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Date: Mon, 19 Feb 2024 09:11:06 +0100
From: Oscar Salvador <osalvador@suse.de>
To: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Byungchul Park <byungchul@sk.com>, akpm@linux-foundation.org,
	ying.huang@intel.com, hannes@cmpxchg.org,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	kernel_team@skhynix.com, stable@vger.kernel.org
Subject: Re: [PATCH] mm/vmscan: Fix a bug calling wakeup_kswapd() with a
 wrong zone index
Message-ID: <ZdMNGvUOWnNn9zDh@localhost.localdomain>
References: <20240216111502.79759-1-byungchul@sk.com>
 <517e58d4-7537-4d9f-8893-0130c65c3fdb@linux.alibaba.com>
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In-Reply-To: <517e58d4-7537-4d9f-8893-0130c65c3fdb@linux.alibaba.com>

On Mon, Feb 19, 2024 at 02:25:11PM +0800, Baolin Wang wrote:
> This means that there is no memory on the target node？ if so, we can add a
> check at the beginning to avoid calling unnecessary
> migrate_misplaced_folio().
> 
> diff --git a/mm/memory.c b/mm/memory.c
> index e95503d7544e..a64a1aac463f 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -5182,7 +5182,7 @@ static vm_fault_t do_numa_page(struct vm_fault *vmf)
>         else
>                 last_cpupid = folio_last_cpupid(folio);
>         target_nid = numa_migrate_prep(folio, vma, vmf->address, nid,
> &flags);
> -       if (target_nid == NUMA_NO_NODE) {
> +       if (target_nid == NUMA_NO_NODE || !node_state(target_nid, N_MEMORY))
> {
>                 folio_put(folio);
>                 goto out_map;
>         }
> 
> (similar changes for do_huge_pmd_numa_page())

With the check in place from [1], numa_migrate_prep() will also return
NUMA_NO_NODE, so no need for this one here.

And I did not check, but I assume that do_huge_pmd_numa_page() also ends
up calling numa_migrate_prep().

[1] https://lore.kernel.org/lkml/20240219041920.1183-1-byungchul@sk.com/
 

-- 
Oscar Salvador
SUSE Labs