From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mta0.migadu.com (out-146.mta0.migadu.com [91.218.175.146]) (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 89CBB3D6485 for ; Thu, 20 Aug 2026 08:21:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.146 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787214081; cv=none; b=SlVnB7J0zqstKVnX4DQGzQfkC/XYAaWk9a6EXelrxopclmyEPsCfgDDHB2e6jkvErxC2Ln6P5J4JZB2xFC7CMBU5TABvb0E09ZqN1fEOskZ7NQZOYaXM0z8MQpKpaOdo1bxt42p8Q3g4q921/nQWZmluq5ZBG5A2evssseLnGlc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787214081; c=relaxed/simple; bh=d1jsNWuE7ULunmJ8bkSavDLs3vrprYcUarJdoXM2dpU=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=UAv94HzBQM4EbK1LdoKxS27C1iFt09LK2UzzAxuDrDSAT6nEW4v+fT6L3nSFpIC2Ra2BvxHGCJrMQpvbWHerwbTrogu5svKEHEYZ3Xvd4ZS67wT/gf313dj6+SaNqZoMeafnGseiyKeVHh997thNWuMjeI/TZbwNn0jEvvJPRnY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=BY7EAL6W; arc=none smtp.client-ip=91.218.175.146 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="BY7EAL6W" X-Envelope-To: linux-ext4@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=d1jsNWuE7ULunmJ8bkSavDLs3vrprYcUarJdoXM2dpU=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1787214077; v=1; x=1787818877; b=BY7EAL6WGxfDbG4l6MPbp9U5kGh86tE/WaJIDRnuL81KXEd46OGZ4FtHPVJht9GxOw/wwnS3 93sSeyrEEfQLVSiEVvSH4/Mh4b8Ia5Dkwlw6b8+RnDITXYyWbqQwnT+4TcCbikUNewndTI4MOGp TITq7ksssbvPjYOEdQmCu/ZM= X-Envelope-To: linux-ext4@vger.kernel.org Received: from [192.168.8.135] (87.104.0.147) by smtp.migadu.com with ESMTPS id e6c688cadc82bb73; Thu, 20 Aug 2026 08:21:07 +0000 X-Mizu-Trace-ID: e6c688cadc82bb73 X-Migadu-Flow: FLOW_OUT Message-ID: Date: Thu, 20 Aug 2026 10:21:06 +0200 Precedence: bulk X-Mailing-List: linux-ext4@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] man2/fallocate.2: add doc for FALLOC_FL_WRITE_ZEROES To: Zhang Yi , Pankaj Raghav , linux-man@vger.kernel.org, Alejandro Colomar Cc: linux-xfs@vger.kernel.org, "Darrick J . Wong" , linux-ext4@vger.kernel.org, gost.dev@samsung.com, hch@lst.de References: <20260819114022.818734-1-p.raghav@samsung.com> Content-Language: en-US From: Pankaj Raghav In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit > FALLOC_FL_WRITE_ZEROES itself is relatively flexible. It does not > mandate that the filesystem must implement zeroing via unmap write > zeroes. That depends on the specific implementation of each filesystem. > Currently, ext4, xfs, and block devices (bdev) support this operation > through that approach, since writing zeros directly on devices that do > not support unmap zeroes can be very slow and thus of little practical > value. > > Therefore, I would suggest referring to the description in, for > example, fallocate(1): > > https://man7.org/linux/man-pages/man1/fallocate.1.html > > "Zeroing is done within the filesystem. The > filesystem may use a hardware-accelerated zeroing command or may > submit regular writes. The behavior depends on the filesystem design > and the available hardware." > > What do you think? > You are right. It is up to the FSs to implement however it wants. I will use this framing instead. Thanks. >> +This approach means that the specified range will be physically zeroed out >> +on the device (including partial blocks at the either end of the range). >> +.P >> +No other flags may be specified in >> +.I mode >> +in conjunction with >> +.BR FALLOC_FL_WRITE_ZEROES . >> +.P >> +Not all filesystems support >> +.BR FALLOC_FL_WRITE_ZEROES ; >> +if a filesystem doesn't support the operation, an error is returned. >> +The operation is supported only in ext4 (since Linux 6.17). > ^^^^ > ext4 (only for extent-based files) > Sounds good. -- Pankaj