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authorDan Williams <dan.j.williams@intel.com>2019-06-13 15:56:33 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2019-06-13 17:34:56 -1000
commit50f44ee7248ad2f7984ef081974a6ecd09724b3e (patch)
treeab753d9044434c94c8e6d70ead68173c2af339f6 /drivers/dax
parent1570175abd164b32ea1cc677f9dfd2dc6bd093f5 (diff)
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@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>
Diffstat (limited to 'drivers/dax')
-rw-r--r--drivers/dax/device.c13
1 files changed, 3 insertions, 10 deletions
diff --git a/drivers/dax/device.c b/drivers/dax/device.c
index 996d68ff992a..8465d12fecba 100644
--- a/drivers/dax/device.c
+++ b/drivers/dax/device.c
@@ -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;