From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 662D4361952 for ; Mon, 31 Aug 2026 23:22:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788218572; cv=none; b=g2sCJLLvYY+aj+t9zgpyvIZtTGNB0e82F15jotLIG7VdgME72BQexyzrkAaiYw53JAAauPGcRgOPgP3MGp70ekNDBX0pM3QAj0MceHvLtQKPuqZeKVOZPLGwCmDq1R6y2gv1JYeWI7TSkkiZNLF9LFZ3sWG0xVlLe5FWT25JlPI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788218572; c=relaxed/simple; bh=kq1XWTxBrM/pSLTFGGQ4NqX577GZds5EsJ55vjAFX1k=; h=Message-ID:Date:MIME-Version:Cc:Subject:To:References:From: In-Reply-To:Content-Type; b=VRsFkORpEZ+MOfvj/sbaZ3z2xtoGqyRbs8KLirAXRb6opR2qiF8IuTO7lbwufnJWuhTUBOP/eZfMSFNR7pzqAjhDQByvgvq+vYMrEaSBILS4/pT4yd++3ak+ajVWx6wcIYfed4WErZ4cqJlyP+1DujB4Dt8c8xX4jVQUEPTZcNw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=DlrcnXPj; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="DlrcnXPj" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E16721F000E9; Mon, 31 Aug 2026 23:22:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788218571; bh=b0crU32oQYq0He/VQq4cZn+2RrawFTTcSZI7lulAOgw=; h=Date:Cc:Subject:To:References:From:In-Reply-To; b=DlrcnXPjxBRgnRKdrAXyXDxZT99KhqASelhOnznvAClT5n2WSFgOnbGtjc585Zxs+ hljNLydLacoDEZjONP+MPd27sZsYF0SNxV3OcJhexqhzgWRpjMJaMqvuy4b71Lt86U g3+YX98mElq/o0YYM/ao6bRwfgdUnsudopbZVRsrGURONa3K/WfMV7ztLOe/27dHND Ot+tu66uRyFj3+yg0srgf0cTlDy/gIoWQ1CICSBChWss+iscObJB+Qu3UCEZGf/++p S6cIr4T6L8sQ+sWj3W3QiTAhKowN73rTSmyGkTVgZbauKW5JFAs5WvbJQGQX9qkqu0 w1x51S8mj0lpQ== Message-ID: <9134210e-8ce6-4b74-bc25-af024aabeb75@kernel.org> Date: Tue, 1 Sep 2026 07:22:46 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Cc: chao@kernel.org, jaegeuk@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/5] f2fs: avoid underflow when counting free NIDs To: Xinping Zhang , linux-f2fs-devel@lists.sourceforge.net References: Content-Language: en-US From: Chao Yu In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Kelvin, This patch was wrapped, please resend it as well. On 8/27/26 05:39, Xinping Zhang wrote: > __count_free_nids() subtracts the retention threshold before checking > whether the cached count exceeds it. The operands are unsigned, so a > smaller cache wraps before the result is assigned to long. > > The PAGE_SIZE-derived threshold happens to make this an unsigned long > subtraction, whose wrapped result becomes negative when converted to > long by supported toolchains. Do not rely on operand width or > unsigned-to-signed conversion. Compare values before subtracting. > > Signed-off-by: Kelvin Zhang > --- > fs/f2fs/shrinker.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/fs/f2fs/shrinker.c b/fs/f2fs/shrinker.c > index 4f6bf5926de4..1fd0ee4f89a9 100644 > --- a/fs/f2fs/shrinker.c > +++ b/fs/f2fs/shrinker.c > @@ -23,9 +23,10 @@ static unsigned long __count_nat_entries(struct > f2fs_sb_info *sbi) > > static unsigned long __count_free_nids(struct f2fs_sb_info *sbi) > { > - long count = NM_I(sbi)->nid_cnt[FREE_NID] - MAX_FREE_NIDS; > + unsigned long count = NM_I(sbi)->nid_cnt[FREE_NID]; > + unsigned long max = MAX_FREE_NIDS; > > - return count > 0 ? count : 0; > + return count > max ? count - max : 0; > } > > static unsigned long __count_extent_cache(struct f2fs_sb_info *sbi,