mm, dev_pagemap: Do not clear ->mapping on final put

MEMORY_DEVICE_FS_DAX relies on typical page semantics whereby ->mapping
is only ever cleared by truncation, not final put.

Without this fix dax pages may forget their mapping association at the
end of every page pin event.

Move this atypical behavior that HMM wants into the HMM ->page_free()
callback.

Cc: <stable@vger.kernel.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Fixes: d2c997c0f145 ("fs, dax: use page->mapping...")
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Acked-by: Jérôme Glisse <jglisse@redhat.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>

diff --git a/kernel/memremap.c b/kernel/memremap.c
index 5857267..6260363 100644 (file)
--- a/kernel/memremap.c
+++ b/kernel/memremap.c
@@ -339,7 +339,6 @@ void __put_devmap_managed_page(struct page *page)
                __ClearPageActive(page);
                __ClearPageWaiters(page);
 
-               page->mapping = NULL;
                mem_cgroup_uncharge(page);
 
                page->pgmap->page_free(page, page->pgmap->data);

diff --git a/mm/hmm.c b/mm/hmm.c
index de7b6bf..f9d1d89 100644 (file)
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -963,6 +963,8 @@ static void hmm_devmem_free(struct page *page, void *data)
 {
        struct hmm_devmem *devmem = data;
 
+       page->mapping = NULL;
+
        devmem->ops->free(devmem, page);
 }