Re: [PATCH v1 01/15] mm: add zone device coherent type memory support

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 




On 5/11/2022 9:58 PM, Alistair Popple wrote:
Alex Sierra <alex.sierra@xxxxxxx> writes:

[...]

diff --git a/mm/rmap.c b/mm/rmap.c
index fedb82371efe..d57102cd4b43 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1995,7 +1995,8 @@ void try_to_migrate(struct folio *folio, enum ttu_flags flags)
  					TTU_SYNC)))
  		return;

-	if (folio_is_zone_device(folio) && !folio_is_device_private(folio))
+	if (folio_is_zone_device(folio) &&
+	    (!folio_is_device_private(folio) && !folio_is_device_coherent(folio)))
  		return;

  	/*
I vaguely recall commenting on this previously, or at least intending
to. In try_to_migrate_one() we have this:

		if (folio_is_zone_device(folio)) {
			unsigned long pfn = folio_pfn(folio);
			swp_entry_t entry;
			pte_t swp_pte;

			/*
			 * Store the pfn of the page in a special migration
			 * pte. do_swap_page() will wait until the migration
			 * pte is removed and then restart fault handling.
			 */
			entry = pte_to_swp_entry(pteval);
			if (is_writable_device_private_entry(entry))
				entry = make_writable_migration_entry(pfn);
			else
				entry = make_readable_migration_entry(pfn);
			swp_pte = swp_entry_to_pte(entry);

The check in try_to_migrate() guarantees that if folio_is_zone_device()
is true this must be a DEVICE_PRIVATE page and it treats it as such by
assuming there is a special device private swap entry there.

Relying on that assumption seems bad, and I have no idea why I didn't
just use is_device_private_page() originally but I think the fix is just
to change this to:

		if (folio_is_device_private(folio))

Thanks Alistair. This worked fine. I'll drop patch 4 and update this patch in the next series version.

Regards,
Alex Sierra


And let DEVICE_COHERENT pages fall through to normal page processing.

  - Alistair



[Index of Archives]     [Reiser Filesystem Development]     [Ceph FS]     [Kernel Newbies]     [Security]     [Netfilter]     [Bugtraq]     [Linux FS]     [Yosemite National Park]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Samba]     [Device Mapper]     [Linux Media]

  Powered by Linux