Messages in this thread | | | Date | Tue, 22 Jan 2019 08:23:35 +0800 | From | Wei Yang <> | Subject | Re: [PATCH] libnvdimm: Clarify nd_pfn_init() flow |
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On Mon, Jan 21, 2019 at 02:34:06PM -0800, Dan Williams wrote: >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()
Ah, you are right.
-- Wei Yang Help you, Help me
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