Hi Mike! [added ext4 list to CC] On Tue 06-09-22 18:21:37, Mike Galbraith wrote: > diff --git a/fs/mbcache.c b/fs/mbcache.c > index d1ebb5df2856..96f1d49d30a5 100644 > --- a/fs/mbcache.c > +++ b/fs/mbcache.c > @ -106,21 +106,28 @@ int mb_cache_entry_create(struct mb_cache *cache, gfp_t mask, u32 key, > } > } > hlist_bl_add_head(&entry->e_hash_list, head); > - hlist_bl_unlock(head); > - > + /* > + * Add entry to LRU list before it can be found by > + * mb_cache_entry_delete() to avoid races > + */ > spin_lock(&cache->c_list_lock); > list_add_tail(&entry->e_list, &cache->c_list); > - /* Grab ref for LRU list */ > - atomic_inc(&entry->e_refcnt); > cache->c_entry_count++; > spin_unlock(&cache->c_list_lock); > + hlist_bl_unlock(head); > > return 0; > } > EXPORT_SYMBOL(mb_cache_entry_create); > > The above movement of hlist_bl_unlock() is a problem for RT wrt both > taking and releasing of ->c_list_lock, it becoming an rtmutex in RT and > hlist_bl_unlock() taking a preemption blocking bit spinlock. > > Is that scope increase necessary? If so, looks like ->c_list_lock > could probably become a raw_spinlock_t without anyone noticing. Well, it was an easy solution but there's relatively simple workaround that should remove the need of nesting. I'll send a patch. Honza -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
