On Tue, Mar 26, 2024 at 02:04:50PM +0800, Hongbo Li wrote:
> Do you mean to add these assertions at the end of
> bkey_cached_move_to_freelist and bkey_cached_alloc?
Assertions like this I generally put in the shutdown path - would that
have caught this bug?
If it wouldn't, we could make it a debug mode assertion - probably also
randomly 1/128th of the time or somoesuch, this will be a bit of an
expensive one otherwise
>
> On 2024/3/26 12:17, Kent Overstreet wrote:
> > On Tue, Mar 26, 2024 at 12:04:56PM +0800, Hongbo Li wrote:
> > > When allocating bkey_cached from bc->freed_pcpu list, it missed
> > > decreasing the count of nr_freed_pcpu which would cause the mismatch
> > > between the value of nr_freed_pcpu and the list items. This problem
> > > also exists in moving new bkey_cached to bc->freed_pcpu list.
> > > If these happened, the bug info may appear in
> > > bch2_fs_btree_key_cache_exit by the follow code:
> > >
> > > BUG_ON(list_count_nodes(&bc->freed_pcpu) != bc->nr_freed_pcpu);
> > > BUG_ON(list_count_nodes(&bc->freed_nonpcpu) != bc->nr_freed_nonpcpu);
> >
> > Please include the assertions too :)
> >
> > > Fixes: c65c13f0eac6 ("bcachefs: Run btree key cache shrinker less
> > > aggressively")
> > > Signed-off-by: Hongbo Li <[email protected]>
> > > ---
> > > fs/bcachefs/btree_key_cache.c | 2 ++
> > > 1 file changed, 2 insertions(+)
> > >
> > > diff --git a/fs/bcachefs/btree_key_cache.c b/fs/bcachefs/btree_key_cache.c
> > > index 581edcb0911b..e1031b9ba3f4 100644
> > > --- a/fs/bcachefs/btree_key_cache.c
> > > +++ b/fs/bcachefs/btree_key_cache.c
> > > @@ -169,6 +169,7 @@ static void bkey_cached_move_to_freelist(struct
> > > btree_key_cache *bc,
> > > } else {
> > > mutex_lock(&bc->lock);
> > > list_move_tail(&ck->list, &bc->freed_pcpu);
> > > + bc->nr_freed_pcpu++;
> > > mutex_unlock(&bc->lock);
> > > }
> > > }
> > > @@ -245,6 +246,7 @@ bkey_cached_alloc(struct btree_trans *trans, struct
> > > btree_path *path,
> > > if (!list_empty(&bc->freed_pcpu)) {
> > > ck = list_last_entry(&bc->freed_pcpu, struct
> > > bkey_cached, list);
> > > list_del_init(&ck->list);
> > > + bc->nr_freed_pcpu--;
> > > }
> > > mutex_unlock(&bc->lock);
> > > }
> > > --
> > > 2.34.1
> > >
> >
