This fixes commit 54d516b1d62f ("mm/gup: small refactoring: simplify
try_grab_page()") which refactors try_grab_page() to call
try_grab_compound_head() with refs=1. The refactor commit is causing
pin_user_pages() to return -ENOMEM when we try to pin one user page that
is migratable and not in the movable zone. Previously, try_grab_page()
didn't check if the page was pinnable for FOLL_PIN. To match the same
functionality, this fix adds the check `refs > 1 &&` to skip the call to
is_pinnable_page().
This issue is reproducible with the Pixel 6 on the 5.15 LTS kernel. Here
is the call stack to reproduce the -ENOMEM error:
Call trace:
: dump_backtrace.cfi_jt+0x0/0x8
: show_stack+0x1c/0x2c
: dump_stack_lvl+0x68/0x98
: try_grab_compound_head+0x298/0x3c4
: follow_page_pte+0x1dc/0x330
: follow_page_mask+0x174/0x340
: __get_user_pages+0x158/0x34c
: __gup_longterm_locked+0xfc/0x194
: __gup_longterm_unlocked+0x80/0xf4
: internal_get_user_pages_fast+0xf0/0x15c
: pin_user_pages_fast+0x24/0x40
: edgetpu_device_group_map+0x130/0x584 [abrolhos]
: edgetpu_ioctl_map_buffer+0x110/0x3b4 [abrolhos]
: edgetpu_ioctl+0x238/0x408 [abrolhos]
: edgetpu_fs_ioctl+0x14/0x24 [abrolhos]
Fixes: 54d516b1d62f ("mm/gup: small refactoring: simplify try_grab_page()")
Cc: John Hubbard <jhubbard@xxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Signed-off-by: Will McVicker <willmcvicker@xxxxxxxxxx>
---
mm/gup.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/gup.c b/mm/gup.c
index f0af462ac1e2..0509c49c46a3 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -135,7 +135,7 @@ struct page *try_grab_compound_head(struct page *page,
* right zone, so fail and let the caller fall back to the slow
* path.
*/
- if (unlikely((flags & FOLL_LONGTERM) &&
+ if (refs > 1 && unlikely((flags & FOLL_LONGTERM) &&
!is_pinnable_page(page)))
return NULL;
--
2.35.0.rc2.247.g8bbb082509-goog
