diff mbox series

[12/25] memremap: add a migrate_to_ram method to struct dev_pagemap_ops

Message ID 20190626122724.13313-13-hch@lst.de (mailing list archive)
State New, archived
Delegated to: Bjorn Helgaas
Headers show
Series [01/25] mm: remove the unused ARCH_HAS_HMM_DEVICE Kconfig option | expand

Commit Message

Christoph Hellwig June 26, 2019, 12:27 p.m. UTC 
This replaces the hacky ->fault callback, which is currently directly
called from common code through a hmm specific data structure as an
exercise in layering violations.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ralph Campbell <rcampbell@nvidia.com>
---
 include/linux/hmm.h      |  6 ------
 include/linux/memremap.h |  6 ++++++
 include/linux/swapops.h  | 15 ---------------
 kernel/memremap.c        | 35 ++++-------------------------------
 mm/hmm.c                 | 13 +++++--------
 mm/memory.c              |  9 ++-------
 6 files changed, 17 insertions(+), 67 deletions(-)

Comments

Jason Gunthorpe June 27, 2019, 4:29 p.m. UTC | #1 
On Wed, Jun 26, 2019 at 02:27:11PM +0200, Christoph Hellwig wrote:
> This replaces the hacky ->fault callback, which is currently directly
> called from common code through a hmm specific data structure as an
> exercise in layering violations.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> Reviewed-by: Ralph Campbell <rcampbell@nvidia.com>
> ---
>  include/linux/hmm.h      |  6 ------
>  include/linux/memremap.h |  6 ++++++
>  include/linux/swapops.h  | 15 ---------------
>  kernel/memremap.c        | 35 ++++-------------------------------
>  mm/hmm.c                 | 13 +++++--------
>  mm/memory.c              |  9 ++-------
>  6 files changed, 17 insertions(+), 67 deletions(-)

Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>
 
I'ver heard there are some other use models for fault() here beyond
migrate to ram, but we can rename it if we ever see them.

> +static vm_fault_t hmm_devmem_migrate_to_ram(struct vm_fault *vmf)
>  {
> -	struct hmm_devmem *devmem = page->pgmap->data;
> +	struct hmm_devmem *devmem = vmf->page->pgmap->data;
>  
> -	return devmem->ops->fault(devmem, vma, addr, page, flags, pmdp);
> +	return devmem->ops->fault(devmem, vmf->vma, vmf->address, vmf->page,
> +			vmf->flags, vmf->pmd);
>  }

Next cycle we should probably rename this fault to migrate_to_ram as
well and pass in the vmf..

Jason
Christoph Hellwig June 27, 2019, 4:53 p.m. UTC | #2 
On Thu, Jun 27, 2019 at 04:29:45PM +0000, Jason Gunthorpe wrote:
> I'ver heard there are some other use models for fault() here beyond
> migrate to ram, but we can rename it if we ever see them.

Well, it absolutely needs to migrate to some piece of addressable
and coherent memory, so ram might be a nice shortcut for that.

> > +static vm_fault_t hmm_devmem_migrate_to_ram(struct vm_fault *vmf)
> >  {
> > -	struct hmm_devmem *devmem = page->pgmap->data;
> > +	struct hmm_devmem *devmem = vmf->page->pgmap->data;
> >  
> > -	return devmem->ops->fault(devmem, vma, addr, page, flags, pmdp);
> > +	return devmem->ops->fault(devmem, vmf->vma, vmf->address, vmf->page,
> > +			vmf->flags, vmf->pmd);
> >  }
> 
> Next cycle we should probably rename this fault to migrate_to_ram as
> well and pass in the vmf..

That ->fault op goes away entirely in one of the next patches in the
series.
diff mbox series

Patch

diff --git a/include/linux/hmm.h b/include/linux/hmm.h
index 44a5ac738bb5..ba19c19e24ed 100644
--- a/include/linux/hmm.h
+++ b/include/linux/hmm.h
@@ -692,11 +692,6 @@  struct hmm_devmem_ops {
  * chunk, as an optimization. It must, however, prioritize the faulting address
  * over all the others.
  */
-typedef vm_fault_t (*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;
@@ -707,7 +702,6 @@  struct hmm_devmem {
 	struct dev_pagemap		pagemap;
 	const struct hmm_devmem_ops	*ops;
 	struct percpu_ref		ref;
-	dev_page_fault_t		page_fault;
 };
 
 /*
diff --git a/include/linux/memremap.h b/include/linux/memremap.h
index b8666a0d8665..ac985bd03a7f 100644
--- a/include/linux/memremap.h
+++ b/include/linux/memremap.h
@@ -80,6 +80,12 @@  struct dev_pagemap_ops {
 	 * Wait for refcount in struct dev_pagemap to be idle and reap it.
 	 */
 	void (*cleanup)(struct dev_pagemap *pgmap);
+
+	/*
+	 * Used for private (un-addressable) device memory only.  Must migrate
+	 * the page back to a CPU accessible page.
+	 */
+	vm_fault_t (*migrate_to_ram)(struct vm_fault *vmf);
 };
 
