mm/devm_memremap_pages: fix final page put race
Logan noticed that devm_memremap_pages_release() kills the percpu_ref
drops all the page references that were acquired at init and then
immediately proceeds to unplug, arch_remove_memory(), the backing pages
for the pagemap. If for some reason device shutdown actually collides
with a busy / elevated-ref-count page then arch_remove_memory() should
be deferred until after that reference is dropped.
As it stands the "wait for last page ref drop" happens *after*
devm_memremap_pages_release() returns, which is obviously too late and
can lead to crashes.
Fix this situation by assigning the responsibility to wait for the
percpu_ref to go idle to devm_memremap_pages() with a new ->cleanup()
callback. Implement the new cleanup callback for all
devm_memremap_pages() users: pmem, devdax, hmm, and p2pdma.
Link: http://lkml.kernel.org/r/155727339156.292046.5432007428235387859.stgit@dwillia2-desk3.amr.corp.intel.com
Fixes: 41e94a851304 ("add devm_memremap_pages")
Signed-off-by: Dan Williams <dan.j.williams at intel.com>
Reported-by: Logan Gunthorpe <logang at deltatee.com>
Reviewed-by: Ira Weiny <ira.weiny at intel.com>
Reviewed-by: Logan Gunthorpe <logang at deltatee.com>
Cc: Bjorn Helgaas <bhelgaas at google.com>
Cc: "Jérôme Glisse" <jglisse at redhat.com>
Cc: Christoph Hellwig <hch at lst.de>
Cc: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
Cc: "Rafael J. Wysocki" <rafael at kernel.org>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
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