[PATCH v8 6/8] mm: Introduce mf_dax_kill_procs() for fsdax case

[Shiyang Ruan]

This function is called at the end of RMAP routine, i.e. filesystem
recovery function, to collect and kill processes using a shared page of
DAX file.  The difference between mf_generic_kill_procs() is,
it accepts file's mapping,offset instead of struct page.  Because
different file's mappings and offsets may share the same page in fsdax
mode.  So, it is called when filesystem RMAP results are found.

Signed-off-by: Shiyang Ruan <ruansy.fnst@xxxxxxxxxxx>
---
 fs/dax.c            | 10 ------
 include/linux/dax.h |  9 +++++
 include/linux/mm.h  |  2 ++
 mm/memory-failure.c | 83 ++++++++++++++++++++++++++++++++++++++++-----
 4 files changed, 86 insertions(+), 18 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 59e02c9f169c..7e46569c6129 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -852,16 +852,6 @@ static void *dax_insert_entry(struct xa_state *xas,
 	return entry;
 }
 
-static inline
-unsigned long pgoff_address(pgoff_t pgoff, struct vm_area_struct *vma)
-{
-	unsigned long address;
-
-	address = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
-	VM_BUG_ON_VMA(address < vma->vm_start || address >= vma->vm_end, vma);
-	return address;
-}
-
 /* Walk all mappings of a given index of a file and writeprotect them */
 static void dax_entry_mkclean(struct address_space *mapping, pgoff_t index,
 		unsigned long pfn)
diff --git a/include/linux/dax.h b/include/linux/dax.h
index c78ca4f8285a..e652a5ae3cc0 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -254,6 +254,15 @@ static inline bool dax_mapping(struct address_space *mapping)
 {
 	return mapping->host && IS_DAX(mapping->host);
 }
+static inline unsigned long pgoff_address(pgoff_t pgoff,
+		struct vm_area_struct *vma)
+{
+	unsigned long address;
+
+	address = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
+	VM_BUG_ON_VMA(address < vma->vm_start || address >= vma->vm_end, vma);
+	return address;
+}
 
 #ifdef CONFIG_DEV_DAX_HMEM_DEVICES
 void hmem_register_device(int target_nid, struct resource *r);
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 73a52aba448f..c94ba51e64c1 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -3114,6 +3114,8 @@ enum mf_flags {
 	MF_MUST_KILL = 1 << 2,
 	MF_SOFT_OFFLINE = 1 << 3,
 };
+extern 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 8bf6f54b5705..74059c6f4235 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -302,10 +302,9 @@ void shake_page(struct page *p)
 }
 EXPORT_SYMBOL_GPL(shake_page);
 
-static unsigned long dev_pagemap_mapping_shift(struct page *page,
+static unsigned long dev_pagemap_mapping_shift(unsigned long address,
 		struct vm_area_struct *vma)
 {
-	unsigned long address = vma_address(page, vma);
 	unsigned long ret = 0;
 	pgd_t *pgd;
 	p4d_t *p4d;
@@ -345,7 +344,7 @@ 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.
  */
-static void add_to_kill(struct task_struct *tsk, struct page *p,
+static void add_to_kill(struct task_struct *tsk, struct page *p, pgoff_t pgoff,
 		       struct vm_area_struct *vma,
 		       struct list_head *to_kill)
 {
@@ -358,9 +357,15 @@ 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 no more used for fsdax, we should
+		 * calculate the address in a fsdax way.
+		 */
+		if (p->pgmap->type == MEMORY_DEVICE_FS_DAX)
+			tk->addr = pgoff_address(pgoff, vma);
+		tk->size_shift = dev_pagemap_mapping_shift(tk->addr, vma);
+	} else
 		tk->size_shift = page_shift(compound_head(p));
 
 	/*
@@ -508,7 +513,7 @@ 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);
@@ -544,7 +549,32 @@ 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);
+}
+
+/*
+ * 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);
@@ -1504,6 +1534,43 @@ static int mf_generic_kill_procs(unsigned long long pfn, int flags,
 	return 0;
 }
 
+/**
+ * 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);
+
 static int memory_failure_hugetlb(unsigned long pfn, int flags)
 {
 	struct page *p = pfn_to_page(pfn);
-- 
2.33.0