[PATCH 5/5] mm/hmm: WARN on illegal ->sync_cpu_device_pagetables errors

[Daniel Vetter]

Similar to the warning in the mmu notifer, warning if an hmm mirror
callback gets it's blocking vs. nonblocking handling wrong, or if it
fails with anything else than -EAGAIN.

Cc: Jason Gunthorpe <jgg@xxxxxxxx>
Cc: Ralph Campbell <rcampbell@xxxxxxxxxx>
Cc: John Hubbard <jhubbard@xxxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Balbir Singh <bsingharora@xxxxxxxxx>
Cc: Ira Weiny <ira.weiny@xxxxxxxxx>
Cc: Souptick Joarder <jrdr.linux@xxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: "JÃrÃme Glisse" <jglisse@xxxxxxxxxx>
Cc: linux-mm@xxxxxxxxx
Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxxx>
---
 mm/hmm.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/mm/hmm.c b/mm/hmm.c
index 16b6731a34db..52ac59384268 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -205,6 +205,9 @@ static int hmm_invalidate_range_start(struct mmu_notifier *mn,
 			ret = -EAGAIN;
 			break;
 		}
+		WARN(ret, "%pS callback failed with %d in %sblockable context\n",
+		     mirror->ops->sync_cpu_device_pagetables, ret,
+		     update.blockable ? "" : "non-");
 	}
 	up_read(&hmm->mirrors_sem);
 
-- 
2.22.0