Hi mm folks,
I'm looking at ZONE_DEVICE support for arm64, and trying to make sense
of a build failure has led me down the rabbit hole of pfn_t.h, and
specifically __HAVE_ARCH_PTE_DEVMAP in this first instance.
The failure itself is a link error in remove_migration_pte() due to a
missing definition of pte_mkdevmap(), but I'm a little confused at the
fact that it's explicitly declared without a definition, as if that
breakage is deliberate.
So, is the !__HAVE_ARCH_PTE_DEVMAP case actually expected to work? If
not, then it seems to me that the relevant code could just be gated by
CONFIG_ZONE_DEVICE directly to remove the confusion. If it is, though,
then what should the generic definitions of p??_mkdevmap() be? I guess
either way I still need to figure out the implications of _PAGE_DEVMAP
at the arch end and whether/how arm64 should implement it, but given
this initial hurdle it's not clear exactly where to go next.
Tangentially, is it also right that is_device_{public,private}_page()
can still get non-stub definitions even with
CONFIG_DEVICE_{PUBLIC,PRIVATE} disabled? As it happens, the patch below
is enough to dodge the build failure for my configuration (i.e.
CONFIG_FS_DAX && !CONFIG_HMM) by optimising the offending call away,
however I'm not sure I'd want to rely on that; conceptually, though, it
does still seem like it might be appropriate.
Thanks,
Robin.
----->8-----
From: Robin Murphy <robin.murphy@xxxxxxx>
Date: Wed, 31 Oct 2018 15:57:17 +0000
Subject: [PATCH] mm: Clean up is_device_*_page() definitions
Refactor is_device_{public,private}_page() with is_pci_p2pdma_page()
to make them all consistent in depending on their respective config
options even when CONFIG_DEV_PAGEMAP_OPS is enabled for other reasons.
This allows a little more compile-time optimisation as well as the
conceptual and cosmetic cleanup.
Signed-off-by: Robin Murphy <robin.murphy@xxxxxxx>
---
include/linux/mm.h | 52 ++++++++++++++++++++++------------------------
1 file changed, 25 insertions(+), 27 deletions(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 1e52b8fd1685..15a49ed5436c 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -879,32 +879,6 @@ static inline bool put_devmap_managed_page(struct
page *page)
}
return false;
}
-
-static inline bool is_device_private_page(const struct page *page)
-{
- return is_zone_device_page(page) &&
- page->pgmap->type == MEMORY_DEVICE_PRIVATE;
-}
-
-static inline bool is_device_public_page(const struct page *page)
-{
- return is_zone_device_page(page) &&
- page->pgmap->type == MEMORY_DEVICE_PUBLIC;
-}
-
-#ifdef CONFIG_PCI_P2PDMA
-static inline bool is_pci_p2pdma_page(const struct page *page)
-{
- return is_zone_device_page(page) &&
- page->pgmap->type == MEMORY_DEVICE_PCI_P2PDMA;
-}
-#else /* CONFIG_PCI_P2PDMA */
-static inline bool is_pci_p2pdma_page(const struct page *page)
-{
- return false;
-}
-#endif /* CONFIG_PCI_P2PDMA */
-
#else /* CONFIG_DEV_PAGEMAP_OPS */
static inline void dev_pagemap_get_ops(void)
{
@@ -918,22 +892,46 @@ static inline bool put_devmap_managed_page(struct
page *page)
{
return false;
}
+#endif /* CONFIG_DEV_PAGEMAP_OPS */
+#if defined(CONFIG_DEV_PAGEMAP_OPS) && defined(CONFIG_DEVICE_PRIVATE)
+static inline bool is_device_private_page(const struct page *page)
+{
+ return is_zone_device_page(page) &&
+ page->pgmap->type == MEMORY_DEVICE_PRIVATE;
+}
+#else
static inline bool is_device_private_page(const struct page *page)
{
return false;
}
+#endif
+#if defined(CONFIG_DEV_PAGEMAP_OPS) && defined(CONFIG_DEVICE_PUBLIC)
+static inline bool is_device_public_page(const struct page *page)
+{
+ return is_zone_device_page(page) &&
+ page->pgmap->type == MEMORY_DEVICE_PUBLIC;
+}
+#else
static inline bool is_device_public_page(const struct page *page)
{
return false;
}
+#endif
+#if defined(CONFIG_DEV_PAGEMAP_OPS) && defined(CONFIG_PCI_P2PDMA)
+static inline bool is_pci_p2pdma_page(const struct page *page)
+{
+ return is_zone_device_page(page) &&
+ page->pgmap->type == MEMORY_DEVICE_PCI_P2PDMA;
+}
+#else
static inline bool is_pci_p2pdma_page(const struct page *page)
{
return false;
}
-#endif /* CONFIG_DEV_PAGEMAP_OPS */
+#endif
static inline void get_page(struct page *page)
{
--
2.19.1.dirty
