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authorAlistair Popple <apopple@nvidia.com>2022-07-15 10:05:13 -0500
committerakpm <akpm@linux-foundation.org>2022-07-17 17:14:28 -0700
commitb05a79d4377f6dcc30683008ffd1c531ea965393 (patch)
tree4f491e0db9d5560f1f0a41bd0522938093f32a7c /mm/gup.c
parentdd19e6d8ffaa1289d75d7833de97faf1b6b2c8e4 (diff)
mm/gup: migrate device coherent pages when pinning instead of failing
Currently any attempts to pin a device coherent page will fail. This is because device coherent pages need to be managed by a device driver, and pinning them would prevent a driver from migrating them off the device. However this is no reason to fail pinning of these pages. These are coherent and accessible from the CPU so can be migrated just like pinning ZONE_MOVABLE pages. So instead of failing all attempts to pin them first try migrating them out of ZONE_DEVICE. [hch@lst.de: rebased to the split device memory checks, moved migrate_device_page to migrate_device.c] Link: https://lkml.kernel.org/r/20220715150521.18165-7-alex.sierra@amd.com Signed-off-by: Alistair Popple <apopple@nvidia.com> Signed-off-by: Christoph Hellwig <hch@lst.de> Acked-by: Felix Kuehling <Felix.Kuehling@amd.com> Cc: David Hildenbrand <david@redhat.com> Cc: Jason Gunthorpe <jgg@nvidia.com> Cc: Jerome Glisse <jglisse@redhat.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Ralph Campbell <rcampbell@nvidia.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm/gup.c')
-rw-r--r--mm/gup.c50
1 files changed, 43 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]);
}