On Thursday, 27 January 2022 2:09:42 PM AEDT Alex Sierra wrote:
Avoid long term pinning for Coherent device type pages. This could interfere with their own device memory manager. For now, we are just returning error for PIN_LONGTERM Coherent device type pages. Eventually, these type of pages will get migrated to system memory, once the device migration pages support is added.
Signed-off-by: Alex Sierra alex.sierra@amd.com
mm/gup.c | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/mm/gup.c b/mm/gup.c index 886d6148d3d0..5291d7221826 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -1720,6 +1720,12 @@ static long check_and_migrate_movable_pages(unsigned long nr_pages, * If we get a movable page, since we are going to be pinning * these entries, try to move them out if possible. */
if (is_dev_private_or_coherent_page(head)) {WARN_ON_ONCE(is_device_private_page(head));ret = -EFAULT;goto unpin_pages;}- if (!is_pinnable_page(head)) { if (PageHuge(head)) { if (!isolate_huge_page(head, &movable_page_list))
@@ -1750,6 +1756,7 @@ static long check_and_migrate_movable_pages(unsigned long nr_pages, if (list_empty(&movable_page_list) && !isolation_error_count) return nr_pages;
+unpin_pages: if (gup_flags & FOLL_PIN) { unpin_user_pages(pages, nr_pages); } else {
If there is a mix of ZONE_MOVABLE and device pages the return value (ret) will be subsequently lost here:
if (!list_empty(&movable_page_list)) { ret = migrate_pages(&movable_page_list, alloc_migration_target, NULL, (unsigned long)&mtc, MIGRATE_SYNC, MR_LONGTERM_PIN, NULL); if (ret && !list_empty(&movable_page_list)) putback_movable_pages(&movable_page_list); }
Which won't actually cause any problems, but it will lead to the GUP getting retried unnecessarily. I do still intend to address this with a series to migrate pages instead though, so I think this is ok for now as it's an unlikely corner case anyway. Therefore feel tree to add the below when you repost:
Reviewed-by: Alistair Poppple apopple@nvidia.com