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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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13
drivers/dax/device.c
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@@ -27,9 +27,8 @@ static void dev_dax_percpu_release(struct percpu_ref *ref)
complete(&dev_dax->cmp);
}
static void dev_dax_percpu_exit(void *data)
static void dev_dax_percpu_exit(struct percpu_ref *ref)
{
struct percpu_ref *ref = data;
struct dev_dax *dev_dax = ref_to_dev_dax(ref);
dev_dbg(&dev_dax->dev, "%s\n", __func__);
@@ -466,18 +465,12 @@ int dev_dax_probe(struct device *dev)
if (rc)
return rc;
rc = devm_add_action_or_reset(dev, dev_dax_percpu_exit, &dev_dax->ref);
if (rc)
return rc;
dev_dax->pgmap.ref = &dev_dax->ref;
dev_dax->pgmap.kill = dev_dax_percpu_kill;
dev_dax->pgmap.cleanup = dev_dax_percpu_exit;
addr = devm_memremap_pages(dev, &dev_dax->pgmap);
if (IS_ERR(addr)) {
devm_remove_action(dev, dev_dax_percpu_exit, &dev_dax->ref);
percpu_ref_exit(&dev_dax->ref);
if (IS_ERR(addr))
return PTR_ERR(addr);
}
inode = dax_inode(dax_dev);
cdev = inode->i_cdev;