lkml.kernel.org/r/20260120232234.3462258-2-jane.chu@oracle.com
Signed-off-by: Jane Chu <jane.chu@oracle.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Acked-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Chris Mason <clm@meta.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Jiaqi Yan <jiaqiyan@google.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: William Roche <william.roche@oracle.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: jchu314atgithub

mm/memory-failure.c

@@ -692,6 +692,8 @@ static int check_hwpoisoned_entry(pte_t pte, unsigned long addr, short shift,
 				unsigned long poisoned_pfn, struct to_kill *tk)
 {
 	unsigned long pfn = 0;
+	unsigned long hwpoison_vaddr;
+	unsigned long mask;
 
 	if (pte_present(pte)) {
 		pfn = pte_pfn(pte);
@@ -702,10 +704,12 @@ static int check_hwpoisoned_entry(pte_t pte, unsigned long addr, short shift,
 			pfn = softleaf_to_pfn(entry);
 	}
 
-	if (!pfn || pfn != poisoned_pfn)
+	mask = ~((1UL << (shift - PAGE_SHIFT)) - 1);
+	if (!pfn || pfn != (poisoned_pfn & mask))
 		return 0;
 
-	set_to_kill(tk, addr, shift);
+	hwpoison_vaddr = addr + ((poisoned_pfn - pfn) << PAGE_SHIFT);
+	set_to_kill(tk, hwpoison_vaddr, shift);
 	return 1;
 }
 
@@ -2052,10 +2056,8 @@ static int try_memory_failure_hugetlb(unsigned long pfn, int flags, int *hugetlb
 	case MF_HUGETLB_FOLIO_PRE_POISONED:
 	case MF_HUGETLB_PAGE_PRE_POISONED:
 		rv = -EHWPOISON;
-		if (flags & MF_ACTION_REQUIRED) {
-			folio = page_folio(p);
-			rv = kill_accessing_process(current, folio_pfn(folio), flags);
-		}
+		if (flags & MF_ACTION_REQUIRED)
+			rv = kill_accessing_process(current, pfn, flags);
 		if (res == MF_HUGETLB_PAGE_PRE_POISONED)
 			action_result(pfn, MF_MSG_ALREADY_POISONED, MF_FAILED);
 		else