Messages in this thread | | | From | Dan Williams <> | Date | Mon, 21 Jan 2019 14:34:06 -0800 | Subject | Re: [PATCH] libnvdimm: Clarify nd_pfn_init() flow |
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On Mon, Jan 21, 2019 at 12:57 PM Wei Yang <richard.weiyang@gmail.com> wrote: > > On Mon, Jan 21, 2019 at 10:04:40AM -0800, Dan Williams wrote: > >On Sun, Jan 20, 2019 at 11:51 PM Wei Yang <richardw.yang@linux.intel.com> wrote: > >> On Fri, Jan 18, 2019 at 04:47:23PM -0800, Dan Williams wrote: > >[..] > >> Also, I have one confusion about your saying: two probes. > >> > >> If the two probes are: > >> > >> * for dax%d.%d: 1. nd_dax_probe 2. dax_pmem_probe > >> * for pfn%d.%d: 1. nd_pfn_probe 2. nd_pmem_probe > >> > >> Then, if the first probe fails, the device itself would be destroyed. How the > >> second probe do its job? > >> > >> > rc = nd_pfn_validate(nd_pfn, sig); > >> > if (rc != -ENODEV) > >> > return rc; > > > >Here is an example path for a device-dax instance: > > > > /sys/devices/platform/e820_pmem/ndbus0/region0/dax0.1/dax0.0 > > > >In this case the order of events is: > > > >1/ region0 discovers it contains a pmem namespace and registers namespace0.0 > >2/ The pmem namespace driver calls nd_dax_probe() to check for the > >presence of a device-dax configuration > >3/ If present, nd_pfn_validate() returns 0 and nd_dax_probe() > >registers the dax0.1 device (this is a libnvdimm 'personality device). > >4/ When nd_pmem_probe() sees nd_dax_probe() return 0 it in turn fails > >the probe of namespace0.0 with -ENXIO. All devm allocations during the > >probe of namespace0.0 are released. > > I may have another opinion here. > > The probe return error means the device will not attach to this driver. > But the device itself it not released. > > We allocate devm on one device and those memory will be released when > the device is destroyed. If I am correct. > > This means at this point, pfn_sb's memory still exists in the system. > Even finally we will release it, when namespace0.0 is destroyed.
No, that's not the way devm works. Memory allocated by devm is released at ->probe() failure, or after ->remove()
See the devres_release_all() call in drivers/base/dd.c::really_probe()
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