ref_tracker: add a count of untracked references

We are still chasing a netdev refcount imbalance, and we suspect
we have one rogue dev_put() that is consuming a reference taken
from a dev_hold_track()

To detect this case, allow ref_tracker_alloc() and ref_tracker_free()
to be called with a NULL @trackerp parameter, and use a dedicated
refcount_t just for them.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/linux/ref_tracker.h b/include/linux/ref_tracker.h
index a443abd..9ca353a 100644 (file)
--- a/include/linux/ref_tracker.h
+++ b/include/linux/ref_tracker.h
@@ -13,6 +13,7 @@ struct ref_tracker_dir {
        spinlock_t              lock;
        unsigned int            quarantine_avail;
        refcount_t              untracked;
+       refcount_t              no_tracker;
        bool                    dead;
        struct list_head        list; /* List of active trackers */
        struct list_head        quarantine; /* List of dead trackers */
@@ -29,6 +30,7 @@ static inline void ref_tracker_dir_init(struct ref_tracker_dir *dir,
        dir->quarantine_avail = quarantine_count;
        dir->dead = false;
        refcount_set(&dir->untracked, 1);
+       refcount_set(&dir->no_tracker, 1);
        stack_depot_init();
 }
 

diff --git a/lib/ref_tracker.c b/lib/ref_tracker.c
index 32ff6bd..9c0c2e0 100644 (file)
--- a/lib/ref_tracker.c
+++ b/lib/ref_tracker.c
@@ -38,6 +38,7 @@ void ref_tracker_dir_exit(struct ref_tracker_dir *dir)
        spin_unlock_irqrestore(&dir->lock, flags);
        WARN_ON_ONCE(leak);
        WARN_ON_ONCE(refcount_read(&dir->untracked) != 1);
+       WARN_ON_ONCE(refcount_read(&dir->no_tracker) != 1);
 }
 EXPORT_SYMBOL(ref_tracker_dir_exit);
 
@@ -75,6 +76,10 @@ int ref_tracker_alloc(struct ref_tracker_dir *dir,
 
        WARN_ON_ONCE(dir->dead);
 
+       if (!trackerp) {
+               refcount_inc(&dir->no_tracker);
+               return 0;
+       }
        if (gfp & __GFP_DIRECT_RECLAIM)
                gfp_mask |= __GFP_NOFAIL;
        *trackerp = tracker = kzalloc(sizeof(*tracker), gfp_mask);
@@ -98,13 +103,18 @@ int ref_tracker_free(struct ref_tracker_dir *dir,
                     struct ref_tracker **trackerp)
 {
        unsigned long entries[REF_TRACKER_STACK_ENTRIES];
-       struct ref_tracker *tracker = *trackerp;
        depot_stack_handle_t stack_handle;
+       struct ref_tracker *tracker;
        unsigned int nr_entries;
        unsigned long flags;
 
        WARN_ON_ONCE(dir->dead);
 
+       if (!trackerp) {
+               refcount_dec(&dir->no_tracker);
+               return 0;
+       }
+       tracker = *trackerp;
        if (!tracker) {
                refcount_dec(&dir->untracked);
                return -EEXIST;