diff --git a/fs/notify/fdinfo.c b/fs/notify/fdinfo.c
index 3451708fd035c86b662791c9033bf91659b4443e..1f34c5c29fdbd9aa7f6b62ac31fcb0913725388f 100644
--- a/fs/notify/fdinfo.c
+++ b/fs/notify/fdinfo.c
@@ -28,13 +28,13 @@ static void show_fdinfo(struct seq_file *m, struct file *f,
struct fsnotify_group *group = f->private_data;
struct fsnotify_mark *mark;
- mutex_lock(&group->mark_mutex);
+ fsnotify_group_lock(group);
list_for_each_entry(mark, &group->marks_list, g_list) {
show(m, mark);
if (seq_has_overflowed(m))
break;
}
- mutex_unlock(&group->mark_mutex);
+ fsnotify_group_unlock(group);
}
#if defined(CONFIG_EXPORTFS)
diff --git a/fs/notify/group.c b/fs/notify/group.c
index 18446b7b0d495d64af470e0b598c6f2c492939ce..1de6631a3925ee99266fe5516de5c3669c8385b3 100644
--- a/fs/notify/group.c
+++ b/fs/notify/group.c
@@ -115,6 +115,7 @@ static struct fsnotify_group *__fsnotify_alloc_group(
const struct fsnotify_ops *ops,
int flags, gfp_t gfp)
{
+ static struct lock_class_key nofs_marks_lock;
struct fsnotify_group *group;
group = kzalloc(sizeof(struct fsnotify_group), gfp);
@@ -135,6 +136,16 @@ static struct fsnotify_group *__fsnotify_alloc_group(
group->ops = ops;
group->flags = flags;
+ /*
+ * For most backends, eviction of inode with a mark is not expected,
+ * because marks hold a refcount on the inode against eviction.
+ *
+ * Use a different lockdep class for groups that support evictable
+ * inode marks, because with evictable marks, mark_mutex is NOT
+ * fs-reclaim safe - the mutex is taken when evicting inodes.
+ */
+ if (flags & FSNOTIFY_GROUP_NOFS)
+ lockdep_set_class(&group->mark_mutex, &nofs_marks_lock);
return group;
}
diff --git a/fs/notify/mark.c b/fs/notify/mark.c
index 1fb246ea6175243ff9ef07eb2bd73a8341892553..982ca2f20ff5dba067840545f11806dabbbf9f08 100644
--- a/fs/notify/mark.c
+++ b/fs/notify/mark.c
@@ -398,9 +398,7 @@ void fsnotify_finish_user_wait(struct fsnotify_iter_info *iter_info)
*/
void fsnotify_detach_mark(struct fsnotify_mark *mark)
{
- struct fsnotify_group *group = mark->group;
-
- WARN_ON_ONCE(!mutex_is_locked(&group->mark_mutex));
+ fsnotify_group_assert_locked(mark->group);
WARN_ON_ONCE(!srcu_read_lock_held(&fsnotify_mark_srcu) &&
refcount_read(&mark->refcnt) < 1 +
!!(mark->flags & FSNOTIFY_MARK_FLAG_ATTACHED));
@@ -452,9 +450,9 @@ void fsnotify_free_mark(struct fsnotify_mark *mark)
void fsnotify_destroy_mark(struct fsnotify_mark *mark,
struct fsnotify_group *group)
{
- mutex_lock(&group->mark_mutex);
+ fsnotify_group_lock(group);
fsnotify_detach_mark(mark);
- mutex_unlock(&group->mark_mutex);
+ fsnotify_group_unlock(group);
fsnotify_free_mark(mark);
}
EXPORT_SYMBOL_GPL(fsnotify_destroy_mark);
@@ -673,7 +671,7 @@ int fsnotify_add_mark_locked(struct fsnotify_mark *mark,
struct fsnotify_group *group = mark->group;
int ret = 0;
- BUG_ON(!mutex_is_locked(&group->mark_mutex));
+ fsnotify_group_assert_locked(group);
/*
* LOCKING ORDER!!!!
