There are several scenarios where we need to retrieve and update
metadata associated with a given devm_memremap_pages() mapping, and the
only lookup key available is a pfn in the range:
1/ We want to augment vmemmap_populate() (called via arch_add_memory())
to allocate memmap storage from pre-allocated pages reserved by the
device driver. At vmemmap_alloc_block_buf() time it grabs device pages
rather than page allocator pages. This is in support of
devm_memremap_pages() mappings where the memmap is too large to fit in
main memory (i.e. large persistent memory devices).
2/ Taking a reference against the mapping when inserting device pages
into the address_space radix of a given inode. This facilitates
unmap_mapping_range() and truncate_inode_pages() operations when the
driver is tearing down the mapping.
3/ get_user_pages() operations on ZONE_DEVICE memory require taking a
reference against the mapping so that the driver teardown path can
revoke and drain usage of device pages.
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Dave Chinner <david@xxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
Tested-by: Logan Gunthorpe <logang@xxxxxxxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
---
Changes since v2:
No changes, just a reflow of the patch to fixup the context differences
from: "[-mm PATCH v3 09/25] mm, dax, pmem: introduce pfn_t"
include/linux/io.h | 15 ---------
include/linux/mm.h | 33 ++++++++++++++++++++
kernel/memremap.c | 84 +++++++++++++++++++++++++++++++++++++++++++++++-----
3 files changed, 109 insertions(+), 23 deletions(-)
diff --git a/include/linux/io.h b/include/linux/io.h
index 72c35e0a41d1..32403b5716e5 100644
--- a/include/linux/io.h
+++ b/include/linux/io.h
@@ -90,21 +90,6 @@ void devm_memunmap(struct device *dev, void *addr);
void *__devm_memremap_pages(struct device *dev, struct resource *res);
-#ifdef CONFIG_ZONE_DEVICE
-void *devm_memremap_pages(struct device *dev, struct resource *res);
-#else
-static inline void *devm_memremap_pages(struct device *dev, struct resource *res)
-{
- /*
- * Fail attempts to call devm_memremap_pages() without
- * ZONE_DEVICE support enabled, this requires callers to fall
- * back to plain devm_memremap() based on config
- */
- WARN_ON_ONCE(1);
- return ERR_PTR(-ENXIO);
-}
-#endif
-
/*
* Some systems do not have legacy ISA devices.
* /dev/port is not a valid interface on these systems.
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 1fd3ba9a0924..ddc71b27493d 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -674,6 +674,39 @@ static inline enum zone_type page_zonenum(const struct page *page)
return (page->flags >> ZONES_PGSHIFT) & ZONES_MASK;
}
+struct resource;
+struct device;
+/**
+ * struct dev_pagemap - metadata for ZONE_DEVICE mappings
+ * @dev: host device of the mapping for debug
+ */
+struct dev_pagemap {
+ /* TODO: vmem_altmap and percpu_ref count */
+ struct device *dev;
+};
+
+#ifdef CONFIG_ZONE_DEVICE
+void *devm_memremap_pages(struct device *dev, struct resource *res);
+struct dev_pagemap *find_dev_pagemap(resource_size_t phys);
+#else
+static inline void *devm_memremap_pages(struct device *dev,
+ struct resource *res)
+{
+ /*
+ * Fail attempts to call devm_memremap_pages() without
+ * ZONE_DEVICE support enabled, this requires callers to fall
+ * back to plain devm_memremap() based on config
+ */
+ WARN_ON_ONCE(1);
+ return ERR_PTR(-ENXIO);
+}
+
+static inline struct dev_pagemap *find_dev_pagemap(resource_size_t phys)
+{
+ return NULL;
+}
+#endif
+
#if defined(CONFIG_SPARSEMEM) && !defined(CONFIG_SPARSEMEM_VMEMMAP)
#define SECTION_IN_PAGE_FLAGS
