Re: [PATCH 1/1] jffs2: fix sparse warning: unexpected unlock

[Fabian Frederick]

> On 27 September 2014 at 01:17 josh@xxxxxxxxxxxxxxxx wrote:
>
>
> On Mon, Sep 22, 2014 at 11:12:50AM -0700, Brian Norris wrote:
> > + linux-sparse
> >
> > On Thu, Sep 18, 2014 at 08:46:16PM +0200, Fabian Frederick wrote:
> > > fs/jffs2/summary.c:846:5: warning: context imbalance in
> > > 'jffs2_sum_write_sumnode' - unexpected unlock
> > >
> > > Signed-off-by: Fabian Frederick <fabf@xxxxxxxxx>
> > > ---
> > >Â fs/jffs2/summary.c | 2 ++
> > >Â 1 file changed, 2 insertions(+)
> > >
> > > diff --git a/fs/jffs2/summary.c b/fs/jffs2/summary.c
> > > index c522d09..a0bac7b 100644
> > > --- a/fs/jffs2/summary.c
> > > +++ b/fs/jffs2/summary.c
> > > @@ -844,6 +844,8 @@ static int jffs2_sum_write_data(struct jffs2_sb_info
> > > *c, struct jffs2_eraseblock
> > >Â /* Write out summary information - called from jffs2_do_reserve_space */
> > >Â
> > >Â int jffs2_sum_write_sumnode(struct jffs2_sb_info *c)
> > > + __releases(&c->erase_completion_lock)
> > > + __acquires(&c->erase_completion_lock)
> >
> > I'm not too familiar with sparse notations, but Documentation/sparse.txt
> > suggests the above is wrong, and the following is more accurate:
> >
> >Â Â Â__must_hold(&c->erase_completion_lock)
> >
> > But it looks like there are several other examples which do this.
> > Anyway, here's the relevant doc text, in case someone wants to clarify
> > it for me, or else tell me the documentation is wrong:
> >
> >Â Â Â__must_hold - The specified lock is held on function entry and exit.
> >
> >Â Â Â__acquires - The specified lock is held on function exit, but not entry.
> >
> >Â Â Â__releases - The specified lock is held on function entry, but not exit.
> >
> > So __acquires and __releases look mutually exclusive, but it's not clear
> > if __must_hold will actually cover what we want. (I haven't tested it.)
>
> __must_hold is indeed the correct annotation. (There isn't currently
> anything enforcing that, though.)
>
> - Josh Triplett

There are 137 __releases && __acquires annotated functions in stable.

AFAICS those are based on lock held on function entry / lock held on exit

See
fs/fuse/file.c:1527
fs/kernfs/dir.c:341
drivers/block/nbd.c:564

Does it mean that all of these should be updated to __must_hold ?

Fabian
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