On Fri, 29 Jul 2005 15:35:25 +0200 christophe varoqui <christophe.varoqui@xxxxxxx> wrote > Subject: [dm-devel] [Bug 164617] extracting tar image causes paths > state change to [ready][failed] > To: narasimha.murthy@xxxxxx > Cc: device-mapper development <dm-devel@xxxxxxxxxx> > Message-ID: <1122644125.3569.37.camel@zezette> > Content-Type: text/plain > > Will provide the following additional info : > > Was the daemon runing ? > If so paste a verbose daemon log. > Paste a dmesg too. Talking with Narasimha on the weekly multipathing conference call, it seems this problem only occurs when a second multipath mapped device is manually created via dmsetup to utilize the SAME paths as a multipath mapped device already configured by multipath(8). Seems to me that neither multipath nor multipathd will react well to this configuration since there is but a single path data structure for each physical path and each path structure has but a single link to its multipath data structure. It also seems that the kernel dm code should not be allowing this to happen, that is, a target device should not be used as a target of more than a single device-mapper mapped device. Target devices are claimed for use by but a single exclusive open via a call to bd_claim in open_dev, but the device-mapper uses the same claim holder value for all target devices -- thereby allowing the same device to be a target device of multiple mapped devices. A possible fix here is to use a claim holder value (ptr to mapped device possibly) which is unique for each mapped device -- thereby causing an attempt to create a mapped device using a target device of an already existing mapped device to fail. I can experiment with this and get a patch as soon as I have a host to use.
