Commit 063a7d1d authored by Dan Williams's avatar Dan Williams Committed by Linus Torvalds
Browse files

mm/hmm: fix memremap.h, move dev_page_fault_t callback to hmm 

The kbuild robot reported the following on a development branch that used
memremap.h in a new path:

   In file included from arch/m68k/include/asm/pgtable_mm.h:148:0,
                     from arch/m68k/include/asm/pgtable.h:5,
                     from include/linux/memremap.h:7,
                     from drivers//dax/bus.c:3:
    arch/m68k/include/asm/motorola_pgtable.h: In function 'pgd_offset':
 >> arch/m68k/include/asm/motorola_pgtable.h:199:11: error: dereferencing pointer to incomplete type 'const struct mm_struct'
      return mm->pgd + pgd_index(address);
               ^~

The ->page_fault() callback is specific to HMM.  Move it to 'struct
hmm_devmem' where the unusual asm/pgtable.h dependency can be contained in
include/linux/hmm.h.  Longer term refactoring this dependency out of HMM
is recommended, but in the meantime memremap.h remains generic.

Link: http://lkml.kernel.org/r/154534090899.3120190.6652620807617715272.stgit@dwillia2-desk3.amr.corp.intel.com


Fixes: 5042db43 ("mm/ZONE_DEVICE: new type of ZONE_DEVICE memory...")
Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
Reviewed-by: default avatar"Jérôme Glisse" <jglisse@redhat.com>
Cc: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent c86aa7bb

include/linux/hmm.h

+24 −0
Original line number Diff line number Diff line
@@ -69,6 +69,7 @@ 
#define LINUX_HMM_H



#include <linux/kconfig.h>

#include <asm/pgtable.h>



#if IS_ENABLED(CONFIG_HMM)
@@ -486,6 +487,7 @@ struct hmm_devmem_ops { 
 * @device: device to bind resource to

 * @ops: memory operations callback

 * @ref: per CPU refcount

 * @page_fault: callback when CPU fault on an unaddressable device page

 *

 * This an helper structure for device drivers that do not wish to implement

 * the gory details related to hotplugging new memoy and allocating struct
@@ -493,7 +495,28 @@ struct hmm_devmem_ops { 
 *

 * Device drivers can directly use ZONE_DEVICE memory on their own if they

 * wish to do so.

 *

 * The page_fault() callback must migrate page back, from device memory to

 * system memory, so that the CPU can access it. This might fail for various

 * reasons (device issues,  device have been unplugged, ...). When such error

 * conditions happen, the page_fault() callback must return VM_FAULT_SIGBUS and

 * set the CPU page table entry to "poisoned".

 *

 * Note that because memory cgroup charges are transferred to the device memory,

 * this should never fail due to memory restrictions. However, allocation

 * of a regular system page might still fail because we are out of memory. If

 * that happens, the page_fault() callback must return VM_FAULT_OOM.

 *

 * The page_fault() callback can also try to migrate back multiple pages in one

 * chunk, as an optimization. It must, however, prioritize the faulting address

 * over all the others.

 */

typedef int (*dev_page_fault_t)(struct vm_area_struct *vma,

				unsigned long addr,

				const struct page *page,

				unsigned int flags,

				pmd_t *pmdp);



struct hmm_devmem {

	struct completion		completion;

	unsigned long			pfn_first;
@@ -503,6 +526,7 @@ struct hmm_devmem { 
	struct dev_pagemap		pagemap;

	const struct hmm_devmem_ops	*ops;

	struct percpu_ref		ref;

	dev_page_fault_t		page_fault;

};



/*

include/linux/memremap.h

+0 −32
Original line number Diff line number Diff line
@@ -4,8 +4,6 @@ 
#include <linux/ioport.h>

#include <linux/percpu-refcount.h>



#include <asm/pgtable.h>



struct resource;

struct device;
@@ -66,47 +64,18 @@ enum memory_type { 
};



/*

 * For MEMORY_DEVICE_PRIVATE we use ZONE_DEVICE and extend it with two

 * callbacks:

 *   page_fault()

 *   page_free()

 *

 * Additional notes about MEMORY_DEVICE_PRIVATE may be found in

 * include/linux/hmm.h and Documentation/vm/hmm.rst. There is also a brief

 * explanation in include/linux/memory_hotplug.h.

 *

 * The page_fault() callback must migrate page back, from device memory to

 * system memory, so that the CPU can access it. This might fail for various

 * reasons (device issues,  device have been unplugged, ...). When such error

 * conditions happen, the page_fault() callback must return VM_FAULT_SIGBUS and

 * set the CPU page table entry to "poisoned".