 /**
diff --git a/include/linux/swapops.h b/include/linux/swapops.h
index 4d961668e5fc..15bdb6fe71e5 100644
--- a/include/linux/swapops.h
+++ b/include/linux/swapops.h
@@ -129,12 +129,6 @@  static inline struct page *device_private_entry_to_page(swp_entry_t entry)
 {
 	return pfn_to_page(swp_offset(entry));
 }
-
-vm_fault_t device_private_entry_fault(struct vm_area_struct *vma,
-		       unsigned long addr,
-		       swp_entry_t entry,
-		       unsigned int flags,
-		       pmd_t *pmdp);
 #else /* CONFIG_DEVICE_PRIVATE */
 static inline swp_entry_t make_device_private_entry(struct page *page, bool write)
 {
@@ -164,15 +158,6 @@  static inline struct page *device_private_entry_to_page(swp_entry_t entry)
 {
 	return NULL;
 }
-
-static inline vm_fault_t device_private_entry_fault(struct vm_area_struct *vma,
-				     unsigned long addr,
-				     swp_entry_t entry,
-				     unsigned int flags,
-				     pmd_t *pmdp)
-{
-	return VM_FAULT_SIGBUS;
-}
 #endif /* CONFIG_DEVICE_PRIVATE */
 
 #ifdef CONFIG_MIGRATION
diff --git a/kernel/memremap.c b/kernel/memremap.c
index 3219a4c91d07..c06a5487dda7 100644
--- a/kernel/memremap.c
+++ b/kernel/memremap.c
@@ -11,7 +11,6 @@ 
 #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)
@@ -46,36 +45,6 @@  static int devmap_managed_enable_get(struct device *dev, struct dev_pagemap *pgm
 }
 #endif /* CONFIG_DEV_PAGEMAP_OPS */
 
-#if IS_ENABLED(CONFIG_DEVICE_PRIVATE)
-vm_fault_t device_private_entry_fault(struct vm_area_struct *vma,
-		       unsigned long addr,
-		       swp_entry_t entry,
-		       unsigned int flags,
-		       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
-	 * so that CPU can access it. This might fail for various reasons
-	 * (device issue, device was unsafely unplugged, ...). When such
-	 * error conditions happen, the callback must return VM_FAULT_SIGBUS.
-	 *
-	 * Note that because memory cgroup charges are accounted to the device
-	 * memory, this should never fail because of memory restrictions (but
-	 * allocation of regular system page might still fail because we are
-	 * out of memory).
-	 *
-	 * There is a more in-depth description of what that callback can and
-	 * cannot do, in include/linux/memremap.h
-	 */
-	return devmem->page_fault(vma, addr, page, flags, pmdp);
-}
-#endif /* CONFIG_DEVICE_PRIVATE */
-
 static void pgmap_array_delete(struct resource *res)
 {
 	xa_store_range(&pgmap_array, PHYS_PFN(res->start), PHYS_PFN(res->end),
@@ -193,6 +162,10 @@  void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
 			WARN(1, "Device private memory not supported\n");
 			return ERR_PTR(-EINVAL);
 		}
+		if (!pgmap->ops || !pgmap->ops->migrate_to_ram) {
+			WARN(1, "Missing migrate_to_ram method\n");
+			return ERR_PTR(-EINVAL);
+		}
 		break;
 	case MEMORY_DEVICE_FS_DAX:
 		if (!IS_ENABLED(CONFIG_ZONE_DEVICE) ||
diff --git a/mm/hmm.c b/mm/hmm.c
index 5b0bd5f6a74f..96633ee066d8 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -1366,15 +1366,12 @@  static void hmm_devmem_ref_kill(struct dev_pagemap *pgmap)
 	percpu_ref_kill(pgmap->ref);
 }
 
-static vm_fault_t hmm_devmem_fault(struct vm_area_struct *vma,
-			    unsigned long addr,
-			    const struct page *page,
-			    unsigned int flags,
-			    pmd_t *pmdp)
+static vm_fault_t hmm_devmem_migrate_to_ram(struct vm_fault *vmf)
 {
-	struct hmm_devmem *devmem = page->pgmap->data;
+	struct hmm_devmem *devmem = vmf->page->pgmap->data;
 
-	return devmem->ops->fault(devmem, vma, addr, page, flags, pmdp);
+	return devmem->ops->fault(devmem, vmf->vma, vmf->address, vmf->page,
+			vmf->flags, vmf->pmd);
 }
 
 static void hmm_devmem_free(struct page *page, void *data)
@@ -1388,6 +1385,7 @@  static const struct dev_pagemap_ops hmm_pagemap_ops = {
 	.page_free		= hmm_devmem_free,
 	.kill			= hmm_devmem_ref_kill,
 	.cleanup		= hmm_devmem_ref_exit,
+	.migrate_to_ram		= hmm_devmem_migrate_to_ram,
 };
 
 /*
@@ -1438,7 +1436,6 @@  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;
diff --git a/mm/memory.c b/mm/memory.c
index bd21e7063bf0..293d2936fd6c 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2748,13 +2748,8 @@  vm_fault_t do_swap_page(struct vm_fault *vmf)
 			migration_entry_wait(vma->vm_mm, vmf->pmd,
 					     vmf->address);
 		} else if (is_device_private_entry(entry)) {
-			/*
-			 * For un-addressable device memory we call the pgmap
-			 * fault handler callback. The callback must migrate
-			 * the page back to some CPU accessible page.
-			 */
-			ret = device_private_entry_fault(vma, vmf->address, entry,
-						 vmf->flags, vmf->pmd);
+			vmf->page = device_private_entry_to_page(entry);
+			ret = vmf->page->pgmap->ops->migrate_to_ram(vmf);
 		} else if (is_hwpoison_entry(entry)) {
 			ret = VM_FAULT_HWPOISON;
 		} else {