Re: [PATCH RFC v6 3/5] mm/migrate: add copy offload registration infrastructure

[Huang, Ying]

Shivank Garg <shivankg@xxxxxxx> writes:

[snip]

> diff --git a/mm/migrate.c b/mm/migrate.c
> index 41b732e78a67..4fed3110ca0a 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -43,6 +43,7 @@
>  #include <linux/sched/sysctl.h>
>  #include <linux/memory-tiers.h>
>  #include <linux/pagewalk.h>
> +#include <linux/migrate_copy_offload.h>
>  
>  #include <asm/tlbflush.h>
>  
> @@ -51,12 +52,6 @@
>  #include "internal.h"
>  #include "swap.h"
>  
> -/* For now, never offload. Wired up in later patch. */
> -static bool migrate_should_offload(int reason)
> -{
> -	return false;
> -}
> -
>  static const struct movable_operations *offline_movable_ops;
>  static const struct movable_operations *zsmalloc_movable_ops;
>  
> @@ -2050,7 +2045,7 @@ static int migrate_pages_batch(struct list_head *from,
>  
>  	/* Batch-copy eligible folios before the move phase */
>  	if (!list_empty(&unmap_batch))
> -		migrate_folios_mc_copy(&dst_batch, &unmap_batch, nr_batch);
> +		migrate_offload_batch_copy(&dst_batch, &unmap_batch, nr_batch);
>  
>  	retry = 1;
>  	for (pass = 0; pass < nr_pass && retry; pass++) {

Found a difference between v5 and v6 here.  In v5, migrate_pages_batch()
checks the return value of migrate_offload_batch_copy() and acts
accordingly. While in v6, it does not.  Why was this changed?

IIUC, FOLIO_CONTENT_COPIED is now used to indicate a copy failure.  Is
this necessary?  Is it possible that some (but not all) folios fail to
be copied?

[snip]

---
Best Regards,
Huang, Ying