linux-kernel - Re: [PATCH] btrfs: fiemap: make the assert more explicit after handling the error cases

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Message-ID: <CAPjX3FcVq3FTBxmQkr3QZR3GL6AG7DkKH1SeZ5hQ1JXBN=fo=g@mail.gmail.com>
Date: Wed, 23 Apr 2025 11:58:57 +0200
From: Daniel Vacek <neelx@...e.com>
To: Filipe Manana <fdmanana@...nel.org>
Cc: Chris Mason <clm@...com>, Josef Bacik <josef@...icpanda.com>, David Sterba <dsterba@...e.com>, 
	linux-btrfs@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] btrfs: fiemap: make the assert more explicit after
 handling the error cases

On Wed, 23 Apr 2025 at 11:55, Filipe Manana <fdmanana@...nel.org> wrote:
>
> On Wed, Apr 23, 2025 at 10:48 AM Daniel Vacek <neelx@...e.com> wrote:
> >
> > On Wed, 23 Apr 2025 at 11:04, Filipe Manana <fdmanana@...nel.org> wrote:
> > >
> > > On Wed, Apr 23, 2025 at 9:10 AM Daniel Vacek <neelx@...e.com> wrote:
> > > >
> > > > Let's not assert the errors and clearly state the expected result only
> > > > after eventual error handling. It makes a bit more sense this way.
> > >
> > > It doesn't make more sense to me...
> > > I prefer to assert expected results right after the function call.
> >
> > Oh well, if an error is expected then I get it. Is an error likely
> > here?
>
> The assertion serves to state what is never expected, and not what is
> likely or unlikely.
> It's about stating that an exact match shouldn't happen, i.e. ret == 0.
>
> We do this sort of asserts in many places, and I find it more clear this way.

I see. Forget it then.

Thanks.

> > I understood the comment says there can't be a file extent item
> > at offset (u64)-1 which implies a strict return value of 1 and not an
> > error or something >1. So that's why. And it's still quite after the
> > function call.
> >
> > But I'm happy to scratch it if you don't like it.
> >
> > > Thanks.
> > >
> > > >
> > > > Signed-off-by: Daniel Vacek <neelx@...e.com>
> > > > ---
> > > >  fs/btrfs/fiemap.c | 4 ++--
> > > >  1 file changed, 2 insertions(+), 2 deletions(-)
> > > >
> > > > diff --git a/fs/btrfs/fiemap.c b/fs/btrfs/fiemap.c
> > > > index b80c07ad8c5e7..034f832e10c1a 100644
> > > > --- a/fs/btrfs/fiemap.c
> > > > +++ b/fs/btrfs/fiemap.c
> > > > @@ -568,10 +568,10 @@ static int fiemap_find_last_extent_offset(struct btrfs_inode *inode,
> > > >          * there might be preallocation past i_size.
> > > >          */
> > > >         ret = btrfs_lookup_file_extent(NULL, root, path, ino, (u64)-1, 0);
> > > > -       /* There can't be a file extent item at offset (u64)-1 */
> > > > -       ASSERT(ret != 0);
> > > >         if (ret < 0)
> > > >                 return ret;
> > > > +       /* There can't be a file extent item at offset (u64)-1 */
> > > > +       ASSERT(ret == 1);
> > > >
> > > >         /*
> > > >          * For a non-existing key, btrfs_search_slot() always leaves us at a
> > > > --
> > > > 2.47.2
> > > >
> > > >