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SubjectRe: [PATCH] Btrfs: use BUG_ON


On Thu, 10 Jul 2014, Satoru Takeuchi wrote:

> Hi Himangi,
>
> (2014/07/09 7:21), Himangi Saraogi wrote:
> > Use BUG_ON(x) rather than if(x) BUG();
> >
> > The semantic patch that fixes this problem is as follows:
> >
> > // <smpl>
> > @@ identifier x; @@
> > -if (x) BUG();
> > +BUG_ON(x);
> > // </smpl>
>
> Strictly speaking, BUG_ON() is "if (unlikely(x)) BUG".
> Anyway, I consider that put this condition in unlikely()
> in this case is good.
>
> BTW, there are many "if BUG()" case under fs/btrfs.
> How about fix all of them?
>
> ===============================================================================
> $ grep -rnH -B 1 "BUG()" fs/btrfs | grep -A 1 'if.*('
> fs/btrfs/inode.c-6318- } else if (create && PageUptodate(page)) {

In the past, BUG_ON (and BUG) could have a definition that would just do
nothing. In that case, the call to PageUptodate would go away. The
function may do a read barrier, so that could be undesirable.

But now I don't see any definition of BUG_ON that discards the condition.
So Himangi, you can discard the requirement that the tested expression be
an identifier in the semantic patch, and just allow any expression:

-if(e) BUG();
+BUG_ON(e);

julia

> fs/btrfs/inode.c:6319: BUG();
> --
> fs/btrfs/volumes.c-2626- else if (ret)
> fs/btrfs/volumes.c:2627: BUG(); # <- your patch
> fixes it.
> --
> fs/btrfs/volumes.c-3092- if (ret == 0)
> fs/btrfs/volumes.c:3093: BUG(); /* FIXME break ? */
> --
> fs/btrfs/raid56.c-2048- if (rbio->faila == -1) {
> fs/btrfs/raid56.c:2049: BUG();
> ===============================================================================
>
> Thanks,
> Satoru
>
> >
> > Signed-off-by: Himangi Saraogi <himangi774@gmail.com>
> > Acked-by: Julia Lawall <julia.lawall@lip6.fr>
> > ---
> > fs/btrfs/volumes.c | 4 ++--
> > 1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> > index 6104676..63e746e 100644
> > --- a/fs/btrfs/volumes.c
> > +++ b/fs/btrfs/volumes.c
> > @@ -2623,8 +2623,8 @@ again:
> > found_key.offset);
> > if (ret == -ENOSPC)
> > failed++;
> > - else if (ret)
> > - BUG();
> > + else
> > + BUG_ON(ret);
> > }
> >
> > if (found_key.offset == 0)
> >
>
>


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