2014-07-08 22:21:49

by Himangi Saraogi

Subject: [PATCH] Btrfs: use BUG_ON

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>

Signed-off-by: Himangi Saraogi <[email protected]>
Acked-by: Julia Lawall <[email protected]>
---
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)
--
1.9.1

2014-07-10 00:16:18

by Satoru Takeuchi

Subject: Re: [PATCH] Btrfs: use BUG_ON

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)) {
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 <[email protected]>
> Acked-by: Julia Lawall <[email protected]>
> ---
> 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)
>

2014-07-10 05:56:52

by Julia Lawall

Subject: Re: [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 <[email protected]>
> > Acked-by: Julia Lawall <[email protected]>
> > ---
> > 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)
> >
>
>