From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.15]) (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 B2B06140389 for ; Tue, 28 May 2024 22:37:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.175.65.15 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1716935878; cv=none; b=pCUErVGcqsGAWkJxn6j2QWMEjvYld00bNTwYk1GJ4lLxxhfZ0HNbky2fT0piYCz1wmCj7PRI9sL2Fx1ZeKZKe03bYm6oVagOlsdiWGfIBxF/+Gu2WiEh3XIj8LXoje/wTjeQhWx5o8iSFYF7sy5hvmcCFq8PuB9mZfJrRM+cR9g= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1716935878; c=relaxed/simple; bh=h0oJbZGASlF6DeFjral+nNflNNppptQROKeRJzlCay0=; h=From:To:Subject:Date:Message-ID:MIME-Version:Content-Type; b=omMuJFZsEbHVrbqUJfAFBarPm44pp53cPGRFGY/OW+xptdWH+WPhy0yz0hHQ4DgamZ9JVKc2i9M3c7DAvVzveQEuEO/Clf28U4NLA971/2Q0+ZtgbJaGB3/GDd71yuWzEwULuDGu0bjOEHwslqvmFb71D+JXlOpe9hS9febEhXw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com; spf=pass smtp.mailfrom=intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=KYhmHs1s; arc=none smtp.client-ip=198.175.65.15 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="KYhmHs1s" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1716935876; x=1748471876; h=from:to:subject:date:message-id:mime-version; bh=h0oJbZGASlF6DeFjral+nNflNNppptQROKeRJzlCay0=; b=KYhmHs1sWbtMUtgwmKtN5xJrimHtoJRYFRCuNl70QG2+/2TBppaRL78z sH3Ui9G4Hruw6SQ9w1079EoxSGDxnkEmhSbp0e2H7oCoaRuAB7ANaKAEa 5rq6VZnUKjRCsu1S32mwASPhT1bEFHHzwe065NLMCsnFFpPpKP08rcSjw y5yOZldjYvczDnX7BnpIgFVjyGJIUt1TiG10QYkpojlfHws+wX/+KrUn7 OsZ2FkutZAYgAGOD2WEBmJSxbv9/sDbmqBA+peWyabnEYLUdxiRdXuORe 2CX9l9o1q31tYjBkWX23Y8eneXMyT1UAfKy4FpVHuf+hLR7/zBvDA0Nqp Q==; X-CSE-ConnectionGUID: XbYJbR+dSDOQeM4Vy4EVTw== X-CSE-MsgGUID: HyWUdv2bSdOY0gKhY1rreg== X-IronPort-AV: E=McAfee;i="6600,9927,11085"; a="17102902" X-IronPort-AV: E=Sophos;i="6.08,196,1712646000"; d="p7s'346?scan'346,208,346";a="17102902" Received: from fmviesa002.fm.intel.com ([10.60.135.142]) by orvoesa107.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 28 May 2024 15:37:55 -0700 X-CSE-ConnectionGUID: F5+mdhphSsmwvDryb967ew== X-CSE-MsgGUID: QM7F3jmtQ1ahRtxiSQPyHA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.08,196,1712646000"; d="p7s'346?scan'346,208,346";a="58406760" Received: from tjmaciei-mobl5.ger.corp.intel.com (HELO tjmaciei-mobl5.localnet) ([10.125.110.251]) by fmviesa002-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 28 May 2024 15:37:54 -0700 From: Thiago Macieira To: linux-btrfs@vger.kernel.org Subject: [6.9 behaviour change] subvolume device ID no longer present in /proc/self/mountinfo Date: Tue, 28 May 2024 19:37:45 -0300 Message-ID: <2548140.Uh0CODmnKu@tjmaciei-mobl5> Organization: Intel Corporation Precedence: bulk X-Mailing-List: linux-btrfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: