[PATCH v12 5/7] mm: Introduce mf_dax_kill_procs() for fsdax case

[Shiyang Ruan]

This new function is a variant of mf_generic_kill_procs that accepts a
file, offset pair instead o a struct to support multiple files sharing a
DAX mapping.  It is intended to be called by the file systems as part of
the memory_failure handler after the file system performed a reverse
mapping from the storage address to the file and file offset.

Signed-off-by: Shiyang Ruan <ruansy.fnst@xxxxxxxxxxx>
Reviewed-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
---
 include/linux/mm.h  |  2 +
 mm/memory-failure.c | 96 ++++++++++++++++++++++++++++++++++++++++-----
 2 files changed, 88 insertions(+), 10 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index e0ad13486035..742604feef28 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -3226,6 +3226,8 @@ enum mf_flags {
 	MF_SOFT_OFFLINE = 1 << 3,
 	MF_UNPOISON = 1 << 4,
 };
+int mf_dax_kill_procs(struct address_space *mapping, pgoff_t index,
+		      unsigned long count, int mf_flags);
 extern int memory_failure(unsigned long pfn, int flags);
 extern void memory_failure_queue(unsigned long pfn, int flags);
 extern void memory_failure_queue_kick(int cpu);
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index c8c898669c75..0664115c570b 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -295,10 +295,9 @@ void shake_page(struct page *p)
 }
 EXPORT_SYMBOL_GPL(shake_page);
 
-static unsigned long dev_pagemap_mapping_shift(struct page *page,
-		struct vm_area_struct *vma)
+static unsigned long dev_pagemap_mapping_shift(struct vm_area_struct *vma,
+		unsigned long address)
 {
-	unsigned long address = vma_address(page, vma);
 	unsigned long ret = 0;
 	pgd_t *pgd;
 	p4d_t *p4d;
@@ -338,10 +337,14 @@ static unsigned long dev_pagemap_mapping_shift(struct page *page,
 /*
  * Schedule a process for later kill.
  * Uses GFP_ATOMIC allocations to avoid potential recursions in the VM.
+ *
+ * Notice: @fsdax_pgoff is used only when @p is a fsdax page.
+ *   In other cases, such as anonymous and file-backend page, the address to be
+ *   killed can be caculated by @p itself.
  */
 static void add_to_kill(struct task_struct *tsk, struct page *p,
-		       struct vm_area_struct *vma,
-		       struct list_head *to_kill)
+			pgoff_t fsdax_pgoff, struct vm_area_struct *vma,
+			struct list_head *to_kill)
 {
 	struct to_kill *tk;
 
@@ -352,9 +355,15 @@ static void add_to_kill(struct task_struct *tsk, struct page *p,
 	}
 
 	tk->addr = page_address_in_vma(p, vma);
-	if (is_zone_device_page(p))
-		tk->size_shift = dev_pagemap_mapping_shift(p, vma);
-	else
+	if (is_zone_device_page(p)) {
+		/*
+		 * Since page->mapping is not used for fsdax, we need
+		 * calculate the address based on the vma.
+		 */
+		if (p->pgmap->type == MEMORY_DEVICE_FS_DAX)
+			tk->addr = vma_pgoff_address(fsdax_pgoff, 1, vma);
+		tk->size_shift = dev_pagemap_mapping_shift(vma, tk->addr);
+	} else
 		tk->size_shift = page_shift(compound_head(p));
 
 	/*
@@ -503,7 +512,7 @@ static void collect_procs_anon(struct page *page, struct list_head *to_kill,
 			if (!page_mapped_in_vma(page, vma))
 				continue;
 			if (vma->vm_mm == t->mm)
-				add_to_kill(t, page, vma, to_kill);
+				add_to_kill(t, page, 0, vma, to_kill);
 		}
 	}
 	read_unlock(&tasklist_lock);
@@ -539,13 +548,41 @@ static void collect_procs_file(struct page *page, struct list_head *to_kill,
 			 * to be informed of all such data corruptions.
 			 */
 			if (vma->vm_mm == t->mm)
-				add_to_kill(t, page, vma, to_kill);
+				add_to_kill(t, page, 0, vma, to_kill);
 		}
 	}
 	read_unlock(&tasklist_lock);
 	i_mmap_unlock_read(mapping);
 }
 
+#if IS_ENABLED(CONFIG_FS_DAX)
+/*
+ * Collect processes when the error hit a fsdax page.
+ */
+static void collect_procs_fsdax(struct page *page,
+		struct address_space *mapping, pgoff_t pgoff,
+		struct list_head *to_kill)
+{
+	struct vm_area_struct *vma;
+	struct task_struct *tsk;
+
+	i_mmap_lock_read(mapping);
+	read_lock(&tasklist_lock);
+	for_each_process(tsk) {
+		struct task_struct *t = task_early_kill(tsk, true);
+
+		if (!t)
+			continue;
+		vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
+			if (vma->vm_mm == t->mm)
+				add_to_kill(t, page, pgoff, vma, to_kill);
+		}
+	}
+	read_unlock(&tasklist_lock);
+	i_mmap_unlock_read(mapping);
+}
+#endif /* CONFIG_FS_DAX */
+
 /*
  * Collect the processes who have the corrupted page mapped to kill.
  */
@@ -1583,6 +1620,45 @@ static int mf_generic_kill_procs(unsigned long long pfn, int flags,
 	return 0;
 }
 
+#ifdef CONFIG_FS_DAX
+/**
+ * mf_dax_kill_procs - Collect and kill processes who are using this file range
+ * @mapping:	the file in use
+ * @index:	start pgoff of the range within the file
+ * @count:	length of the range, in unit of PAGE_SIZE
+ * @mf_flags:	memory failure flags
+ */
+int mf_dax_kill_procs(struct address_space *mapping, pgoff_t index,
+		unsigned long count, int mf_flags)
+{
+	LIST_HEAD(to_kill);
+	dax_entry_t cookie;
+	struct page *page;
+	size_t end = index + count;
+
+	mf_flags |= MF_ACTION_REQUIRED | MF_MUST_KILL;
+
+	for (; index < end; index++) {
+		page = NULL;
+		cookie = dax_lock_mapping_entry(mapping, index, &page);
+		if (!cookie)
+			return -EBUSY;
+		if (!page)
+			goto unlock;
+
+		SetPageHWPoison(page);
+
+		collect_procs_fsdax(page, mapping, index, &to_kill);
+		unmap_and_kill(&to_kill, page_to_pfn(page), mapping,
+				index, mf_flags);
+unlock:
+		dax_unlock_mapping_entry(mapping, index, cookie);
+	}
+	return 0;
+}
+EXPORT_SYMBOL_GPL(mf_dax_kill_procs);
+#endif /* CONFIG_FS_DAX */
+
 /*
  * Called from hugetlb code with hugetlb_lock held.
  * If a hugepage is successfully grabbed (so it's determined to handle
-- 
2.35.1