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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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17
kernel/memremap.c
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@@ -95,6 +95,7 @@ static void devm_memremap_pages_release(void *data)
pgmap->kill(pgmap->ref);
for_each_device_pfn(pfn, pgmap)
put_page(pfn_to_page(pfn));
pgmap->cleanup(pgmap->ref);
/* pages are dead and unused, undo the arch mapping */
align_start = res->start & ~(SECTION_SIZE - 1);
@@ -133,8 +134,8 @@ static void devm_memremap_pages_release(void *data)
* 2/ The altmap field may optionally be initialized, in which case altmap_valid
* must be set to true
*
* 3/ pgmap->ref must be 'live' on entry and will be killed at
* devm_memremap_pages_release() time, or if this routine fails.
* 3/ pgmap->ref must be 'live' on entry and will be killed and reaped
* at devm_memremap_pages_release() time, or if this routine fails.
*
* 4/ res is expected to be a host memory range that could feasibly be
* treated as a "System RAM" range, i.e. not a device mmio range, but
@@ -156,8 +157,10 @@ void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
pgprot_t pgprot = PAGE_KERNEL;
int error, nid, is_ram;
if (!pgmap->ref || !pgmap->kill)
if (!pgmap->ref || !pgmap->kill || !pgmap->cleanup) {
WARN(1, "Missing reference count teardown definition\n");
return ERR_PTR(-EINVAL);
}
align_start = res->start & ~(SECTION_SIZE - 1);
align_size = ALIGN(res->start + resource_size(res), SECTION_SIZE)
@@ -168,14 +171,16 @@ void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
if (conflict_pgmap) {
dev_WARN(dev, "Conflicting mapping in same section\n");
put_dev_pagemap(conflict_pgmap);
return ERR_PTR(-ENOMEM);
error = -ENOMEM;
goto err_array;
}
conflict_pgmap = get_dev_pagemap(PHYS_PFN(align_end), NULL);
if (conflict_pgmap) {
dev_WARN(dev, "Conflicting mapping in same section\n");
put_dev_pagemap(conflict_pgmap);
return ERR_PTR(-ENOMEM);
error = -ENOMEM;
goto err_array;
}
is_ram = region_intersects(align_start, align_size,
@@ -267,6 +272,8 @@ void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
pgmap_array_delete(res);
err_array:
pgmap->kill(pgmap->ref);
pgmap->cleanup(pgmap->ref);
return ERR_PTR(error);
}
EXPORT_SYMBOL_GPL(devm_memremap_pages);