multipart/signed; boundary="nextPart3439063.sfYGdeWWPf"; micalg="sha256"; protocol="application/pkcs7-signature" --nextPart3439063.sfYGdeWWPf Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="utf-8" Re: https://bugreports.qt.io/browse/QTBUG-125721 Summary: the submodule's block device ID is no longer present in /proc/self/mountinfo. Instead, the root device ID is now shown and that does not match what you get from stat(). Qt's QStorageInfo class used to use this matching to detect when a filesystem had been mounted over and were no longer accessible. With the change in kernel behaviour, QStorageInfo always concludes all btrfs subvolumes are mounted over. When you mount a subvolume, the subvolume gets its own device ID: # mount -o loop fs foo # btrfs sub create foo/@ Create subvolume 'foo/@' # btrfs sub create foo/@home Create subvolume 'foo/@home' # mkdir foo/@/home # umount foo # mount -o loop,subvol=/@ fs foo # mount -o loop,subvol=/@home fs foo/home # stat -c %d foo 149 # stat -c %d foo/home/ 94 In 6.8.8: # grep loop0 /proc/self/mountinfo 340 35 0:149 /@ /tmp/foo rw,relatime shared:310 - btrfs /dev/loop0 rw,ssd,discard=async,space_cache=v2,subvolid=256,subvol=/@ 450 340 0:94 /@home /tmp/foo/home rw,relatime shared:1049 - btrfs /dev/loop0 rw,ssd,discard=async,space_cache=v2,subvolid=257,subvol=/@home In 6.9.1: $ stat -c %d foo foo/home; grep loop0 /proc/self/mountinfo 153 154 486 58 0:151 /@ /tmp/foo rw,relatime shared:445 - btrfs /dev/loop0 rw,ssd,discard=async,space_cache=v2,subvolid=256,subvol=/@ 496 486 0:151 /@home /tmp/foo/home rw,relatime shared:455 - btrfs /dev/loop0 rw,ssd,discard=async,space_cache=v2,subvolid=257,subvol=/@home Note that how device 151 is not the same as reported by stat(). I need to know if this behaviour is expected and will remain, or if it will be fixed, or alternatively if it is a configuration problem somewhere. If it is expected, I will need to find a workaround to solving my problem. Thank you in advance, best regards, -- Thiago Macieira - thiago.macieira (AT) intel.com Principal Engineer - Intel DCAI Fleet Engineering and Quality --nextPart3439063.sfYGdeWWPf Content-Type: application/pkcs7-signature; name="smime.p7s" Content-Disposition: attachment; filename="smime.p7s" Content-Transfer-Encoding: base64 MIIUHAYJKoZIhvcNAQcCoIIUDTCCFAkCAQExDzANBglghkgBZQMEAgEFADALBgkqhkiG9w0BBwGg ghFlMIIFgTCCBGmgAwIBAgIQOXJEOvkit1HX02wQ3TE1lTANBgkqhkiG9w0BAQwFADB7MQswCQYD VQQGEwJHQjEbMBkGA1UECAwSR3JlYXRlciBNYW5jaGVzdGVyMRAwDgYDVQQHDAdTYWxmb3JkMRow GAYDVQQKDBFDb21vZG8gQ0EgTGltaXRlZDEhMB8GA1UEAwwYQUFBIENlcnRpZmljYXRlIFNlcnZp Y2VzMB4XDTE5MDMxMjAwMDAwMFoXDTI4MTIzMTIzNTk1OVowgYgxCzAJBgNVBAYTAlVTMRMwEQYD VQQIEwpOZXcgSmVyc2V5MRQwEgYDVQQHEwtKZXJzZXkgQ2l0eTEeMBwGA1UEChMVVGhlIFVTRVJU UlVTVCBOZXR3b3JrMS4wLAYDVQQDEyVVU0VSVHJ1c3QgUlNBIENlcnRpZmljYXRpb24gQXV0aG9y aXR5MIICIjANBgkqhkiG9w0BAQEFAAOCAg8AMIICCgKCAgEAgBJlFzYOw9sIs9CsVw127c0n00yt 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