Re: Assuming NULL

[Måns Rullgård]

Jan Engelhardt <jengelh@xxxxxxxxxxxxxxx> writes:

> Hi developers,
>
> some places in fs/*.c have conditions like
>
> (namei.c, 238, in "int permission()"):
>         if(inode->i_op && inode->i_op->permission)
>
> Others just have
> (namei.c, 813, in "int fastcall link_path_walk()"):
>         if(!inode->i_op->lookup)
>
> My question is: Which one is right wrt the case "i_op ==/!= NULL"?
> There are two ways:
>
> - the kernel assumes i_op (and similar) is always non-NULL
>   => then we can remove a lot of checks, like the first example above
>
> - the kernel does not assume...
>   => then we need some extra checks, like in the second example above

And a third:

- in some places it's safe to assume non-NULL, but not always
  => then we need to check only the unsafe places

-- 
Måns Rullgård
mru@xxxxxxxxxxxxx

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