 *

 * Note that because memory cgroup charges are transferred to the device memory,

 * this should never fail due to memory restrictions. However, allocation

 * of a regular system page might still fail because we are out of memory. If

 * that happens, the page_fault() callback must return VM_FAULT_OOM.

 *

 * The page_fault() callback can also try to migrate back multiple pages in one

 * chunk, as an optimization. It must, however, prioritize the faulting address

 * over all the others.

 *

 *

 * The page_free() callback is called once the page refcount reaches 1

 * (ZONE_DEVICE pages never reach 0 refcount unless there is a refcount bug.

 * This allows the device driver to implement its own memory management.)

 *

 * For MEMORY_DEVICE_PUBLIC only the page_free() callback matter.

 */

typedef int (*dev_page_fault_t)(struct vm_area_struct *vma,

				unsigned long addr,

				const struct page *page,

				unsigned int flags,

				pmd_t *pmdp);

typedef void (*dev_page_free_t)(struct page *page, void *data);



/**

 * struct dev_pagemap - metadata for ZONE_DEVICE mappings

 * @page_fault: callback when CPU fault on an unaddressable device page

 * @page_free: free page callback when page refcount reaches 1

 * @altmap: pre-allocated/reserved memory for vmemmap allocations

 * @res: physical address range covered by @ref
@@ -117,7 +86,6 @@ typedef void (*dev_page_free_t)(struct page *page, void *data); 
 * @type: memory type: see MEMORY_* in memory_hotplug.h

 */

struct dev_pagemap {

	dev_page_fault_t page_fault;

	dev_page_free_t page_free;

	struct vmem_altmap altmap;

	bool altmap_valid;

kernel/memremap.c

+5 −1
Original line number Diff line number Diff line
@@ -11,6 +11,7 @@ 
#include <linux/types.h>

#include <linux/wait_bit.h>

#include <linux/xarray.h>

#include <linux/hmm.h>



static DEFINE_XARRAY(pgmap_array);

#define SECTION_MASK ~((1UL << PA_SECTION_SHIFT) - 1)
@@ -24,6 +25,9 @@ vm_fault_t device_private_entry_fault(struct vm_area_struct *vma, 
		       pmd_t *pmdp)

{

	struct page *page = device_private_entry_to_page(entry);

	struct hmm_devmem *devmem;



	devmem = container_of(page->pgmap, typeof(*devmem), pagemap);



	/*

	 * The page_fault() callback must migrate page back to system memory
@@ -39,7 +43,7 @@ vm_fault_t device_private_entry_fault(struct vm_area_struct *vma, 
	 * There is a more in-depth description of what that callback can and

	 * cannot do, in include/linux/memremap.h

	 */

	return page->pgmap->page_fault(vma, addr, page, flags, pmdp);

	return devmem->page_fault(vma, addr, page, flags, pmdp);

}

EXPORT_SYMBOL(device_private_entry_fault);

#endif /* CONFIG_DEVICE_PRIVATE */

mm/hmm.c

+2 −2
Original line number Diff line number Diff line
@@ -1087,10 +1087,10 @@ struct hmm_devmem *hmm_devmem_add(const struct hmm_devmem_ops *ops, 
	devmem->pfn_first = devmem->resource->start >> PAGE_SHIFT;

	devmem->pfn_last = devmem->pfn_first +

			   (resource_size(devmem->resource) >> PAGE_SHIFT);

	devmem->page_fault = hmm_devmem_fault;



	devmem->pagemap.type = MEMORY_DEVICE_PRIVATE;

	devmem->pagemap.res = *devmem->resource;

	devmem->pagemap.page_fault = hmm_devmem_fault;

	devmem->pagemap.page_free = hmm_devmem_free;

	devmem->pagemap.altmap_valid = false;

	devmem->pagemap.ref = &devmem->ref;
@@ -1141,10 +1141,10 @@ struct hmm_devmem *hmm_devmem_add_resource(const struct hmm_devmem_ops *ops, 
	devmem->pfn_first = devmem->resource->start >> PAGE_SHIFT;

	devmem->pfn_last = devmem->pfn_first +

			   (resource_size(devmem->resource) >> PAGE_SHIFT);

	devmem->page_fault = hmm_devmem_fault;



	devmem->pagemap.type = MEMORY_DEVICE_PUBLIC;

	devmem->pagemap.res = *devmem->resource;

	devmem->pagemap.page_fault = hmm_devmem_fault;

	devmem->pagemap.page_free = hmm_devmem_free;

	devmem->pagemap.altmap_valid = false;

	devmem->pagemap.ref = &devmem->ref;

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