From mboxrd@z Thu Jan 1 00:00:00 1970 From: Donald Buczek Subject: Re: "Too many levels of symbolic links" Date: Fri, 28 Feb 2014 21:35:25 +0100 Message-ID: <5310F30D.9040407@molgen.mpg.de> References: <1391145206.2486.25.camel@perseus.fritz.box> <52EB7694.20707@molgen.mpg.de> <52EB7B07.2070707@molgen.mpg.de> <530484B7.6030305@molgen.mpg.de> <1392896501.2508.16.camel@perseus.fritz.box> <1392898704.2508.26.camel@perseus.fritz.box> <530625D0.7020808@molgen.mpg.de> <1392946952.2495.3.camel@perseus.fritz.box> <53076D91.7050703@molgen.mpg.de> <53107D4A.90904@molgen.mpg.de> <20140228132906.GM15017@sh-el6.eng.rdu2.redhat.com> Mime-Version: 1.0 Content-Type: multipart/signed; protocol="application/pkcs7-signature"; micalg=sha1; boundary="------------ms060500050902020704000207" Return-path: In-Reply-To: <20140228132906.GM15017@sh-el6.eng.rdu2.redhat.com> Sender: autofs-owner@vger.kernel.org List-ID: To: Alexander Viro Cc: Ian Kent , autofs This is a cryptographically signed message in MIME format. --------------ms060500050902020704000207 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: quoted-printable Am 28.02.2014 14:29, schrieb Alexander Viro: > On Fri, Feb 28, 2014 at 01:12:58PM +0100, Donald Buczek wrote: > >> Obviously, "cleared mounted on dentry" is missing. >> >> It looks like we enter put_mountpoint() but don't get to >> dentry->d_flags &=3D ~DCACHE_MOUNTED; >> >> mp->m_count is not zero probably. >> >> What does it mean? The mount is still locked but not in the mount hash= ? > No, it means that something else is mounted on the same dentry (in anot= her > part of mount tree, obviously). > > If you mount the same fs on two different mountpoints, e.g. > mount /dev/sda1 /mnt > mount /dev/sda1 /tmp/foo > you will have the same dentries seen in two places. Now, > mount /dev/sdb11 /mnt/a > mount /dev/sdc5 /tmp/foo/a > > and you've got two different filesystems mounted on two different place= s > (/mnt/a and /tmp/foo/a). These two places have different vfsmounts, > but the same dentry. struct mountpoint is associated with dentry, so > it's also the same for both. And it serves as a mountpoint for two > vfsmounts - one for fs from sdb11, another for fs from sdc5. > > Now umount /mnt/a; one of those two vfsmounts is gone now. struct moun= tpoint > survives, of course, and dentry is *still* a mountpoint. sdc5 is still= > mounted on /tmp/foo/a, after all... Thanks. So I guess, the idea of "struct mountpoint" is to make the=20 dentries smaller by not having the mount count embedded in each one,=20 99.9% not needing it? OMG, I've just found this in the log: > 91286 2014-02-26T14:09:56.830515+01:00 kasslerbraten kernel:=20 > [195977.007799] pid 8644: d_set_mounted: dentry=3Dffff88004690c710 root= > 91287 2014-02-26T14:09:56.830527+01:00 kasslerbraten kernel:=20 > [195977.007802] pid 8644: d_set_mounted: set mounted on=20 > dentry=3Dffff88004690c710 root > 91288 2014-02-26T14:09:56.830529+01:00 kasslerbraten kernel:=20 > [195977.007873] pid 8644: put_mountpoint: mp=3Dffff8800b8aa1a38 > 91289 2014-02-26T14:09:56.830530+01:00 kasslerbraten