On 22/05/18 10:56 AM, Dan Williams wrote: > On Tue, May 22, 2018 at 9:42 AM, Logan Gunthorpe <logang@xxxxxxxxxxxx> wrote: >> Hey Dan, >> >> On 21/05/18 06:07 PM, Dan Williams wrote: >>> Without this change we could fail to register the teardown of >>> devm_memremap_pages(). The likelihood of hitting this failure is tiny >>> as small memory allocations almost always succeed. However, the impact >>> of the failure is large given any future reconfiguration, or >>> disable/enable, of an nvdimm namespace will fail forever as subsequent >>> calls to devm_memremap_pages() will fail to setup the pgmap_radix >>> since there will be stale entries for the physical address range. >> >> Sorry, I don't follow this. The change only seems to prevent a warning >> from occurring in this situation. Won't pgmap_radix_release() still be >> called regardless of whether this patch is applied? > > devm_add_action() does not call the release function, > devm_add_action_or_reset() does. Oh, yes. Thanks I see that now. > Ah, true, good catch! > > We should manually kill in the !registered case. I think this means we > need to pass in the custom kill routine, because for the pmem driver > it's blk_freeze_queue_start(). It may be cleaner to just have the caller call the specific kill function if devm_memremap_pages fails... Though, I don't fully understand how the nvdimm pmem driver cleans up the percpu counter. Logan
