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AJvYcCUpUSE0Vs7Qrc6Mouv48OLKpxH5eoBjG0ppW2LONzNBnwDp6iimnHhHLP3OZVSvS122X88aM6tfng==@kvack.org X-Gm-Message-State: AOJu0Yz248aoHHd0RSLUBwV0QWTjGGxX96iCanLX0opOGqgXuHUJtxjb A/HtI2iNpQ+pe5CdvjcEQFFuP5XpW1ivdRXTslRZ0081Y1B1UlK04eylta7ccaUIEXHuQqfTgX+ 4Qd5kQcAhETydOIdxv5Qr9Ea1Pohj3l0= X-Gm-Gg: ASbGncsHRlnLOhlNEL+E0pl4BolXcHAU9UMtWK31kj8jnGJqskpcM6O1GFi4ENTgwjw azde1ranwKmEULf4JVjyoeWj1beGqEm1VqiUGu4XFTOMaU++rGBsdIeZAQWk3iZZF8+V0fKpmZW dp8ehIhoW5B6NwD2NPv+IHQKOr8+czNLsDLozMaJFZzio= X-Google-Smtp-Source: AGHT+IGdF3FSVZD5Fi7wP3dVo0YI2cmNqGZYNAOM3JBWdYgK0ARd5VLl/zUPmWQRkQXA5cuMhwSjnkaS20tEJ9ouZdQ= X-Received: by 2002:a05:651c:40cd:b0:328:1163:e86a with SMTP id 38308e7fff4ca-3281163eac5mr55777271fa.22.1747886118295; Wed, 21 May 2025 20:55:18 -0700 (PDT) MIME-Version: 1.0 References: <20250522122554.12209-1-shikemeng@huaweicloud.com> <20250522122554.12209-2-shikemeng@huaweicloud.com> In-Reply-To: <20250522122554.12209-2-shikemeng@huaweicloud.com> From: Kairui Song Date: Thu, 22 May 2025 11:55:01 +0800 X-Gm-Features: AX0GCFvtYmu3WgITSY2-7KAJSRWbqDXUSJnIAKwATmT-2qsQdK2T3QzMWj7FmTY Message-ID: Subject: Re: [PATCH 1/4] mm: swap: move nr_swap_pages counter decrement from folio_alloc_swap() to swap_range_alloc() To: Kemeng Shi Cc: akpm@linux-foundation.org, bhe@redhat.com, hannes@cmpxchg.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 8BB2C140007 X-Stat-Signature: cixegkkyp8456nnsbf58imbmr17zee5q X-Rspam-User: X-HE-Tag: 1747886120-678707 X-HE-Meta: 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 Fbzwfura D843awke9VPRt7rvMgkrgilEO1uBvz0sSQh2GeFL6CLy2+A9qZGnxqpwKkTea/V9ZkhxRcJXFKFFLMXqkoBmkUFvoam2xCAxjHnVbq8PBjNStcwSQnS2QBeCFYnYHZQbKrjdzrxLSlvWj2xNdKepzYFA2b9G8/6cKMb81YbCAVjHa68WAc3fFfrPGTpnIuuzAxPkx3ucimwcX39wDAVketBkuCfbE6ypN2Vzj+knn42wb1CdrDGBjwKafv1JTX2QTwFh/3dhjHkTJ7fq+sYSBd+tHL+vATpY93OwA5rdi4Ekn70pnWQnNCJYn+Nox3XyNEM52dJb0APh0cMt/+xfVD4+jT+noyTygvFmMmEu6fUNcZqEN6ArRgUdfQcBa7qOIJd9LsSwpOIQMIaHTSDSMDcrVsS12J0kGkGF+ X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, May 22, 2025 at 11:32=E2=80=AFAM Kemeng Shi wrote: > > When folio_alloc_swap() encounters a failure in either > mem_cgroup_try_charge_swap() or add_to_swap_cache(), nr_swap_pages counte= r > is not decremented for allocated entry. However, the following > put_swap_folio() will increase nr_swap_pages counter unpairly and lead to > an imbalance. > > Move nr_swap_pages decrement from folio_alloc_swap() to swap_range_alloc(= ) > to pair the nr_swap_pages counting. > > Fixes: 0ff67f990bd45 ("mm, swap: remove swap slot cache") > Signed-off-by: Kemeng Shi > --- > mm/swapfile.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/swapfile.c b/mm/swapfile.c > index 026090bf3efe..75b69213c2e7 100644 > --- a/mm/swapfile.c > +++ b/mm/swapfile.c > @@ -1115,6 +1115,7 @@ static void swap_range_alloc(struct swap_info_struc= t *si, > if (vm_swap_full()) > schedule_work(&si->reclaim_work); > } > + atomic_long_sub(nr_entries, &nr_swap_pages); > } > > static void swap_range_free(struct swap_info_struct *si, unsigned long o= ffset, > @@ -1313,7 +1314,6 @@ int folio_alloc_swap(struct folio *folio, gfp_t gfp= ) > if (add_to_swap_cache(folio, entry, gfp | __GFP_NOMEMALLOC, NULL)= ) > goto out_free; > > - atomic_long_sub(size, &nr_swap_pages); > return 0; > > out_free: > -- > 2.30.0 Good catch! Moving the counter update to swap_range_alloc makes the logic much easier to follow. Reviewed-by: Kairui Song