kernel:=20 > [195977.007877] pid 8644: d_set_mounted: dentry=3Dffff8800ca45e810 tmp > 91290 2014-02-26T14:09:56.830535+01:00 kasslerbraten kernel:=20 > [195977.007878] pid 8644: d_set_mounted: set mounted on=20 > dentry=3Dffff8800ca45e810 tmp > 91291 2014-02-26T14:09:56.830536+01:00 kasslerbraten kernel:=20 > [195977.007881] pid 8644: put_mountpoint: mp=3Dffff8800b8aa1a38 > 91292 2014-02-26T14:09:56.830537+01:00 kasslerbraten kernel:=20 > [195977.007900] pid 8644: d_set_mounted: dentry=3Dffff880046960450=20 > old-root-mjn70Q > 91293 2014-02-26T14:09:56.830538+01:00 kasslerbraten kernel:=20 > [195977.007901] pid 8644: d_set_mounted: set mounted on=20 > dentry=3Dffff880046960450 old-root-mjn70Q > 91294 2014-02-26T14:09:56.830539+01:00 kasslerbraten kernel:=20 > [195977.007903] pid 8644: put_mountpoint: mp=3Dffff8800a5f1dbd0 > 91295 2014-02-26T14:09:56.830540+01:00 kasslerbraten kernel:=20 > [195977.007904] pid 8644: put_mountpoint: cleared mounted on=20 > dentry=3Dffff88004690c710 root > 91296 2014-02-26T14:09:56.830541+01:00 kasslerbraten kernel:=20 > [195977.007905] pid 8644: put_mountpoint: mp=3Dffff8800a5f1da90 > 91297 2014-02-26T14:09:56.830541+01:00 kasslerbraten kernel:=20 > [195977.007954] pid 8644: put_mountpoint: mp=3D0000014f00490049 > 91298 2014-02-26T14:09:56.830542+01:00 kasslerbraten kernel:=20 > [195977.007955] pid 8644: put_mountpoint: mp=3D0000000000000006 > 91299 2014-02-26T14:09:56.830543+01:00 kasslerbraten kernel:=20 > [195977.007961] pid 8644: put_mountpoint: mp=3Dffff8800a5f1dbd0 > 91300 2014-02-26T14:09:56.830544+01:00 kasslerbraten kernel:=20 > [195977.007963] pid 8644: put_mountpoint: mp=3Dffff8800a6023d10 > 91301 2014-02-26T14:09:56.830544+01:00 kasslerbraten kernel:=20 > [195977.007963] pid 8644: put_mountpoint: mp=3Dffff8800a6023d10 > 91302 2014-02-26T14:09:56.830545+01:00 kasslerbraten kernel:=20 > [195977.007964] pid 8644: put_mountpoint: mp=3Dffff8800a5f1dbd0 What is this? Where does "root" and "old-root-" come from? Why does 8644 = survive dereferencing mp=3D0000000000000006 from the kernel? Is this stil= l=20 related to autofs? D. --=20 Donald Buczek buczek@molgen.mpg.de Tel: +49 30 8413 1433 --------------ms060500050902020704000207 Content-Type: application/pkcs7-signature; name="smime.p7s" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="smime.p7s" Content-Description: S/MIME Cryptographic Signature MIAGCSqGSIb3DQEHAqCAMIACAQExCzAJBgUrDgMCGgUAMIAGCSqGSIb3DQEHAQAAoIIOKjCC BCEwggMJoAMCAQICAgDHMA0GCSqGSIb3DQEBBQUAMHExCzAJBgNVBAYTAkRFMRwwGgYDVQQK ExNEZXV0c2NoZSBUZWxla29tIEFHMR8wHQYDVQQLExZULVRlbGVTZWMgVHJ1c3QgQ2VudGVy MSMwIQYDVQQDExpEZXV0c2NoZSBUZWxla29tIFJvb3QgQ0EgMjAeFw0wNjEyMTkxMDI5MDBa Fw0xOTA2MzAyMzU5MDBaMFoxCzAJBgNVBAYTAkRFMRMwEQYDVQQKEwpERk4tVmVyZWluMRAw DgYDVQQLEwdERk4tUEtJMSQwIgYDVQQDExtERk4tVmVyZWluIFBDQSBHbG9iYWwgLSBHMDEw ggEiMA0GCSqGSIb3DQEBAQUAA4IBDwAwggEKAoIBAQDpm8NnhfkNrvWNVMOWUDU9YuluTO2U 1wBblSJ01CDrNI/W7MAxBAuZgeKmFNJSoCgjhIt0iQReW+DieMF4yxbLKDU5ey2QRdDtoAB6 fL9KDhsAw4bpXCsxEXsM84IkQ4wcOItqaACa7txPeKvSxhObdq3u3ibo7wGvdA/BCaL2a869 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