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SubjectRe: [PATCH v2 0/2] gfs2: Stop using rhashtable_walk_peek
On Fri, Mar 30 2018, Herbert Xu wrote:

> On Thu, Mar 29, 2018 at 06:52:34PM +0200, Andreas Gruenbacher wrote:
>>
>> Should rhashtable_walk_peek be kept around even if there are no more
>> users? I have my doubts.
>
> Absolutely. All netlink dumps using rhashtable_walk_next are buggy
> and need to switch over to rhashtable_walk_peek. As otherwise
> the object that triggers the out-of-space condition will be skipped
> upon resumption.

Do we really need a rhashtable_walk_peek() interface?
I imagine that a seqfile ->start function can do:

if (*ppos == 0 && last_pos != 0) {
rhashtable_walk_exit(&iter);
rhashtable_walk_enter(&table, &iter);
last_pos = 0;
}
rhashtable_walk_start(&iter);
if (*ppos == last_pos && iter.p)
return iter.p;
last_pos = *ppos;
return rhashtable_walk_next(&iter)


and the ->next function just does

last_pos = *ppos;
*ppos += 1;
do p = rhashtable_walk_next(&iter); while (IS_ERR(p));
return p;

It might be OK to have a function call instead of expecting people to
use iter.p directly.

static inline void *rhashtable_walk_prev(struct rhashtable_iter *iter)
{
return iter->p;
}

Thoughts?

Thanks,
NeilBrown
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