From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 2E987158535; Tue, 12 May 2026 08:01:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.133 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778572914; cv=none; b=fO3fddziBjBlSNiPX982wY7dAiWiudlASL0QlTRUT9bFqx6xbT7Uhmfub5WxhFo4eJ8EAF9hIjV0B80DtlQt+CjnSR5wZ2eBqTiYnKCx8F16qwwIwulZHR8zqwiWuNLkSOhIu3oql366qd0IpdCrTYuiU6uZ7iAPLEe0EisChKU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778572914; c=relaxed/simple; bh=9fOF9NG9sNtOShx9C8ACn6+YUbk2PL9B32d5xWt27gk=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=IWntWQGpiGvGyh7UDGd5yaQ3szAO7GQe/CjBCnhQN3IMyUh5Z5p2PhzJnCsXqTE2JgKO/k93oJH7R1TDLmtNK2iXK9+1EUYe5S0ODNE+SIgM0BhdQPpnvkEqRlB1zQs99cTIiUr+TCwgdmQE7H4n9t293OND4Us7EwdH9N/D+Es= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=bombadil.srs.infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=olHmLIxo; arc=none smtp.client-ip=198.137.202.133 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=bombadil.srs.infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="olHmLIxo" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=qjI94m8Qked++riFwWLC/SJ+hyu2Wf6SY3/bFqr0b9U=; b=olHmLIxoWiEyIV6DzqayxxwgCR Z4wV885pWNVvoeQtlDhg39hvikuWzmZy7VjEioUrwWSOG+ZiXztyzRFyhII1H2WZjo3h/uHMiSnaw Ja+15siuFkvFEPLgjZbpSU8rJIT/n/qpaTrnMHd+nMlQs373tFpwp1M0G5dMEN60pE77VHZZafmFn 9g4ZnV0+dknATzi11MxSsttfGhLRKSyXpJdI7NrQ4OLHl53bTwlMWjPsBXP9QPfNv5i3xSKVV4Ghj xg/hWK1TRM3olGsgn5KbMP+o9vuGfTGtm/4H4R2ozPo2drqrifJddxzaUaqJEzDk1rOXWWsqrvAeT J118o6Ww==; Received: from hch by bombadil.infradead.org with local (Exim 4.99.1 #2 (Red Hat Linux)) id 1wMi3r-0000000G16l-0yHr; Tue, 12 May 2026 08:01:51 +0000 Date: Tue, 12 May 2026 01:01:51 -0700 From: Christoph Hellwig To: Arun Rao Balappa Cc: linux-pm@vger.kernel.org, rafael@kernel.org, lenb@kernel.org, pavel@kernel.org, linux-kernel@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH] docs/power: note Btrfs limitation with FIBMAP for swap file offset Message-ID: References: <20260512063713.77200-1-arunraobalappa@gmail.com> Precedence: bulk X-Mailing-List: linux-btrfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260512063713.77200-1-arunraobalappa@gmail.com> X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html On Tue, May 12, 2026 at 12:07:13PM +0530, Arun Rao Balappa wrote: > On Btrfs, the FIBMAP ioctl does not return physical block addresses. On btrfs, and on anything that writes out of place or uses multiple devices for that matter, FIBMAP is not implemented. > Tools such as filefrag therefore cannot determine the correct swap file > offset for use as resume_offset. Document the correct btrfs-progs > command to use instead. All of this is inherently unsafe. File systems and do move file data without notifying users. This document is a really bad idea and should be removed as we should not encourage users to rely on these kinds of hacks.