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Subject[RFC PATCH 2/8] mm: add dax-rmap for memory-failure and rmap
Date
Memory-failure collects and kill processes who is accessing a posioned,
file mmapped page. Add dax-rmap iteration to support reflink case.
Also add it for rmap iteration.

Signed-off-by: Shiyang Ruan <ruansy.fnst@cn.fujitsu.com>
---
mm/memory-failure.c | 63 +++++++++++++++++++++++++++++++++++----------
mm/rmap.c | 54 +++++++++++++++++++++++++++-----------
2 files changed, 88 insertions(+), 29 deletions(-)

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index a96364be8ab4..6d7da1fd55fd 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -463,36 +463,71 @@ static void collect_procs_anon(struct page *page, struct list_head *to_kill,
page_unlock_anon_vma_read(av);
}

+static void collect_each_procs_file(struct page *page,
+ struct task_struct *task,
+ struct list_head *to_kill)
+{
+ struct vm_area_struct *vma;
+ struct address_space *mapping = page->mapping;
+ struct rb_root_cached *root = (struct rb_root_cached *)page_private(page);
+ struct rb_node *node;
+ struct shared_file *shared;
+ pgoff_t pgoff;
+
+ if (dax_mapping(mapping) && root) {
+ struct shared_file save = {
+ .mapping = mapping,
+ .index = page->index,
+ };
+ for (node = rb_first_cached(root); node; node = rb_next(node)) {
+ shared = container_of(node, struct shared_file, node);
+ mapping = page->mapping = shared->mapping;
+ page->index = shared->index;
+ pgoff = page_to_pgoff(page);
+ vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff,
+ pgoff) {
+ if (vma->vm_mm == task->mm) {
+ // each vma is unique, so is the vaddr.
+ add_to_kill(task, page, vma, to_kill);
+ }
+ }
+ }
+ // restore the mapping and index.
+ page->mapping = save.mapping;
+ page->index = save.index;
+ } else {
+ pgoff = page_to_pgoff(page);
+ vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
+ /*
+ * Send early kill signal to tasks where a vma covers
+ * the page but the corrupted page is not necessarily
+ * mapped it in its pte.
+ * Assume applications who requested early kill want
+ * to be informed of all such data corruptions.
+ */
+ if (vma->vm_mm == task->mm)
+ add_to_kill(task, page, vma, to_kill);
+ }
+ }
+}
+
/*
* Collect processes when the error hit a file mapped page.
*/
static void collect_procs_file(struct page *page, struct list_head *to_kill,
int force_early)
{
- struct vm_area_struct *vma;
struct task_struct *tsk;
struct address_space *mapping = page->mapping;

i_mmap_lock_read(mapping);
read_lock(&tasklist_lock);
for_each_process(tsk) {
- pgoff_t pgoff = page_to_pgoff(page);
struct task_struct *t = task_early_kill(tsk, force_early);

if (!t)
continue;
- vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff,
- pgoff) {
- /*
- * Send early kill signal to tasks where a vma covers
- * the page but the corrupted page is not necessarily
- * mapped it in its pte.
- * Assume applications who requested early kill want
- * to be informed of all such data corruptions.
- */
- if (vma->vm_mm == t->mm)
- add_to_kill(t, page, vma, to_kill);
- }
+ collect_each_procs_file(page, t, to_kill);
}
read_unlock(&tasklist_lock);
i_mmap_unlock_read(mapping);
diff --git a/mm/rmap.c b/mm/rmap.c
index f79a206b271a..69ea66f9e971 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1870,21 +1870,7 @@ static void rmap_walk_anon(struct page *page, struct rmap_walk_control *rwc,
anon_vma_unlock_read(anon_vma);
}

-/*
- * rmap_walk_file - do something to file page using the object-based rmap method
- * @page: the page to be handled
- * @rwc: control variable according to each walk type
- *
- * Find all the mappings of a page using the mapping pointer and the vma chains
- * contained in the address_space struct it points to.
- *
- * When called from try_to_munlock(), the mmap_sem of the mm containing the vma
- * where the page was found will be held for write. So, we won't recheck
- * vm_flags for that VMA. That should be OK, because that vma shouldn't be
- * LOCKED.
- */
-static void rmap_walk_file(struct page *page, struct rmap_walk_control *rwc,
- bool locked)
+static void rmap_walk_file_one(struct page *page, struct rmap_walk_control *rwc, bool locked)
{
struct address_space *mapping = page_mapping(page);
pgoff_t pgoff_start, pgoff_end;
@@ -1925,6 +1911,44 @@ static void rmap_walk_file(struct page *page, struct rmap_walk_control *rwc,
i_mmap_unlock_read(mapping);
}

+/*
+ * rmap_walk_file - do something to file page using the object-based rmap method
+ * @page: the page to be handled
+ * @rwc: control variable according to each walk type
+ *
+ * Find all the mappings of a page using the mapping pointer and the vma chains
+ * contained in the address_space struct it points to.
+ *
+ * When called from try_to_munlock(), the mmap_sem of the mm containing the vma
+ * where the page was found will be held for write. So, we won't recheck
+ * vm_flags for that VMA. That should be OK, because that vma shouldn't be
+ * LOCKED.
+ */
+static void rmap_walk_file(struct page *page, struct rmap_walk_control *rwc,
+ bool locked)
+{
+ struct rb_root_cached *root = (struct rb_root_cached *)page_private(page);
+ struct rb_node *node;
+ struct shared_file *shared;
+
+ if (dax_mapping(page->mapping) && root) {
+ struct shared_file save = {
+ .mapping = page->mapping,
+ .index = page->index,
+ };
+ for (node = rb_first_cached(root); node; node = rb_next(node)) {
+ shared = container_of(node, struct shared_file, node);
+ page->mapping = shared->mapping;
+ page->index = shared->index;
+ rmap_walk_file_one(page, rwc, locked);
+ }
+ // restore the mapping and index.
+ page->mapping = save.mapping;
+ page->index = save.index;
+ } else
+ rmap_walk_file_one(page, rwc, locked);
+}
+
void rmap_walk(struct page *page, struct rmap_walk_control *rwc)
{
if (unlikely(PageKsm(page)))
--
2.26.2


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