From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-yb1-f202.google.com (mail-yb1-f202.google.com [209.85.219.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 499C142A82 for ; Sat, 3 Aug 2024 05:33:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.219.202 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722663191; cv=none; b=p8/rMytaKPWROpwJbKUYhsosTo0dFWRmRWS8FsFA7w9NBP61P2dlbBo6ydtLCenLoT5xdNnF5fctbj0Gxb8cGcgaqjDLllSBDUgIHrdyuTGYk9hIeECjYcLZW28jOyFAzfkJxSgcRQ/gRY5PA6ykARgSiLcx3EJDbEZtXYyhKYU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722663191; c=relaxed/simple; bh=hvUd3OORrhy9zSUxl2DS9XEmSs8zWXzIOk8rRpBAdt4=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=aZ/dOCT+zrUlCYvnGxZZ3nc3uGLnKMGAkYeCdsAkdaXBIM+RPI5YWjuhh5lIIU6tRBrJ8M3HrEMsMQ1OVXANI2AqZPhxYukEq5wapmDxV6knwAexdXaKjkZfXxmDXZe9BHMBHsWmtJJwVZKjYBfMbudmWWu0Thwnqi+KVPVYkVM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--yosryahmed.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=vUjotTFQ; arc=none smtp.client-ip=209.85.219.202 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--yosryahmed.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="vUjotTFQ" Received: by mail-yb1-f202.google.com with SMTP id 3f1490d57ef6-e0be470f76bso3065375276.3 for ; Fri, 02 Aug 2024 22:33:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1722663189; x=1723267989; darn=vger.kernel.org; h=cc:to:from:subject:message-id:mime-version:date:from:to:cc:subject :date:message-id:reply-to; bh=dVMABDG6zvtzBrluDCQkwCGip5NCjvJGZc7ooD15Ipc=; b=vUjotTFQmXdoFgNjtnrNUgk/90RdJc06r0urhzJpvkRpzleVcQp3lY53gHiLXBa55l FX1NdEiTB5979B1VQad7H2gL2j7A3duhmaCH1WfEbpH0n+cvBhKSD9gqJXR2ecHIoX2C 3FLgVCnWy+PGrjy2gV2/WbhBr0WKq1k53z1jU+DaaAJKbnU8wtXPPGNJJ5mY7W6TeHSa zJeH8WUPKvOXWWOcIO8847cVxS7SNPNgRgSY0RiGSDshb90QYnTMF3idmlpfrrRw3MXv fE7Enm0UiUPA4zArNghcsuWPN+EZF0O/9AUkBHDVhzbclNRVMMBVmjV+QaXaZbkmYKxn +HWw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1722663189; x=1723267989; h=cc:to:from:subject:message-id:mime-version:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=dVMABDG6zvtzBrluDCQkwCGip5NCjvJGZc7ooD15Ipc=; b=eDGIX4PaPBhr4IqHHKWOamZyEGNKCt+pvp+Kkg6pCrYUk4H7MVbxdb3xHnrTrciEOX XTUwf0BOYDAWZf3gkGiK7NYpTFneMGCFledKEB9KxaI2DDGEaQBBKQCu6JvK5udfweDE YfHX/lCaAUHmsMJBVWfgzkIo68Jcdk8m3oAuEfYWxNES+IwSMvq9YkPpCOPZ5uiRrHdb Lad55ar8/3VVtweFb8Z7QGBeC9o3XDgKFHQ05Zq83XKvgGnxhr5BMFYOQhbW5yz5geDc T1p7frGnMP1/t8QlPgrCbnfDcc52CCDtRTIE1eoC/an6lpIaTIdP6OUoqUPnj3NQOPoq ZW+w== X-Forwarded-Encrypted: i=1; AJvYcCWXohrM0ONBBL24/XZtWws8fLHKmj5takKhiW+1BWdszYsmVGVG427JriMamk4OWJYlzhQhlEKRcHJ64o7RquIzKHc6sHtoO3kOWgZm X-Gm-Message-State: AOJu0Yx0IlFkwUKmtJZmsCKqvjeAoszGyYlda+WQ/xIfIK4ePSvsFsgI aSrFxmmgqs2okxZ4YlXNhzBpHfjstYMhHQzop2Ow4a9zv6kv5h6OkuqHhyay33jZqlYdQSDiSI3 Atbw7JWmR78cN9MCRxQ== X-Google-Smtp-Source: AGHT+IGiZEPPAQNY2/nwbwVwRsUGjO4TgUlfihhyR0VvwxRkt7mU9aLbAmPrEM8xOeTxVidxnOufplpnPgFzgwEo X-Received: from yosry.c.googlers.com ([fda3:e722:ac3:cc00:20:ed76:c0a8:29b4]) (user=yosryahmed job=sendgmr) by 2002:a05:6902:2313:b0:e05:65b7:32d9 with SMTP id 3f1490d57ef6-e0bde22af67mr16846276.6.1722663189151; Fri, 02 Aug 2024 22:33:09 -0700 (PDT) Date: Sat, 3 Aug 2024 05:33:06 +0000 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Mailer: git-send-email 2.46.0.rc2.264.g509ed76dc8-goog Message-ID: <20240803053306.2685541-1-yosryahmed@google.com> Subject: [PATCH] mm: zswap: make the lock critical section obvious in shrink_worker() From: Yosry Ahmed To: Andrew Morton Cc: Johannes Weiner , Nhat Pham , Chengming Zhou , Takero Funaki , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Yosry Ahmed Content-Type: text/plain; charset="UTF-8" Move the comments and spin_{lock/unlock}() calls around in shrink_worker() to make it obvious the lock is protecting the loop updating zswap_next_shrink. Signed-off-by: Yosry Ahmed --- This is intended to be squashed into "mm: zswap: fix global shrinker memcg iteration". --- mm/zswap.c | 14 ++++++-------- 1 file changed, 6 insertions(+), 8 deletions(-) diff --git a/mm/zswap.c b/mm/zswap.c index babf0abbcc765..df620eacd1d11 100644 --- a/mm/zswap.c +++ b/mm/zswap.c @@ -1364,24 +1364,22 @@ static void shrink_worker(struct work_struct *w) * until the next run of shrink_worker(). */ do { - spin_lock(&zswap_shrink_lock); - /* * Start shrinking from the next memcg after zswap_next_shrink. * When the offline cleaner has already advanced the cursor, * advancing the cursor here overlooks one memcg, but this * should be negligibly rare. + * + * If we get an online memcg, keep the extra reference in case + * the original one obtained by mem_cgroup_iter() is dropped by + * zswap_memcg_offline_cleanup() while we are shrinking the + * memcg. */ + spin_lock(&zswap_shrink_lock); do { memcg = mem_cgroup_iter(NULL, zswap_next_shrink, NULL); zswap_next_shrink = memcg; } while (memcg && !mem_cgroup_tryget_online(memcg)); - /* - * Note that if we got an online memcg, we will keep the extra - * reference in case the original reference obtained by mem_cgroup_iter - * is dropped by the zswap memcg offlining callback, ensuring that the - * memcg is not killed when we are reclaiming. - */ spin_unlock(&zswap_shrink_lock); if (!memcg) { -- 2.46.0.rc2.264.g509ed76dc8-goog