mm: Fix missing folio invalidation calls during truncation

[ Upstream commit 0aa2e1b ]

When AS_RELEASE_ALWAYS is set on a mapping, the ->release_folio() and
->invalidate_folio() calls should be invoked even if PG_private and
PG_private_2 aren't set.  This is used by netfslib to keep track of the
point above which reads can be skipped in favour of just zeroing pagecache
locally.

There are a couple of places in truncation in which invalidation is only
called when folio_has_private() is true.  Fix these to check
folio_needs_release() instead.

Without this, the generic/075 and generic/112 xfstests (both fsx-based
tests) fail with minimum folio size patches applied[1].

Fixes: b4fa966 ("mm, netfs, fscache: stop read optimisation when folio removed from pagecache")
Signed-off-by: David Howells <[email protected]>
Link: https://lore.kernel.org/r/[email protected]/ [1]
Link: https://lore.kernel.org/r/[email protected]
Reviewed-by: Matthew Wilcox (Oracle) <[email protected]>
cc: Matthew Wilcox (Oracle) <[email protected]>
cc: Pankaj Raghav <[email protected]>
cc: Jeff Layton <[email protected]>
cc: Marc Dionne <[email protected]>
cc: [email protected]
cc: [email protected]
cc: [email protected]
cc: [email protected]
Signed-off-by: Christian Brauner <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>

mm/truncate.c

@@ -174,7 +174,7 @@ static void truncate_cleanup_folio(struct folio *folio)
 	if (folio_mapped(folio))
 		unmap_mapping_folio(folio);
 
-	if (folio_has_private(folio))
+	if (folio_needs_release(folio))
 		folio_invalidate(folio, 0, folio_size(folio));
 
 	/*
@@ -235,7 +235,7 @@ bool truncate_inode_partial_folio(struct folio *folio, loff_t start, loff_t end)
 	 */
 	folio_zero_range(folio, offset, length);
 
-	if (folio_has_private(folio))
+	if (folio_needs_release(folio))
 		folio_invalidate(folio, offset, length);
 	if (!folio_test_large(folio))
 		return true;