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IFF a blind retry is all that is needed it >>> should be done in the core functionality. I fear it's not that easy, >>> though. >> >> +1 >> >> This migration retry weirdness is a GUP issue, it needs to be solved >> in the mm not exposed to every pin_user_pages caller. >> >> If it turns out ZONE_MOVEABLE pages can't actually be reliably moved >> then it is pretty broken.. > > I wonder if we should remove the arbitrary retry limit in > migrate_pages() entirely for ZONE_MOVEABLE pages and just loop until > they migrate? By definition there should only be transient references on > these pages so why do we need to limit the number of retries in the > first place? > Well, along those lines, I can confirm that this patch also fixes the symptoms: diff --git a/mm/migrate.c b/mm/migrate.c index 73a052a382f1..faa67cc441e2 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -1728,7 +1728,9 @@ static int migrate_pages_batch(struct list_head *from, else goto move; case -EAGAIN: - retry++; + /* For ZONE_MOVABLE folios, retry forever */ + if (!folio_is_zone_movable(folio)) + retry++; thp_retry += is_thp; nr_retry_pages += nr_pages; break; @@ -1786,7 +1788,9 @@ static int migrate_pages_batch(struct list_head *from, */ switch(rc) { case -EAGAIN: - retry++; + /* For ZONE_MOVABLE folios, retry forever */ + if (!folio_is_zone_movable(folio)) + retry++; thp_retry += is_thp; nr_retry_pages += nr_pages; break; thanks, -- John Hubbard NVIDIA