From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pg1-f177.google.com (mail-pg1-f177.google.com [209.85.215.177]) (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 50662349AF6 for ; Wed, 1 Jul 2026 14:20:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.215.177 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782915656; cv=none; b=spzTUqXzIRA0EOAz5SW+tKIOPH2D6fodRddBY6KIoGd+zCPkRmv2/m9TAA4M2lYcBY2HvM/XZatB+XEwyg6A53zhdzZP8RDV8iCHgfB1nTepgdKHE5QGttNuQ/EP1QXQZbL2DsNHHk46tXBr3bgCKGFjWSyn0y/L+TagUX55M3A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782915656; c=relaxed/simple; bh=yVLXZoLulwav1PxbuG31HH/kbTVB5XV4YS1ulHW2D/E=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=cznp4miwQ0393lVfckaU5bEJzmWpux80NjnRjNyjuYkpFUuTMQ+5nO4EyrEyuoorMYl/2S8MZ3ntmzqGd/B0vNd9wQDRE1ef3Tflmvb863sc/lDhqdQxBMR6yRNorsVwsJ1qM4ZNvm+r/9yDgl246B6wsa8nhGmHMta8GKh7p2Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=Tw1dl6WR; arc=none smtp.client-ip=209.85.215.177 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Tw1dl6WR" Received: by mail-pg1-f177.google.com with SMTP id 41be03b00d2f7-c9cf07d2df6so223226a12.2 for ; Wed, 01 Jul 2026 07:20:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1782915654; x=1783520454; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=eEE2GOdXPVl+8rgmSuNgRoIW5wbGqI/6NyjVQmxBuik=; b=Tw1dl6WRUjapKRCE2sRRZszJnUAv/6IxVEJHW2GHcvQJwPP0oXwFIUYv9BVCiYNC9b YkdJ2Fnyi8KFKJGOcLp/S5JVeguAfaIjP9oyOBZcXJrVrAtwIWi2z+Z0OnbVKXDp/4C/ c3Acuor10rm3grBRfPUCplMaKO1+MCjTrWpFE4cfs/VFIiT1oxfwI2stamuQkqvYLg5P cztDcWcvzJpJ489+gXcWyRmGbShyi2BdzLtHTTwHw+LNyQlMJ58fVy5AMM5mkhWZTFhh uMuqAyCWQfd2bQfMY+FO0OtAOypDoD++izKKVPtMuwG51qp19CZZuRBD55gvUQTV3h8x Yw2Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1782915654; x=1783520454; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to; bh=eEE2GOdXPVl+8rgmSuNgRoIW5wbGqI/6NyjVQmxBuik=; b=InAYm8bZCZ82OIs00iAoZs1sAACamw6MtbXJLfxMvSrBa7rx/oBtkc5XWuZ+F9LyBp 77DXHaWniZ26qptTgYjbWQk3n0AkRIaSTFYI3PPw99CY3zPHRTM78BDszW8327oU5LUE jzTzZRCj6lBouaiXCSNGJHjpj0Ijb/l1TB0WDQ3V4V39JLnw0fQSgYTgVlXxs16AzQJH QmPs9OEBgV0e2kgeVu0Z4jkJYLOOJaXwckV4Z6GUS6d2b7u3eDXMKcRxZ64NIdnJgAyM k1H3TC45mr7ppSlxPGB4MWug11b5AygZLVYq1BIKeS/I1zk1sHx+0klzMzTeXXyaHhVb wvZQ== X-Gm-Message-State: AOJu0YyR4YrnwhEQNSYuGHweFrwNUKrqO+m5uwhQqIGYgUC+VEHPY3Xy oMA6onIlNkhaS1W/E41CQ/yyYoI6t0grJbD9d8sMRN4kgL7e9JEBplI8BOKHdaWPcMQ= X-Gm-Gg: AfdE7cl2GrWknLE/4ceUOnMxpRENwd+l9zrl9v7pl/Lth7r38h73Ge9+o3OUTtKZDaX cYIad7M4HUKyJGDKKOwG/wSGqgn0acFJvuMacg4pnm6kK6UJI1JhYjwhwtjQN25JwgL9ZqnMxMn 9NrkwBI008HgCx7AgLg6D4CF3bp2VCb3P1GbVJ9Uz3SP7bS7/EGUklNnpMF8lveCx0xF5uD8XW/ zX0KB8xQANjMRtuCX6Oy1jCJ1gpV+cTTZPm546G+YuBFl0S7WXaHLi97y3iODWfnK5VgtnQDGa2 t6H8UjCdix77OjEPcjr1wJIvzaKQT+nWv5Bqs6nuHM+7mdjkMmFPOPr1708XLPe9BbNaIvl44lO cZbuaboW2ji3XlJy6Dnkf2G4pT3WToo+T9vrjHGfKGoyXibTyXoqeY3GT/bKhDwnjwgCmxvpt+t LQ4lnC6j/jnovQDms9CHN8C7hPp7cohTIz9J2XumvZlNg= X-Received: by 2002:a05:6a21:4688:b0:3b4:7eb0:47a1 with SMTP id adf61e73a8af0-3bfed2721b3mr2135991637.19.1782915654529; Wed, 01 Jul 2026 07:20:54 -0700 (PDT) Received: from DESKTOP-DK6PUT8.localdomain ([124.70.231.46]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-c9e32ef8e49sm383894a12.19.2026.07.01.07.20.