#endif
diff --git a/kernel/memremap.c b/kernel/memremap.c
index 4d3bf3cd09a9..e9be623fda58 100644
--- a/kernel/memremap.c
+++ b/kernel/memremap.c
@@ -10,6 +10,7 @@
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*/
+#include <linux/radix-tree.h>
#include <linux/device.h>
#include <linux/types.h>
#include <linux/io.h>
@@ -154,22 +155,57 @@ pfn_t phys_to_pfn_t(dma_addr_t addr, unsigned long flags)
EXPORT_SYMBOL(phys_to_pfn_t);
#ifdef CONFIG_ZONE_DEVICE
+static DEFINE_MUTEX(pgmap_lock);
+static RADIX_TREE(pgmap_radix, GFP_KERNEL);
+#define SECTION_MASK ~((1UL << PA_SECTION_SHIFT) - 1)
+#define SECTION_SIZE (1UL << PA_SECTION_SHIFT)
+
struct page_map {
struct resource res;
+ struct percpu_ref *ref;
+ struct dev_pagemap pgmap;
};
-static void devm_memremap_pages_release(struct device *dev, void *res)
+static void pgmap_radix_release(struct resource *res)
+{
+ resource_size_t key;
+
+ mutex_lock(&pgmap_lock);
+ for (key = res->start; key <= res->end; key += SECTION_SIZE)
+ radix_tree_delete(&pgmap_radix, key >> PA_SECTION_SHIFT);
+ mutex_unlock(&pgmap_lock);
+}
+
+static void devm_memremap_pages_release(struct device *dev, void *data)
{
- struct page_map *page_map = res;
+ struct page_map *page_map = data;
+ struct resource *res = &page_map->res;
+ resource_size_t align_start, align_size;
+
+ pgmap_radix_release(res);
/* pages are dead and unused, undo the arch mapping */
- arch_remove_memory(page_map->res.start, resource_size(&page_map->res));
+ align_start = res->start & ~(SECTION_SIZE - 1);
+ align_size = ALIGN(resource_size(res), SECTION_SIZE);
+ arch_remove_memory(align_start, align_size);
+}
+
+/* assumes rcu_read_lock() held at entry */
+struct dev_pagemap *find_dev_pagemap(resource_size_t phys)
+{
+ struct page_map *page_map;
+
+ WARN_ON_ONCE(!rcu_read_lock_held());
+
+ page_map = radix_tree_lookup(&pgmap_radix, phys >> PA_SECTION_SHIFT);
+ return page_map ? &page_map->pgmap : NULL;
}
void *devm_memremap_pages(struct device *dev, struct resource *res)
{
int is_ram = region_intersects(res->start, resource_size(res),
"System RAM");
+ resource_size_t key, align_start, align_size;
struct page_map *page_map;
int error, nid;
@@ -189,18 +225,50 @@ void *devm_memremap_pages(struct device *dev, struct resource *res)
memcpy(&page_map->res, res, sizeof(*res));
+ page_map->pgmap.dev = dev;
+ mutex_lock(&pgmap_lock);
+ error = 0;
+ for (key = res->start; key <= res->end; key += SECTION_SIZE) {
+ struct dev_pagemap *dup;
+
+ rcu_read_lock();
+ dup = find_dev_pagemap(key);
+ rcu_read_unlock();
+ if (dup) {
+ dev_err(dev, "%s: %pr collides with mapping for %s\n",
+ __func__, res, dev_name(dup->dev));
+ error = -EBUSY;
+ break;
+ }
+ error = radix_tree_insert(&pgmap_radix, key >> PA_SECTION_SHIFT,
+ page_map);
+ if (error) {
+ dev_err(dev, "%s: failed: %d\n", __func__, error);
+ break;
+ }
+ }
+ mutex_unlock(&pgmap_lock);
+ if (error)
+ goto err_radix;
+
nid = dev_to_node(dev);
if (nid < 0)
nid = numa_mem_id();
- error = arch_add_memory(nid, res->start, resource_size(res), true);
- if (error) {
- devres_free(page_map);
- return ERR_PTR(error);
- }
+ align_start = res->start & ~(SECTION_SIZE - 1);
+ align_size = ALIGN(resource_size(res), SECTION_SIZE);
+ error = arch_add_memory(nid, align_start, align_size, true);
+ if (error)
+ goto err_add_memory;
devres_add(dev, page_map);
return __va(res->start);
+
+ err_add_memory:
+ err_radix:
+ pgmap_radix_release(res);
+ devres_free(page_map);
+ return ERR_PTR(error);
}
EXPORT_SYMBOL(devm_memremap_pages);
#endif /* CONFIG_ZONE_DEVICE */
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>