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Date:   Sun, 25 Jun 2023 11:34:00 +0200
From:   Greg KH <greg@kroah.com>
To:     =?utf-8?B?5p2O5Z+56ZSLKHdpbmsp?= <lipeifeng@oppo.com>
Cc:     David Hildenbrand <david@redhat.com>,
        "akpm@linux-foundation.org" <akpm@linux-foundation.org>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "surenb@google.com" <surenb@google.com>,
        "gregkh@google.com" <gregkh@google.com>,
        "zhangshiming@opp.com" <zhangshiming@opp.com>,
        =?utf-8?B?6YOt5YGl?= <guojian@oppo.com>
Subject: Re: =?utf-8?B?5Zue5aSN?= =?utf-8?Q?=3A?= [PATCH] mm: vmscan: export
 func:shrink_slab
Message-ID: <2023062554-gecko-cyclist-0c78@gregkh>
References: <20230616092112.387-1-lipeifeng@oppo.com>
 <33eabee3-f6f4-ee0c-d74b-98815a9567c4@redhat.com>
 <TYZPR02MB5595CE108D89A51973CF551AC65CA@TYZPR02MB5595.apcprd02.prod.outlook.com>
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On Tue, Jun 20, 2023 at 03:05:27AM +0000, 李培锋(wink) wrote:
> On 16.06.23 11:21, lipeifeng@oppo.com wrote:
> >> From: lipeifeng <lipeifeng@oppo.com>
> >> 
> >> Some of shrinkers during shrink_slab would enter synchronous-wait due 
> >> to lock or other reasons, which would causes kswapd or direct_reclaim 
> >> to be blocked.
> >> 
> >> This patch export shrink_slab so that it can be called in drivers 
> >> which can shrink memory independently.
> >> 
> >> Signed-off-by: lipeifeng <lipeifeng@oppo.com>
> >> ---
> >>   mm/vmscan.c | 3 ++-
> >>   1 file changed, 2 insertions(+), 1 deletion(-)
> >> 
> >> diff --git a/mm/vmscan.c b/mm/vmscan.c index 
> >> 6d0cd2840cf0..2e54fa52e7ec 100644
> >> --- a/mm/vmscan.c
> >> +++ b/mm/vmscan.c
> >> @@ -1043,7 +1043,7 @@ static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid,
> >>    *
> >>    * Returns the number of reclaimed slab objects.
> >>    */
> >> -static unsigned long shrink_slab(gfp_t gfp_mask, int nid,
> >> +unsigned long shrink_slab(gfp_t gfp_mask, int nid,
> >>   				 struct mem_cgroup *memcg,
> >>   				 int priority)
> >>   {
> >> @@ -1087,6 +1087,7 @@ static unsigned long shrink_slab(gfp_t gfp_mask, int nid,
> >>   	cond_resched();
> >>   	return freed;
> >>   }
> >> +EXPORT_SYMBOL_GPL(shrink_slab);
> >>   
> >>   static unsigned long drop_slab_node(int nid)
> >>   {
> >
> >It feels like something we don't want arbitrary drivers to call.
> >
> >Unrelated to that, this better be sent along with actual driver usage.
> 
> Hi Sir：
> 
> Virtually, we have implemented async shrink_slabd isolated from kswapd and direct_reclaim.
> The goal above it is to avoid the sync-wait in kswapd or direct_reclaim due to some shrinkers.
> 
> But the async shrink_slabd was only applied to mobile products so that I didn't make sure any
> risk in other products. For the above reasons, I wanna merge the patch to export shrink_slab
> and the patch of drivers would be considered to be pushed if I check all the risks.
> 
> Some informal code files of driver are attached for your reference.

You have to submit this as a real series, we can not accept exports for
no in-kernel users (nor would you want us to, as that ends up being an
unmaintainable mess.)

So please resubmit this as a proper patch series, with the user of this
function, and then it can be properly evaluated.  As-is, this can not be
accepted at all.

thanks,

greg k-h