2018-08-17 10:10:58

by Mukesh Ojha

[permalink] [raw]
Subject: Query on shrink list

Hi Al Viro,

Is there is reason we have kept data->found++, if the dentry already
there in shrink list ?

static enum d_walk_ret select_collect(
...
        if (dentry->d_flags & DCACHE_SHRINK_LIST) {
                data->found++;
        } else {
  ..

If the dentry is already there on shrink list, does it not mean that
data->found is already non-zero ?
Can't we just go out from here directly?


Regards,
Mukesh



2018-08-17 12:59:32

by Al Viro

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Subject: Re: Query on shrink list

On Fri, Aug 17, 2018 at 03:39:22PM +0530, Mukesh Ojha wrote:
> Hi Al Viro,
>
> Is there is reason we have kept data->found++, if the dentry already there
> in shrink list ?
>
> static enum d_walk_ret select_collect(
> ...
> ??????? if (dentry->d_flags & DCACHE_SHRINK_LIST) {
> ??????????????? data->found++;
> ??????? } else {
> ? ..
>
> If the dentry is already there on shrink list, does it not mean that
> data->found is already non-zero ?

Nope. It can be on *another* shrink list - if two processes are doing
that...

> Can't we just go out from here directly?

2018-08-17 14:39:29

by Mukesh Ojha

[permalink] [raw]
Subject: Re: Query on shrink list



On 8/17/2018 6:28 PM, Al Viro wrote:
> On Fri, Aug 17, 2018 at 03:39:22PM +0530, Mukesh Ojha wrote:
>> Hi Al Viro,
>>
>> Is there is reason we have kept data->found++, if the dentry already there
>> in shrink list ?
>>
>> static enum d_walk_ret select_collect(
>> ...
>>         if (dentry->d_flags & DCACHE_SHRINK_LIST) {
>>                 data->found++;
>>         } else {
>>   ..
>>
>> If the dentry is already there on shrink list, does it not mean that
>> data->found is already non-zero ?
> Nope. It can be on *another* shrink list - if two processes are doing
> that...

Ok, if we go out simply,  letting others to do the job will break
`shrink_dcache_parent()`
and if someone touched that dentry made the refcount > 0 while it is on
shrink list
 then owner will keep on looping in shrink_dentry_list() until refcount
becomes 0 .

Am i making sense here ?

Thanks.
Mukesh

>
>> Can't we just go out from here directly?