diff options
| -rw-r--r-- | fs/notify/fdinfo.c | 4 | ||||
| -rw-r--r-- | fs/notify/group.c | 11 | ||||
| -rw-r--r-- | fs/notify/mark.c | 24 | ||||
| -rw-r--r-- | include/linux/fsnotify_backend.h | 28 |
4 files changed, 52 insertions, 15 deletions
diff --git a/fs/notify/fdinfo.c b/fs/notify/fdinfo.c index 3451708fd035..1f34c5c29fdb 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 18446b7b0d49..1de6631a3925 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 1fb246ea6175..982ca2f20ff5 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 dd440e6ff528..d62111e83244 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, |