linux-kernel - Re: [PATCH 5/5] staging: lustre: osc_page.c: Use list_for_each_entry

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Message-ID: <CALrZqyOpdt0weNy8qWb2CKLO_0_rd77rLy5sbnyQN83A5dJAtQ@mail.gmail.com>
Date:   Tue, 7 Mar 2017 00:43:39 +0530
From:   SIMRAN SINGHAL <singhalsimran0@...il.com>
To:     James Simmons <jsimmons@...radead.org>
Cc:     oleg.drokin@...el.com, andreas.dilger@...el.com,
        Greg KH <gregkh@...uxfoundation.org>,
        lustre-devel@...ts.lustre.org, devel@...verdev.osuosl.org,
        linux-kernel@...r.kernel.org, outreachy-kernel@...glegroups.com
Subject: Re: [PATCH 5/5] staging: lustre: osc_page.c: Use list_for_each_entry_safe

On Mon, Mar 6, 2017 at 8:50 PM, James Simmons <jsimmons@...radead.org> wrote:
>
>> Doubly linked lists which are  iterated  using list_empty
>> and list_entry macros have been replaced with list_for_each_entry_safe
>> macro.
>> This makes the iteration simpler and more readable.
>>
>> This patch replaces the while loop containing list_empty and list_entry
>> with list_for_each_entry_safe.
>>
>> This was done with Coccinelle.
>>
>> @@
>> expression E1;
>> identifier I1, I2;
>> type T;
>> iterator name list_for_each_entry_safe;
>> @@
>>
>> T *I1;
>> + T *tmp;
>> ...
>> - while (list_empty(&E1) == 0)
>> + list_for_each_entry_safe (I1, tmp, &E1, I2)
>> {
>> ...when != T *I1;
>> - I1 = list_entry(E1.next, T, I2);
>> ...
>> }
>>
>> Signed-off-by: simran singhal <singhalsimran0@...il.com>
>
> NAK!!!!!!
>
> This change was reverted in commit
>
> cd15dd6ef4ea11df87f717b8b1b83aaa738ec8af
>
> Doing these while (list_empty(..)) to list_for_entry...
> are not simple changes and have broken things in lustre
> before. Unless you really understand the state machine of
> the lustre code I don't recommend these kinds of change
> for lustre.
>

Is this for this particular patch or for all the patches of this patch-series.

>> ---
>>  drivers/staging/lustre/lustre/osc/osc_page.c | 11 ++++-------
>>  1 file changed, 4 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/staging/lustre/lustre/osc/osc_page.c b/drivers/staging/lustre/lustre/osc/osc_page.c
>> index ed8a0dc..e8b974f 100644
>> --- a/drivers/staging/lustre/lustre/osc/osc_page.c
>> +++ b/drivers/staging/lustre/lustre/osc/osc_page.c
>> @@ -542,6 +542,7 @@ long osc_lru_shrink(const struct lu_env *env, struct client_obd *cli,
>>       struct cl_object *clobj = NULL;
>>       struct cl_page **pvec;
>>       struct osc_page *opg;
>> +     struct osc_page *tmp;
>>       int maxscan = 0;
>>       long count = 0;
>>       int index = 0;
>> @@ -572,7 +573,7 @@ long osc_lru_shrink(const struct lu_env *env, struct client_obd *cli,
>>       if (force)
>>               cli->cl_lru_reclaim++;
>>       maxscan = min(target << 1, atomic_long_read(&cli->cl_lru_in_list));
>> -     while (!list_empty(&cli->cl_lru_list)) {
>> +     list_for_each_entry_safe(opg, tmp, &cli->cl_lru_list, ops_lru) {
>>               struct cl_page *page;
>>               bool will_free = false;
>>
>> @@ -582,8 +583,6 @@ long osc_lru_shrink(const struct lu_env *env, struct client_obd *cli,
>>               if (--maxscan < 0)
>>                       break;
>>
>> -             opg = list_entry(cli->cl_lru_list.next, struct osc_page,
>> -                              ops_lru);
>>               page = opg->ops_cl.cpl_page;
>>               if (lru_page_busy(cli, page)) {
>>                       list_move_tail(&opg->ops_lru, &cli->cl_lru_list);
>> @@ -1043,6 +1042,7 @@ unsigned long osc_cache_shrink_scan(struct shrinker *sk,
>>  {
>>       struct client_obd *stop_anchor = NULL;
>>       struct client_obd *cli;
>> +     struct client_obd *tmp;
>>       struct lu_env *env;
>>       long shrank = 0;
>>       u16 refcheck;
>> @@ -1059,10 +1059,7 @@ unsigned long osc_cache_shrink_scan(struct shrinker *sk,
>>               return SHRINK_STOP;
>>
>>       spin_lock(&osc_shrink_lock);
>> -     while (!list_empty(&osc_shrink_list)) {
>> -             cli = list_entry(osc_shrink_list.next, struct client_obd,
>> -                              cl_shrink_list);
>> -
>> +     list_for_each_entry_safe(cli, tmp, &osc_shrink_list, cl_shrink_list) {
>>               if (!stop_anchor)
>>                       stop_anchor = cli;
>>               else if (cli == stop_anchor)
>> --
>> 2.7.4
>>
>>