From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-f201.google.com (mail-pf1-f201.google.com [209.85.210.201]) (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 E01723C455F for ; Tue, 12 May 2026 20:32:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778617955; cv=none; b=On4BydEDHon0eo1by94zYuBVfdb8doHr241NWUjSsIIZ33D2GX1FGTMoGaXw1KG/x3MILoTG694XbmPPiWKd6MUlpsups3kXrNNPWSNuHiBEYkrNU4Y7yX98C/dM7U5QDJSZdfkoTh/oY4Uy1ylMwyPQgS3SmyoZF6QMbmS0T74= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778617955; c=relaxed/simple; bh=+8jlEft9WNgvjqTEBfN6erytdcvw5sxxN4Zw4GFtOJo=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: Cc:Content-Type; b=dn9fJO47NbH/oLa3Dw7koeby1uZah3kL+souau5mvGQNo5uKtZUgOVOVI6q0FEYPcyAs2LaM7LiIfjNKTt+atKFfvYdkeOQ5tpCX0LKryEs1bglYFxMFcVlmbx1sJgv8I03+BGnOoR+bepN5LQY4GTggjN0gIlyathCkLoMEXvc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--fmayle.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=ilBtKnwb; arc=none smtp.client-ip=209.85.210.201 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--fmayle.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="ilBtKnwb" Received: by mail-pf1-f201.google.com with SMTP id d2e1a72fcca58-82fa7c6699fso7607820b3a.1 for ; Tue, 12 May 2026 13:32:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1778617953; x=1779222753; darn=vger.kernel.org; h=cc:from:subject:message-id:references:mime-version:in-reply-to:date :from:to:cc:subject:date:message-id:reply-to; bh=Q6bLlWzsZHxTKwI8h2tfKnH8AsKS+KM39iZ5XG/RwLQ=; b=ilBtKnwbb70SE2XSDWEkVSFrLqlAbZb3i++/7g9LaboTX5vj11ODtjuTSMbtVfZ2yI c4t/vrPLLfdaOj79qGZTCTgU6J44NuaKC+ScUjYRA9SLH2Bx1Q2838p5tAfCUxgRHiYr dtgOPWhT8AMUIhuFNq4BiWUu1YG//0MXHoD7a6EAh34r+uSXuBElB4L42LggBEdcWitL 8VU9hp3NS/EdYFqNHHjOOwny7xTqb/dByoBJS3umTPq5JzF4jsEwf8/FdRZ68583V3b9 JfZ3kKCgEZF5C5SDwhI2dVWqh3cWnbBZF8779Emt6mEFXST6aXvMPrzO78clrcWFVz4H EkMw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1778617953; x=1779222753; h=cc:from:subject:message-id:references:mime-version:in-reply-to:date :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=Q6bLlWzsZHxTKwI8h2tfKnH8AsKS+KM39iZ5XG/RwLQ=; b=AOONRNJIXmo9Z6WZRH/WOWZH1IqQWFF9I53Yi0cljGpH91n3oYeDwojiCbepre2SQk 3FcZyF4+2mUV0mZMF6XtSk5vgkyvnHwWY3vrh/sAdvIpgqQ1XPYFUteOxSIwupIF2aoQ eKbmwe+XZBAfZFTMjeCXohBOfnEPpMyQOx7NhFrnCgCCxH89wEAwBRQHVT3PR5q5LH/y f2jIKXE9uDYAEGkS+2fSub3eulCCZIqB9/DFpjYh0Fyc0vLboeMuod3nrukLoivDfDAG Jb9fmnvqJbdvIPz1iBxwNu/15y1oVLcmthDW9hzNndScNN+l2EoReekc+0ieNKkbtEoo xmMA== X-Forwarded-Encrypted: i=1; AFNElJ9AJMAgiK9F/qURM22m714JJiDR8HTREuxNeeHT/hit6H7HVB8H26tvqEbl/VBXRXk1GSQw0P/IEcjDfR6K@vger.kernel.org X-Gm-Message-State: AOJu0YwxBx2nDyEKlN2AkOQ4CPNVgOez3ztN1UF/TiRhUVllyiwBdqQC wx7XFCUACfzR9zFrlNvyYXn1LdRmN7kez+7r61RkoyGQ7y0GXA7fObIxht8kDUHNuZnHNNt8arH v7mYVVQ== X-Received: from pfbg7.prod.google.com ([2002:a05:6a00:ae07:b0:837:c09c:9cce]) (user=fmayle job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a00:328c:b0:82f:2a78:6302 with SMTP id d2e1a72fcca58-83f042789d4mr222577b3a.26.1778617952888; Tue, 12 May 2026 13:32:32 -0700 (PDT) Date: Tue, 12 May 2026 13:31:36 -0700 In-Reply-To: <20260512203154.754075-1-fmayle@google.com> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260512203154.754075-1-fmayle@google.com> X-Mailer: git-send-email 2.54.0.563.g4f69b47b94-goog Message-ID: <20260512203154.754075-3-fmayle@google.com> Subject: [PATCH 2/2] mm/readahead: simplify page_cache_ra_unbounded loop counter reset From: Frederick Mayle Cc: android-mm@google.com, kernel-team@android.com, Frederick Mayle , "Matthew Wilcox (Oracle)" , Jan Kara , Andrew Morton , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Minor cleanup, no behavior change intended. `read_pages` ensures that `ractl->_nr_pages` is zero before it returns, so the `ractl->_nr_pages` term in these expressions contributes nothing. This seems to have been true since the statements were introduced in commit f615bd5c4725f ("mm/readahead: Handle ractl nr_pages being modified"). The new expression has an intuitive explanation. When filesystems perform readahead, they increment `ractl->_index` by the number of pages processed, so, after `read_pages` returns, `ractl->_index` points to the first page after those already processed. `index` points to the first page considered in the loop. So, `ractl->_index - index` is the number of pages processed by the loop so far. Signed-off-by: Frederick Mayle --- mm/readahead.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/mm/readahead.c b/mm/readahead.c index 23bec5497308..42f2f20633b0 100644 --- a/mm/readahead.c +++ b/mm/readahead.c @@ -281,7 +281,7 @@ void page_cache_ra_unbounded(struct readahead_control *ractl, */ read_pages(ractl); ractl->_index += min_nrpages; - i = ractl->_index + ractl->_nr_pages - index; + i = ractl->_index - index; continue; } @@ -297,7 +297,7 @@ void page_cache_ra_unbounded(struct readahead_control *ractl, break; read_pages(ractl); ractl->_index += min_nrpages; - i = ractl->_index + ractl->_nr_pages - index; + i = ractl->_index - index; continue; } if (i == mark) -- 2.54.0.563.g4f69b47b94-goog