From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 C3F2322DFA4 for ; Thu, 6 Nov 2025 13:48:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762436913; cv=none; b=TcBuPKjaTFK97pF6UTts8XaNxJAXdnfs8KecUe4/NjBQuwCUQ/qrbFN2yvQnMZuKHWka81oJsOzJIOWEdW7e0OLDrNDjV0Jmswy7rogdVaBLnvLqtZQJUQNavPEVUl1lIR9owuFOVegtz2IcjcMcKv4/SUw04u7WojJ3fUGRRso= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762436913; c=relaxed/simple; bh=TuikOT6xWXwFxsuJJ7R+NfK1+n0kSJjfuECC87r7N6E=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=T/evLPpd7bSwZ+d3OZNrXnznBzo1GTWZM+TPaAa9f/F5bFgFAW8iorbT2Wv3LDz596mVkC7iiVftYA8FqPnNqiGXl7LKhi8VF+qwDh0h97pEz8H+r98nOiVWdGMF5vMw2vYALuGAPQ3Vrz+las2D7YLWLgfzQxThUwgtxeasnjU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=XSE13+aG; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="XSE13+aG" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1762436910; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=QoL72t07+fb2NdHff0tfowphC2zMaMnXwcnl9cRu2ps=; b=XSE13+aGql/HHkUA3jt1e6TaY76RrJJckHeAnFZeBbfffmJ8B1kle19a2kY7QUXmVaTW+l dkdeo5QIvQI6hKiG99wTp/N6kkwhU53u+ACFgfvOcE1MY5scsBNoOuOfhC8p+ySUH1cbUa L+pleB2lbE9o/3NyjiHH/tYf84icuqE= Received: from mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-126-eP0SrYTyN2uUEYoqZvSIQg-1; Thu, 06 Nov 2025 08:48:25 -0500 X-MC-Unique: eP0SrYTyN2uUEYoqZvSIQg-1 X-Mimecast-MFC-AGG-ID: eP0SrYTyN2uUEYoqZvSIQg_1762436904 Received: from mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.93]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 9534A180034F; Thu, 6 Nov 2025 13:48:23 +0000 (UTC) Received: from fweimer-oldenburg.csb.redhat.com (unknown [10.45.224.98]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id BEB491800451; Thu, 6 Nov 2025 13:48:20 +0000 (UTC) From: Florian Weimer To: Hans Holmberg Cc: linux-xfs@vger.kernel.org, Carlos Maiolino , Dave Chinner , "Darrick J . Wong" , Christoph Hellwig , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, libc-alpha@sourceware.org Subject: Re: [RFC] xfs: fake fallocate success for always CoW inodes In-Reply-To: <20251106133530.12927-1-hans.holmberg@wdc.com> (Hans Holmberg's message of "Thu, 6 Nov 2025 14:35:30 +0100") References: <20251106133530.12927-1-hans.holmberg@wdc.com> Date: Thu, 06 Nov 2025 14:48:12 +0100 Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Precedence: bulk X-Mailing-List: linux-xfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 * Hans Holmberg: > We don't support preallocations for CoW inodes and we currently fail > with -EOPNOTSUPP, but this causes an issue for users of glibc's > posix_fallocate[1]. If fallocate fails, posix_fallocate falls back on > writing actual data into the range to try to allocate blocks that way. > That does not actually gurantee anything for CoW inodes however as we > write out of place. Why doesn't fallocate trigger the copy instead? Isn't this what the user is requesting? Thanks, Florian