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 B1C63145323; Fri, 16 May 2025 06:00:17 +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=1747375221; cv=none; b=PbaCnrnC0VNt0zk/JoqUKC3PrPVtzhQoSn5i4N4Ce4/CB3+pf/h3ARC5UFHPWlUPP4TwbLK4jYjDsywQq3VuSQtDKbmSP5rBvhoXqBZ3q8euSXmk6bPiMvNN+Qy1+KeFb/Eg0PDUMISSn9ZY4Amo2EbtUKBzY9hTTBjbgyN4HNE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747375221; c=relaxed/simple; bh=jRcCQqKoajgCHcqKZL2fKVR9zn8kYTEKLbF6ph3kb9s=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=I6VSauzHnOeKJGTAYIz2vtWIYdqQCljtPEXbTDpPa++EQcCriuyhftuk9P6AeeBH0z0n/aBfqaI3aI3GcbtESVyPzWniEr/KXcGcfm4p4C2888BD5sGMVxP9NfeeKrG9xiEApVBzzLoMGZfawytOwarIHCHz5SuFscDWO9swaLU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (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=W6r+kAM3; arc=none smtp.client-ip=198.137.202.133 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (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="W6r+kAM3" 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=tMkAG2SFACdyzL8iUB+Wxh6SJJ+34J1Qx1KU18J0p3Y=; b=W6r+kAM3drfZk7z4FiEyTqXGFI OxPSN+0oTLerhucmtXvIp5AGqSP8Uvx0I9gq2toJ4ceOjhz7qpFE+MLAs9kDey6PorkOLeNK2yDRr tfAGBIBdkiWUF9VAztyncBX/uNpYOgk3gwEsIpOsQo89sQsJiVsVylWGs4IUr/olWnjweBPX8d6JT BzjVdH5QbCgiXTQDu/i/c4uu3668SH3OXLKyQGlNQneOIvT7NwMZj8h6kibCK8ZJa2c1TOMk2yMOX TAqQGT25siJz2NolUgJ0qJZ5kJnI+kzZGGCjh2e7U33i7m+M4wGHeGEL4O5nn7gaFA52T62/R7PZp 7uK8hPdw==; Received: from hch by bombadil.infradead.org with local (Exim 4.98.2 #2 (Red Hat Linux)) id 1uFo7F-00000002Xly-0cgy; Fri, 16 May 2025 06:00:17 +0000 Date: Thu, 15 May 2025 23:00:17 -0700 From: Christoph Hellwig To: Kevin Wolf Cc: Martin Wilck , Christoph Hellwig , Benjamin Marzinski , dm-devel@lists.linux.dev, hreitz@redhat.com, mpatocka@redhat.com, snitzer@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 0/2] dm mpath: Interface for explicit probing of active paths Message-ID: References: <20250429165018.112999-1-kwolf@redhat.com> <47dd225b433b0df585a25084a2e793344eeda239.camel@suse.com> Precedence: bulk X-Mailing-List: linux-kernel@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: X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html On Thu, May 15, 2025 at 12:11:49PM +0200, Kevin Wolf wrote: > If you're talking about SG_IO in dm-mpath, then PRIN/PROUT commands are > actually the one thing that we don't need. libmpathpersist sends the > commands to the individual path devices, so dm-mpath will never see > those. It's mostly about getting the full results on the SCSI level for > normal I/O commands. > > There has actually been a patch series on qemu-devel last year (that I > haven't found the time to review properly yet) that would add explicit > persistent reservation operations to QEMU's block layer that could then > be used with the emulated scsi-hd device. On the backend, it only > implemented it for iscsi, but I suppose we could implement it for > file-posix, too (using the same libmpathpersist code as for > passthrough). If that works, maybe at least some users can move away > from SCSI passthrough. Please call into the kernel PR code instead of hacking up more of this, which will just run into problems again. > The thing that we need to make sure, though, is that the emulated status > we can expose to the guest is actually good enough. That Paolo said that > the problem with reservation conflicts was mostly because -EBADE wasn't > a thing yet gives me some hope that at least this wouldn't be a problem > any more today. And if you need more information we can add that to the kernel PR API.