mm, virt: merge AS_UNMOVABLE and AS_INACCESSIBLE

The flags AS_UNMOVABLE and AS_INACCESSIBLE were both added just for guest_memfd;
AS_UNMOVABLE is already in existing versions of Linux, while AS_INACCESSIBLE was
acked for inclusion in 6.11.

But really, they are the same thing: only guest_memfd uses them, at least for
now, and guest_memfd pages are unmovable because they should not be
accessed by the CPU.

So merge them into one; use the AS_INACCESSIBLE name which is more comprehensive.
At the same time, this fixes an embarrassing bug where AS_INACCESSIBLE was used
as a bit mask, despite it being just a bit index.

The bug was mostly benign, because AS_INACCESSIBLE's bit representation (1010)
corresponded to setting AS_UNEVICTABLE (which is already set) and AS_ENOSPC
(except no async writes can happen on the guest_memfd).  So the AS_INACCESSIBLE
flag simply had no effect.

Fixes: 1d23040caa8b ("KVM: guest_memfd: Use AS_INACCESSIBLE when creating guest_memfd inode")
Fixes: c72ceafbd12c ("mm: Introduce AS_INACCESSIBLE for encrypted/confidential memory")
Cc: linux-mm@kvack.org
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: David Hildenbrand <david@redhat.com>
Tested-by: Michael Roth <michael.roth@amd.com>
Reviewed-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 6 insertions, 6 deletions

diff --git a/mm/compaction.c b/mm/compaction.c
index e731d45befc7..714afd9c6df6 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -1172,22 +1172,22 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
 		if (((mode & ISOLATE_ASYNC_MIGRATE) && is_dirty) ||
 		    (mapping && is_unevictable)) {
 			bool migrate_dirty = true;
-			bool is_unmovable;
+			bool is_inaccessible;
 
 			/*
 			 * Only folios without mappings or that have
 			 * a ->migrate_folio callback are possible to migrate
 			 * without blocking.
 			 *
-			 * Folios from unmovable mappings are not migratable.
+			 * Folios from inaccessible mappings are not migratable.
 			 *
 			 * However, we can be racing with truncation, which can
 			 * free the mapping that we need to check. Truncation
 			 * holds the folio lock until after the folio is removed
 			 * from the page so holding it ourselves is sufficient.
 			 *
-			 * To avoid locking the folio just to check unmovable,
-			 * assume every unmovable folio is also unevictable,
+			 * To avoid locking the folio just to check inaccessible,
+			 * assume every inaccessible folio is also unevictable,
 			 * which is a cheaper test.  If our assumption goes
 			 * wrong, it's not a correctness bug, just potentially
 			 * wasted cycles.
@@ -1200,9 +1200,9 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
 				migrate_dirty = !mapping ||
 						mapping->a_ops->migrate_folio;
 			}
-			is_unmovable = mapping && mapping_unmovable(mapping);
+			is_inaccessible = mapping && mapping_inaccessible(mapping);
 			folio_unlock(folio);
-			if (!migrate_dirty || is_unmovable)
+			if (!migrate_dirty || is_inaccessible)
 				goto isolate_fail_put;
 		}