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

BugLink: https://bugs.launchpad.net/bugs/1835972
commit 2fa147bdbf672c53386a8f5f2c7fe358004c3ef8 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

diff --git a/kernel/memremap.c b/kernel/memremap.c
index 8edd223eb81c3426a032fbe64d22d8091cfb79bd..9f775c378b9fbb10443fa3c45b5e76727e1ae1e7 100644 (file)
--- a/kernel/memremap.c
+++ b/kernel/memremap.c
@@ -534,7 +534,6 @@ void put_zone_device_private_or_public_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 15ffae83499def6643c6a39726c8b13ab1922817..333141b24713a6f7d94e9f0de0a15c63e56de5c0 100644 (file)
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -796,6 +796,8 @@ static void hmm_devmem_free(struct page *page, void *data)
 {
        struct hmm_devmem *devmem = data;
 
+       page->mapping = NULL;
+
        devmem->ops->free(devmem, page);
 }