mm: memory-failure: add unmap_poisoned_folio()

Add unmap_poisoned_folio() helper which will be reused by
do_migrate_range() from memory hotplug soon.

[akpm@linux-foundation.org: whitespace tweak, per Miaohe Lin]
  Link: https://lkml.kernel.org/r/1f80c7e3-c30d-1ac1-6a36-d1a5f5907f7c@huawei.com
Link: https://lkml.kernel.org/r/20240827114728.3212578-3-wangkefeng.wang@huawei.com
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Dan Carpenter <dan.carpenter@linaro.org>
Cc: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>
Cc: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/internal.h

@@ -1048,6 +1048,8 @@ static inline int find_next_best_node(int node, nodemask_t *used_node_mask)
 /*
  * mm/memory-failure.c
  */
+#ifdef CONFIG_MEMORY_FAILURE
+void unmap_poisoned_folio(struct folio *folio, enum ttu_flags ttu);
 void shake_folio(struct folio *folio);
 extern int hwpoison_filter(struct page *p);
 
@@ -1068,6 +1070,12 @@ void add_to_kill_ksm(struct task_struct *tsk, struct page *p,
 		     unsigned long ksm_addr);
 unsigned long page_mapped_in_vma(struct page *page, struct vm_area_struct *vma);
 
+#else
+static inline void unmap_poisoned_folio(struct folio *folio, enum ttu_flags ttu)
+{
+}
+#endif
+
 extern unsigned long  __must_check vm_mmap_pgoff(struct file *, unsigned long,
         unsigned long, unsigned long,
         unsigned long, unsigned long);

mm/memory-failure.c

@@ -1554,6 +1554,32 @@ static int get_hwpoison_page(struct page *p, unsigned long flags)
 	return ret;
 }
 
+void unmap_poisoned_folio(struct folio *folio, enum ttu_flags ttu)
+{
+	if (folio_test_hugetlb(folio) && !folio_test_anon(folio)) {
+		struct address_space *mapping;
+
+		/*
+		 * For hugetlb folios in shared mappings, try_to_unmap
+		 * could potentially call huge_pmd_unshare.  Because of
+		 * this, take semaphore in write mode here and set
+		 * TTU_RMAP_LOCKED to indicate we have taken the lock
+		 * at this higher level.
+		 */
+		mapping = hugetlb_folio_mapping_lock_write(folio);
+		if (!mapping) {
+			pr_info("%#lx: could not lock mapping for mapped hugetlb folio\n",
+				folio_pfn(folio));
+			return;
+		}
+
+		try_to_unmap(folio, ttu|TTU_RMAP_LOCKED);
+		i_mmap_unlock_write(mapping);
+	} else {
+		try_to_unmap(folio, ttu);
+	}
+}
+
 /*
  * Do all that is necessary to remove user space mappings. Unmap
  * the pages and send SIGBUS to the processes if the data was dirty.
@@ -1615,23 +1641,7 @@ static bool hwpoison_user_mappings(struct folio *folio, struct page *p,
 	 */
 	collect_procs(folio, p, &tokill, flags & MF_ACTION_REQUIRED);
 
-	if (folio_test_hugetlb(folio) && !folio_test_anon(folio)) {
-		/*
-		 * For hugetlb pages in shared mappings, try_to_unmap
-		 * could potentially call huge_pmd_unshare.  Because of
-		 * this, take semaphore in write mode here and set
-		 * TTU_RMAP_LOCKED to indicate we have taken the lock
-		 * at this higher level.
-		 */
-		mapping = hugetlb_folio_mapping_lock_write(folio);
-		if (mapping) {
-			try_to_unmap(folio, ttu|TTU_RMAP_LOCKED);
-			i_mmap_unlock_write(mapping);
-		} else
-			pr_info("%#lx: could not lock mapping for mapped huge page\n", pfn);
-	} else {
-		try_to_unmap(folio, ttu);
-	}
+	unmap_poisoned_folio(folio, ttu);
 
 	unmap_success = !folio_mapped(folio);
 	if (!unmap_success)