ARM: 9480/1: entry: expand comment in __switch_tografted

As per discussion between the developers in the mail thread
linked, expand the comment in __switch_to so that readers
of the code understand what is going on.

Suggested-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Linus Walleij <linusw@kernel.org>>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

1 files changed, 58 insertions, 0 deletions

diff --git a/fs/verity/pagecache.c b/fs/verity/pagecache.c
new file mode 100644
index 000000000..1819314ec
--- /dev/null
+++ b/fs/verity/pagecache.c
@@ -0,0 +1,58 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright 2019 Google LLC
+ */
+
+#include <linux/export.h>
+#include <linux/fsverity.h>
+#include <linux/pagemap.h>
+
+/**
+ * generic_read_merkle_tree_page - generic ->read_merkle_tree_page helper
+ * @inode:	inode containing the Merkle tree
+ * @index:	0-based index of the Merkle tree page in the inode
+ *
+ * The caller needs to adjust @index from the Merkle-tree relative index passed
+ * to ->read_merkle_tree_page to the actual index where the Merkle tree is
+ * stored in the page cache for @inode.
+ */
+struct page *generic_read_merkle_tree_page(struct inode *inode, pgoff_t index)
+{
+	struct folio *folio;
+
+	folio = read_mapping_folio(inode->i_mapping, index, NULL);
+	if (IS_ERR(folio))
+		return ERR_CAST(folio);
+	return folio_file_page(folio, index);
+}
+EXPORT_SYMBOL_GPL(generic_read_merkle_tree_page);
+
+/**
+ * generic_readahead_merkle_tree() - generic ->readahead_merkle_tree helper
+ * @inode:	inode containing the Merkle tree
+ * @index:	0-based index of the first Merkle tree page to read ahead in the
+ *		inode
+ * @nr_pages:	the number of Merkle tree pages that should be read ahead
+ *
+ * The caller needs to adjust @index from the Merkle-tree relative index passed
+ * to ->read_merkle_tree_page to the actual index where the Merkle tree is
+ * stored in the page cache for @inode.
+ */
+void generic_readahead_merkle_tree(struct inode *inode, pgoff_t index,
+				   unsigned long nr_pages)
+{
+	struct folio *folio;
+
+	lockdep_assert_held(&inode->i_mapping->invalidate_lock);
+
+	folio = __filemap_get_folio(inode->i_mapping, index, FGP_ACCESSED, 0);
+	if (folio == ERR_PTR(-ENOENT) ||
+	    (!IS_ERR(folio) && !folio_test_uptodate(folio))) {
+		DEFINE_READAHEAD(ractl, NULL, NULL, inode->i_mapping, index);
+
+		page_cache_ra_unbounded(&ractl, nr_pages, 0);
+	}
+	if (!IS_ERR(folio))
+		folio_put(folio);
+}
+EXPORT_SYMBOL_GPL(generic_readahead_merkle_tree);