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-rw-r--r--mm/gup.c50
-rw-r--r--mm/internal.h1
-rw-r--r--mm/migrate_device.c52
3 files changed, 96 insertions, 7 deletions
diff --git a/mm/gup.c b/mm/gup.c
index a9940e3b3181..ecf362688268 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1913,7 +1913,7 @@ static long check_and_migrate_movable_pages(unsigned long nr_pages,
unsigned long isolation_error_count = 0, i;
struct folio *prev_folio = NULL;
LIST_HEAD(movable_page_list);
- bool drain_allow = true;
+ bool drain_allow = true, coherent_pages = false;
int ret = 0;
for (i = 0; i < nr_pages; i++) {
@@ -1923,9 +1923,38 @@ static long check_and_migrate_movable_pages(unsigned long nr_pages,
continue;
prev_folio = folio;
- if (folio_is_longterm_pinnable(folio))
+ /*
+ * Device coherent pages are managed by a driver and should not
+ * be pinned indefinitely as it prevents the driver moving the
+ * page. So when trying to pin with FOLL_LONGTERM instead try
+ * to migrate the page out of device memory.
+ */
+ if (folio_is_device_coherent(folio)) {
+ /*
+ * We always want a new GUP lookup with device coherent
+ * pages.
+ */
+ pages[i] = 0;
+ coherent_pages = true;
+
+ /*
+ * Migration will fail if the page is pinned, so convert
+ * the pin on the source page to a normal reference.
+ */
+ if (gup_flags & FOLL_PIN) {
+ get_page(&folio->page);
+ unpin_user_page(&folio->page);
+ }
+
+ ret = migrate_device_coherent_page(&folio->page);
+ if (ret)
+ goto unpin_pages;
+
continue;
+ }
+ if (folio_is_longterm_pinnable(folio))
+ continue;
/*
* Try to move out any movable page before pinning the range.
*/
@@ -1951,7 +1980,8 @@ static long check_and_migrate_movable_pages(unsigned long nr_pages,
folio_nr_pages(folio));
}
- if (!list_empty(&movable_page_list) || isolation_error_count)
+ if (!list_empty(&movable_page_list) || isolation_error_count
+ || coherent_pages)
goto unpin_pages;
/*
@@ -1961,10 +1991,16 @@ static long check_and_migrate_movable_pages(unsigned long nr_pages,
return nr_pages;
unpin_pages:
- if (gup_flags & FOLL_PIN) {
- unpin_user_pages(pages, nr_pages);
- } else {
- for (i = 0; i < nr_pages; i++)
+ /*
+ * pages[i] might be NULL if any device coherent pages were found.
+ */
+ for (i = 0; i < nr_pages; i++) {
+ if (!pages[i])
+ continue;
+
+ if (gup_flags & FOLL_PIN)
+ unpin_user_page(pages[i]);
+ else
put_page(pages[i]);
}
diff --git a/mm/internal.h b/mm/internal.h
index c0f8fbe0445b..899dab512c5a 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -853,6 +853,7 @@ int numa_migrate_prep(struct page *page, struct vm_area_struct *vma,
unsigned long addr, int page_nid, int *flags);
void free_zone_device_page(struct page *page);
+int migrate_device_coherent_page(struct page *page);
/*
* mm/gup.c
diff --git a/mm/migrate_device.c b/mm/migrate_device.c
index 18bc6483f63a..7feeb447e3b9 100644
--- a/mm/migrate_device.c
+++ b/mm/migrate_device.c
@@ -686,6 +686,12 @@ void migrate_vma_pages(struct migrate_vma *migrate)
}
if (!page) {
+ /*
+ * The only time there is no vma is when called from
+ * migrate_device_coherent_page(). However this isn't
+ * called if the page could not be unmapped.
+ */
+ VM_BUG_ON(!migrate->vma);
if (!(migrate->src[i] & MIGRATE_PFN_MIGRATE))
continue;
if (!notified) {
@@ -794,3 +800,49 @@ void migrate_vma_finalize(struct migrate_vma *migrate)
}
}
EXPORT_SYMBOL(migrate_vma_finalize);
+
+/*
+ * Migrate a device coherent page back to normal memory. The caller should have
+ * a reference on page which will be copied to the new page if migration is
+ * successful or dropped on failure.
+ */
+int migrate_device_coherent_page(struct page *page)
+{
+ unsigned long src_pfn, dst_pfn = 0;
+ struct migrate_vma args;
+ struct page *dpage;
+
+ WARN_ON_ONCE(PageCompound(page));
+
+ lock_page(page);
+ src_pfn = migrate_pfn(page_to_pfn(page)) | MIGRATE_PFN_MIGRATE;
+ args.src = &src_pfn;
+ args.dst = &dst_pfn;
+ args.cpages = 1;
+ args.npages = 1;
+ args.vma = NULL;
+
+ /*
+ * We don't have a VMA and don't need to walk the page tables to find
+ * the source page. So call migrate_vma_unmap() directly to unmap the
+ * page as migrate_vma_setup() will fail if args.vma == NULL.
+ */
+ migrate_vma_unmap(&args);
+ if (!(src_pfn & MIGRATE_PFN_MIGRATE))
+ return -EBUSY;
+
+ dpage = alloc_page(GFP_USER | __GFP_NOWARN);
+ if (dpage) {
+ lock_page(dpage);
+ dst_pfn = migrate_pfn(page_to_pfn(dpage));
+ }
+
+ migrate_vma_pages(&args);
+ if (src_pfn & MIGRATE_PFN_MIGRATE)
+ copy_highpage(dpage, page);
+ migrate_vma_finalize(&args);
+
+ if (src_pfn & MIGRATE_PFN_MIGRATE)
+ return 0;
+ return -EBUSY;
+}