Re: [PATCH 3/6] gfs2: simplify current_tail() vialist_last_entry_or_null()
From: Oleg Nesterov
Date: Fri Nov 15 2013 - 11:39:22 EST
On 11/15, Jeff Liu wrote:
>
> @@ -441,13 +441,9 @@ static unsigned int current_tail(struct gfs2_sbd *sdp)
>
> spin_lock(&sdp->sd_ail_lock);
>
> - if (list_empty(&sdp->sd_ail1_list)) {
> - tail = sdp->sd_log_head;
> - } else {
> - tr = list_entry(sdp->sd_ail1_list.prev, struct gfs2_trans,
> - tr_list);
> - tail = tr->tr_first;
> - }
> + tr = list_last_entry_or_null(&sdp->sd_ail1_list, struct gfs2_trans,
> + tr_list);
> + tail = tr ? tr->tr_first : sdp->sd_log_head;
>
Personally I agree with Steven. At least in this case
list_last_entry_or_null() doesn't really help to simplify the code.
But probably list_last_entry() makes sense in the "else" branch,
athough this is minor.
Off-topic. Not sure this really makes sense, but I was thinking about
list_get_first(pos, head, member) \
((pos) = list_first_entry(head, typeof(*pos), member))
and list_get_first() last of course. The obvious advantage is that
compared to
tr = list_last_entry(sdp->sd_ail1_list, struct gfs2_trans, tr_list);
above you do not need to type "struct gfs2_trans",
list_get_last(tr, sdp->sd_ail1_list, tr_list);
looks a bit better.
Oleg.
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