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memremap: add a migrate_to_ram method to struct dev_pagemap_ops

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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>
Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Tested-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
This commit is contained in:
Christoph Hellwig
2019-06-26 14:27:11 +02:00
committed by Jason Gunthorpe
parent f6a55e1a3f
commit 897e6365cd
6 changed files with 17 additions and 67 deletions
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35
kernel/memremap.c
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@@ -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) ||