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 01 Jul 2026 07:20:54 -0700 (PDT) From: yizhang089@gmail.com To: linux-ext4@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, tytso@mit.edu, adilger.kernel@dilger.ca, libaokun@linux.alibaba.com, jack@suse.cz, ojaswin@linux.ibm.com, ritesh.list@gmail.com, yi.zhang@huawei.com, yi.zhang@huaweicloud.com, yizhang089@gmail.com, chengzhihao1@huawei.com, yangerkun@huawei.com Subject: [PATCH 2/6] ext4: clarify return semantics of ext4_load_tail_bh() Date: Wed, 1 Jul 2026 22:20:05 +0800 Message-ID: <20260701142009.1510104-3-yizhang089@gmail.com> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260701142009.1510104-1-yizhang089@gmail.com> References: <20260701142009.1510104-1-yizhang089@gmail.com> Precedence: bulk X-Mailing-List: linux-ext4@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Zhang Yi ext4_load_tail_bh() returns NULL for both holes and clean unwritten buffers, but the conditions that lead to this are not obvious from the code alone. Document this behavior to clarify the return value, so that readers do not mistakenly assume that only holes result in a NULL return. Also update the inline comment following the ext4_get_block() call to reflect this: both holes and clean unwritten buffers fall through to the "nothing to do" path. Signed-off-by: Zhang Yi --- fs/ext4/inode.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index c2c2d6ac7f3d..0b31fa873743 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -4026,6 +4026,10 @@ void ext4_set_aops(struct inode *inode) * because it might have data in pagecache (eg, if called from ext4_zero_range, * ext4_punch_hole, etc) which needs to be properly zeroed out. Otherwise a * racing writeback can come later and flush the stale pagecache to disk. + * + * Return the loaded bh if it actually needs zeroing - in written, dirty + * unwritten, or delalloc state. Return NULL if it's clean (i.e., a hole or + * a clean unwritten block). */ static struct buffer_head *ext4_load_tail_bh(struct inode *inode, loff_t from) { @@ -4065,7 +4069,7 @@ static struct buffer_head *ext4_load_tail_bh(struct inode *inode, loff_t from) if (!buffer_mapped(bh)) { BUFFER_TRACE(bh, "unmapped"); ext4_get_block(inode, iblock, bh, 0); - /* unmapped? It's a hole - nothing to do */ + /* It's a hole or a clean unwritten block - nothing to do */ if (!buffer_mapped(bh)) { BUFFER_TRACE(bh, "still unmapped"); goto unlock; -- 2.53.0