From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-dy1-f201.google.com (mail-dy1-f201.google.com [74.125.82.201]) (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 219D919D065 for ; Fri, 1 May 2026 01:19:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=74.125.82.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777598378; cv=none; b=vGEabxfGJ8AzZBk2amXCwBvZBRZMMWht8Y1NMuz0ljLL7GmW4bZspTaci6/OxpO6iOJ68YY6FsLAjfuOebeF8lBti4q0vdyduAOIReW7XcaHYtsKHnUp4O+MbtFe81HE0iifFG8hZtaP1FeBfrlWAwUSO5Lp7Ieu3gJUPyjvYtI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777598378; c=relaxed/simple; bh=IjjQsgkkjACz5DQCM/CJUHDbtQvVrxf2QYzMnKJCAjM=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=i53xLSHEGmCgwvglyrKXClkstz7TubUykUlvzcGAOByg1zMfkp6XZ/3loVYjld73YqFd/8nppjqFQ22nwX77P/iljL5ku9w8mkolrqhiX3lfwK5gNgV980u18xOXtllmWBxIEb8ANLMdefcZpKItEzDGKr3jDg/YrIi2Pp4J7vU= 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=wjOSum3l; arc=none smtp.client-ip=74.125.82.201 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="wjOSum3l" Received: by mail-dy1-f201.google.com with SMTP id 5a478bee46e88-2da19227bc1so6817806eec.1 for ; Thu, 30 Apr 2026 18:19:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1777598376; x=1778203176; darn=vger.kernel.org; h=cc:to:from:subject:message-id:mime-version:date:from:to:cc:subject :date:message-id:reply-to; bh=JxBa4eZL8AzEIKHbrJYGdhnLoHOErJvUxGit6YEswu4=; b=wjOSum3lhDVz8Xnw8EKk6tiYod1lUt7KBs+mSeO2sX+6ysYBBVCL8+wfM7K+abpVZV a31dFXVCJrACsu1qupv+gXRNQPm58jq7NEj8qBPQ5FXAuKssAFt+Ker68XpzNzGewq4/ 0lEfIcwNPa1hQ/+FkgOOjYcTJTGaZvOLABPc8taIWkkDharjG0NVRZfxsS03sQ+kesqK duHPJCOP31zdL175uymLBp8vwN7v6nUvVIyn/IgI8MxxwGOxOiytokANpTcZoB91HHTa WTSPKQknVqbF0EPm/zJ9A7/amqztDY4/5Mt97yydxTYjFJNqxRWTpjKY8iclJZ5yCaJh WKrQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1777598376; x=1778203176; h=cc:to:from:subject:message-id:mime-version:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=JxBa4eZL8AzEIKHbrJYGdhnLoHOErJvUxGit6YEswu4=; b=SsWwnw2i+BLAkecLKcOEawGXRdfHfMespC0D2yUuj62x7hZwcTSL9mB3BI/TlmgDl9 aaLcLjOhaEw+CmT13BC4NHBiajY3F547jbj+CcFSBgQRRRn0NsJ9RNJltVoLYjfJltwN 5GU2vJkrSuCBjqcx4DC0Gg0NUWFmCBH55qxqbFVVVMj7Zoepru7XjYDEUl5kHj4jQ5aK FB91PZrjm5CTtp0kmbPd3dkcUVKYMnoMdrM47ZERawlI83Vg61d7kigl+v4kvLJxvjK2 XX3ZQuhdcfBJlAuaDfFrGilM3YvKXvoS+UllZ1rOu0U1i0xbBvREmh4kE9Gf8QLr9OWt 7/hw== X-Forwarded-Encrypted: i=1; AFNElJ94Lyjx+G9DxreN7xNIduEVBIFL6kxgh08SA938Nz/URZAZePhYVxQQZOUd0tAimLUlwHTrQY6tJUussNE=@vger.kernel.org X-Gm-Message-State: AOJu0YyTWVSId8zTNlEUN0/DD4E6xn87Jl8dZwadVjLbmmwAJJEvzebO 3iU7O/eH4QjIj8nnxt1q+JahvHb1KagNKUFc6P3nDybrUl+J5zoKMNS6yCrZ6BfTP9Ynpl9WY5W VpjILGQ== X-Received: from dlbqs4.prod.google.com ([2002:a05:7023:d04:b0:12c:8bfc:84e3]) (user=fmayle job=prod-delivery.src-stubby-dispatcher) by 2002:a05:7022:2510:b0:11b:f056:a19b with SMTP id a92af1059eb24-12deac72761mr3014031c88.18.1777598376170; Thu, 30 Apr 2026 18:19:36 -0700 (PDT) Date: Thu, 30 Apr 2026 18:19:07 -0700 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 2.54.0.545.g6539524ca2-goog Message-ID: <20260501011908.3630802-1-fmayle@google.com> Subject: [PATCH 1/1] mm/readahead: simplify page_cache_ra_unbounded loop counter reset From: Frederick Mayle To: Matthew Wilcox Cc: android-mm@google.com, kernel-team@android.com, Frederick Mayle , 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 7b05082c89ea..b44f13ce5935 100644 --- a/mm/readahead.c +++ b/mm/readahead.c @@ -270,7 +270,7 @@ 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; } @@ -286,7 +286,7 @@ 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) base-commit: 88ca94c8849696985b1b70ebec4b01c4b58cafdd -- 2.54.0.545.g6539524ca2-goog