linux-kernel - Re: [GIT PULL] bcachefs changes for 6.11, v2

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Message-ID: <da03e2a7-0293-4b28-9a08-6c0fad51b9a3@stanley.mountain>
Date: Tue, 27 Aug 2024 21:25:56 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Kent Overstreet <kent.overstreet@...ux.dev>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-bcachefs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [GIT PULL] bcachefs changes for 6.11, v2

On Tue, Aug 27, 2024 at 12:23:22PM -0400, Kent Overstreet wrote:
> On Tue, Aug 27, 2024 at 01:53:55PM GMT, Dan Carpenter wrote:
> > On Thu, Jul 19, 2024 at 06:36:50PM -0400, Kent Overstreet wrote:
> > >       bcachefs: Unlock trans when waiting for user input in fsck
> > 
> > Hello Kent Overstreet,
> > 
> > ommit 889fb3dc5d6f ("bcachefs: Unlock trans when waiting for user
> > input in fsck") from May 29, 2024 (linux-next), leads to the
> > following (UNPUBLISHED) Smatch static checker warning:
> > 
> > fs/bcachefs/error.c:129 bch2_fsck_ask_yn() error: double unlocked 'trans' (orig line 113)
> > 
> > fs/bcachefs/error.c
> >    102  static enum ask_yn bch2_fsck_ask_yn(struct bch_fs *c, struct btree_trans *trans)
> >    103  {
> >    104          struct stdio_redirect *stdio = c->stdio;
> >    105  
> >    106          if (c->stdio_filter && c->stdio_filter != current)
> >    107                  stdio = NULL;
> >    108  
> >    109          if (!stdio)
> >    110                  return YN_NO;
> >    111  
> >    112          if (trans)
> >    113                  bch2_trans_unlock(trans);
> >                         ^^^^^^^^^^^^^^^^^^^^^^^^^
> > Unlock
> > 
> >    114  
> >    115          unsigned long unlock_long_at = trans ? jiffies + HZ * 2 : 0;
> >    116          darray_char line = {};
> >    117          int ret;
> >    118  
> >    119          do {
> >    120                  unsigned long t;
> >    121                  bch2_print(c, " (y,n, or Y,N for all errors of this type) ");
> >    122  rewait:
> >    123                  t = unlock_long_at
> >    124                          ? max_t(long, unlock_long_at - jiffies, 0)
> >    125                          : MAX_SCHEDULE_TIMEOUT;
> >    126  
> >    127                  int r = bch2_stdio_redirect_readline_timeout(stdio, &line, t);
> >    128                  if (r == -ETIME) {
> >    129                          bch2_trans_unlock_long(trans);
> >                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> > Double unlock
> 
> Those are different types of unlocks.
> 

What tripped the static checker up is that bch2_trans_unlock_long() calls
bch2_trans_unlock().

fs/bcachefs/btree_locking.c
   815  void bch2_trans_unlock_long(struct btree_trans *trans)
   816  {
   817          bch2_trans_unlock(trans);
   818          bch2_trans_srcu_unlock(trans);
   819  }

But looking at it now, I guess if we call bch2_trans_unlock() twice the second
unlock is a no-op.  Thanks!

regards,
dan carpenter