@@ -714,9 +712,9 @@ int fsnotify_add_mark(struct fsnotify_mark *mark, fsnotify_connp_t *connp,
int ret;
struct fsnotify_group *group = mark->group;
- mutex_lock(&group->mark_mutex);
+ fsnotify_group_lock(group);
ret = fsnotify_add_mark_locked(mark, connp, obj_type, add_flags, fsid);
- mutex_unlock(&group->mark_mutex);
+ fsnotify_group_unlock(group);
return ret;
}
EXPORT_SYMBOL_GPL(fsnotify_add_mark);
@@ -770,24 +768,24 @@ void fsnotify_clear_marks_by_group(struct fsnotify_group *group,
* move marks to free to to_free list in one go and then free marks in
* to_free list one by one.
*/
- mutex_lock(&group->mark_mutex);
+ fsnotify_group_lock(group);
list_for_each_entry_safe(mark, lmark, &group->marks_list, g_list) {
if (mark->connector->type == obj_type)
list_move(&mark->g_list, &to_free);
}
- mutex_unlock(&group->mark_mutex);
+ fsnotify_group_unlock(group);
clear:
while (1) {
- mutex_lock(&group->mark_mutex);
+ fsnotify_group_lock(group);
if (list_empty(head)) {
- mutex_unlock(&group->mark_mutex);
+ fsnotify_group_unlock(group);
break;
}
mark = list_first_entry(head, struct fsnotify_mark, g_list);
fsnotify_get_mark(mark);
fsnotify_detach_mark(mark);
- mutex_unlock(&group->mark_mutex);
+ fsnotify_group_unlock(group);
fsnotify_free_mark(mark);
fsnotify_put_mark(mark);
}
diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
index dd440e6ff5285301591d703fe12376aaac46ee86..d62111e8324409ebe8528cb6837471df77f7b568 100644
--- a/include/linux/fsnotify_backend.h
+++ b/include/linux/fsnotify_backend.h
@@ -20,6 +20,7 @@
#include <linux/user_namespace.h>
#include <linux/refcount.h>
#include <linux/mempool.h>
+#include <linux/sched/mm.h>
/*
* IN_* from inotfy.h lines up EXACTLY with FS_*, this is so we can easily
@@ -212,7 +213,9 @@ struct fsnotify_group {
#define FSNOTIFY_GROUP_USER 0x01 /* user allocated group */
#define FSNOTIFY_GROUP_DUPS 0x02 /* allow multiple marks per object */
+#define FSNOTIFY_GROUP_NOFS 0x04 /* group lock is not direct reclaim safe */
int flags;
+ unsigned int owner_flags; /* stored flags of mark_mutex owner */
/* stores all fastpath marks assoc with this group so they can be cleaned on unregister */
struct mutex mark_mutex; /* protect marks_list */
@@ -254,6 +257,31 @@ struct fsnotify_group {
};
};
+/*
+ * These helpers are used to prevent deadlock when reclaiming inodes with
+ * evictable marks of the same group that is allocating a new mark.
+ */
+static inline void fsnotify_group_lock(struct fsnotify_group *group)
+{
+ mutex_lock(&group->mark_mutex);
+ if (group->flags & FSNOTIFY_GROUP_NOFS)
+ group->owner_flags = memalloc_nofs_save();
+}
+
+static inline void fsnotify_group_unlock(struct fsnotify_group *group)
+{
+ if (group->flags & FSNOTIFY_GROUP_NOFS)
+ memalloc_nofs_restore(group->owner_flags);
+ mutex_unlock(&group->mark_mutex);
+}
+
+static inline void fsnotify_group_assert_locked(struct fsnotify_group *group)
+{
+ WARN_ON_ONCE(!mutex_is_locked(&group->mark_mutex));
+ if (group->flags & FSNOTIFY_GROUP_NOFS)
+ WARN_ON_ONCE(!(current->flags & PF_MEMALLOC_NOFS));
+}
+
/* When calling fsnotify tell it if the data is a path or inode */
enum fsnotify_data_type {
FSNOTIFY_EVENT_NONE,