Re: [PATCH 1/2] fs/xfs: Drop unnecessary NULL test
From: Olaf Weber
Date: Tue Jul 14 2009 - 06:34:54 EST
Julia Lawall writes:
> From: Julia Lawall <julia@xxxxxxx>
> The result of container_of should not be NULL. In particular, in this case
> the argument to the enclosing function has passed though INIT_DELAYED_WORK,
> which dereferences it, implying that its container cannot be NULL.
Given the defn of container_of() it seems clear that neither its input
pointer nor its result should ever be NULL.
In this particular case, there is a check for NULL and early exit in
xfs_mru_cache_create(), the function that does the INIT_DELAYED_WORK().
Olaf
> The semantic match that finds this problem is as follows:
> (http://www.emn.fr/x-info/coccinelle/)
> // <smpl>
> @@
> expression x,e;
> @@
> x = container_of(...)
> ... when != x = e
> * x == NULL
> // </smpl>
> Signed-off-by: Julia Lawall <julia@xxxxxxx>
Acked-By: Olaf Weber <olaf@xxxxxxx>
> ---
> fs/xfs/xfs_mru_cache.c | 4 ++--
> 1 files changed, 2 insertions(+), 2 deletions(-)
> diff --git a/fs/xfs/xfs_mru_cache.c b/fs/xfs/xfs_mru_cache.c
> index 4b0613d..0651ce7 100644
> --- a/fs/xfs/xfs_mru_cache.c
> +++ b/fs/xfs/xfs_mru_cache.c
> @@ -280,8 +280,8 @@ _xfs_mru_cache_reap(
> xfs_mru_cache_t *mru = container_of(work, xfs_mru_cache_t, work.work);
> unsigned long now, next;
> - ASSERT(mru && mru->lists);
> - if (!mru || !mru->lists)
> + ASSERT(mru->lists);
> + if (!mru->lists)
> return;
> spin_lock(&mru->lock);
--
Olaf Weber SGI Phone: +31(0)30-6696752
Veldzigt 2b Fax: +31(0)30-6696799
Technical Lead 3454 PW de Meern Vnet: 955-7151
Storage Software The Netherlands Email: olaf@xxxxxxx
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