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mm/devm_memremap_pages: fix final page put race

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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: 41e94a8513 ("add devm_memremap_pages")
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Reported-by: Logan Gunthorpe <logang@deltatee.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: "Jérôme Glisse" <jglisse@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Dan Williams
2019-06-13 15:56:33 -07:00
committed by Linus Torvalds
parent 1570175abd
commit 50f44ee724
7 changed files with 38 additions and 44 deletions
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2
include/linux/memremap.h
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@@ -81,6 +81,7 @@ typedef void (*dev_page_free_t)(struct page *page, void *data);
* @res: physical address range covered by @ref
* @ref: reference count that pins the devm_memremap_pages() mapping
* @kill: callback to transition @ref to the dead state
* @cleanup: callback to wait for @ref to be idle and reap it
* @dev: host device of the mapping for debug
* @data: private data pointer for page_free()
* @type: memory type: see MEMORY_* in memory_hotplug.h
@@ -92,6 +93,7 @@ struct dev_pagemap {
struct resource res;
struct percpu_ref *ref;
void (*kill)(struct percpu_ref *ref);
void (*cleanup)(struct percpu_ref *ref);
struct device *dev;
void *data;
enum memory_type type;