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From: YoungJun Park <youngjun.park@lge.com>
To: kasong@tencent.com
Cc: linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
	David Hildenbrand <david@kernel.org>, Zi Yan <ziy@nvidia.com>,
	Baolin Wang <baolin.wang@linux.alibaba.com>,
	Barry Song <baohua@kernel.org>, Hugh Dickins <hughd@google.com>,
	Chris Li <chrisl@kernel.org>,
	Kemeng Shi <shikemeng@huaweicloud.com>,
	Nhat Pham <nphamcs@gmail.com>, Baoquan He <bhe@redhat.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Chengming Zhou <chengming.zhou@linux.dev>,
	Roman Gushchin <roman.gushchin@linux.dev>,
	Shakeel Butt <shakeel.butt@linux.dev>,
	Muchun Song <muchun.song@linux.dev>,
	Qi Zheng <zhengqi.arch@bytedance.com>,
	linux-kernel@vger.kernel.org, cgroups@vger.kernel.org,
	Yosry Ahmed <yosry@kernel.org>, Lorenzo Stoakes <ljs@kernel.org>,
	Dev Jain <dev.jain@arm.com>, Lance Yang <lance.yang@linux.dev>,
	Michal Hocko <mhocko@suse.com>, Michal Hocko <mhocko@kernel.org>,
	Qi Zheng <qi.zheng@linux.dev>
Subject: Re: [PATCH v2 09/11] mm/memcg, swap: store cgroup id in cluster table directly
Date: Sat, 18 Apr 2026 23:03:22 +0900	[thread overview]
Message-ID: <aeOPKlF4qAdM2oMH@yjaykim-PowerEdge-T330> (raw)
In-Reply-To: <20260417-swap-table-p4-v2-9-17f5d1015428@tencent.com>


> +		if (IS_ENABLED(CONFIG_MEMCG) && !memcg_table) {
> +			swap_table_free(table);
> +			return -ENOMEM;
> +		}

Hi Kairui,

Nit: 
(Just a readability nit. purely my preference, feel free to ignore.)
the checks around swap_memcg_table_alloc() reduce to two
equivalent forms of the same memcg success/failure question:

(!IS_ENABLED(CONFIG_MEMCG) || memcg_table)   /* success */
(IS_ENABLED(CONFIG_MEMCG) && !memcg_table)   /* failure */

A macro for the failure side would let the call sites read as plain
positive/negative:

#define SWAP_MEMCG_TABLE_ALLOC_FAILED(t) \
	(IS_ENABLED(CONFIG_MEMCG) && !(t))

SWAP_MEMCG_TABLE_ALLOC_FAILED(memcg_table)     /* failure */
!SWAP_MEMCG_TABLE_ALLOC_FAILED(memcg_table)    /* success */

Equivalently, the same macro can be expressed by splitting on
CONFIG_MEMCG.

#ifdef CONFIG_MEMCG
#define SWAP_MEMCG_TABLE_ALLOC_FAILED(t)  (!(t))
#else
#define SWAP_MEMCG_TABLE_ALLOC_FAILED(t)  (0)
#endif

What do you think?

Thanks,
Youngjun Park


  reply	other threads:[~2026-04-18 14:03 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-04-16 18:34 [PATCH v2 00/11] mm, swap: swap table phase IV: unify allocation and reduce static metadata Kairui Song via B4 Relay
2026-04-16 18:34 ` [PATCH v2 01/11] mm, swap: simplify swap cache allocation helper Kairui Song via B4 Relay
2026-04-16 18:34 ` [PATCH v2 02/11] mm, swap: move common swap cache operations into standalone helpers Kairui Song via B4 Relay
2026-04-16 18:34 ` [PATCH v2 03/11] mm/huge_memory: move THP gfp limit helper into header Kairui Song via B4 Relay
2026-04-16 18:34 ` [PATCH v2 04/11] mm, swap: add support for stable large allocation in swap cache directly Kairui Song via B4 Relay
2026-04-17  3:19   ` Kairui Song
2026-04-16 18:34 ` [PATCH v2 05/11] mm, swap: unify large folio allocation Kairui Song via B4 Relay
2026-04-16 18:34 ` [PATCH v2 06/11] mm/memcg, swap: tidy up cgroup v1 memsw swap helpers Kairui Song via B4 Relay
2026-04-16 18:34 ` [PATCH v2 07/11] mm, swap: support flexible batch freeing of slots in different memcg Kairui Song via B4 Relay
2026-04-16 18:34 ` [PATCH v2 08/11] mm/swap: delay and unify memcg lookup and charging for swapin Kairui Song via B4 Relay
2026-04-16 18:34 ` [PATCH v2 09/11] mm/memcg, swap: store cgroup id in cluster table directly Kairui Song via B4 Relay
2026-04-18 14:03   ` YoungJun Park [this message]
2026-04-16 18:34 ` [PATCH v2 10/11] mm/memcg: remove no longer used swap cgroup array Kairui Song via B4 Relay
2026-04-16 18:34 ` [PATCH v2 11/11] mm, swap: merge zeromap into swap table Kairui Song via B4 Relay
2026-04-18 12:27   ` YoungJun Park
2026-04-18 13:34     ` Kairui Song

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