[PATCH] mm: Cleanup __put_devmap_managed_page() vs ->page_free()

Dan Williams
2019-11-14T00:21:46Z

After the removal of the device-public infrastructure there are only 2
->page_free() call backs in the kernel. One of those is a device-private
callback in the nouveau driver, the other is a generic wakeup needed in
the DAX case. In the hopes that all ->page_free() callbacks can be
migrated to common core kernel functionality, move the device-private
specific actions in __put_devmap_managed_page() under the
is_device_private_page() conditional, including the ->page_free()
callback. For the other page types just open-code the generic wakeup.

Yes, the wakeup is only needed in the MEMORY_DEVICE_FSDAX case, but it
does no harm in the MEMORY_DEVICE_DEVDAX and MEMORY_DEVICE_PCI_P2PDMA
case.

Cc: Jan Kara <jack@suse.cz>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
Hi John,

This applies on top of today's linux-next and passes my nvdimm unit
tests. That testing noticed that devmap_managed_enable_get() needed a
small fixup as well.

drivers/nvdimm/pmem.c | 6 ------
mm/memremap.c | 22 ++++++++++++----------
2 files changed, 12 insertions(+), 16 deletions(-)

diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index f9f76f6ba07b..21db1ce8c0ae 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -338,13 +338,7 @@ static void pmem_release_disk(void *__pmem)
put_disk(pmem->disk);
}

-static void pmem_pagemap_page_free(struct page *page)
-{
- wake_up_var(&page->_refcount);
-}
-
static const struct dev_pagemap_ops fsdax_pagemap_ops = {
- .page_free = pmem_pagemap_page_free,
.kill = pmem_pagemap_kill,
.cleanup = pmem_pagemap_cleanup,
};
diff --git a/mm/memremap.c b/mm/memremap.c
index 022e78e68ea0..6e6f3d6fdb73 100644
--- a/mm/memremap.c
+++ b/mm/memremap.c
@@ -27,7 +27,8 @@ static void devmap_managed_enable_put(void)

static int devmap_managed_enable_get(struct dev_pagemap *pgmap)
{
- if (!pgmap->ops || !pgmap->ops->page_free) {
+ if (!pgmap->ops || (pgmap->type == MEMORY_DEVICE_PRIVATE
+ && !pgmap->ops->page_free)) {
WARN(1, "Missing page_free method\n");
return -EINVAL;
}
@@ -449,12 +450,6 @@ void __put_devmap_managed_page(struct page *page)
* holds a reference on the page.
*/
if (count == 1) {
- /* Clear Active bit in case of parallel mark_page_accessed */
- __ClearPageActive(page);
- __ClearPageWaiters(page);
-
- mem_cgroup_uncharge(page);
-
/*
* When a device_private page is freed, the page->mapping field
* may still contain a (stale) mapping value. For example, the
@@ -476,10 +471,17 @@ void __put_devmap_managed_page(struct page *page)
* handled differently or not done at all, so there is no need
* to clear page->mapping.
*/
- if (is_device_private_page(page))
- page->mapping = NULL;
+ if (is_device_private_page(page)) {
+ /* Clear Active bit in case of parallel mark_page_accessed */
+ __ClearPageActive(page);
+ __ClearPageWaiters(page);

- page->pgmap->ops->page_free(page);
+ mem_cgroup_uncharge(page);
+
+ page->mapping = NULL;
+ page->pgmap->ops->page_free(page);
+ } else
+ wake_up_var(&page->_refcount);
} else if (!count)
__put_page(page);
}