v4.19.13 snapshot.
diff --git a/include/linux/cleancache.h b/include/linux/cleancache.h
new file mode 100644
index 0000000..5f5730c
--- /dev/null
+++ b/include/linux/cleancache.h
@@ -0,0 +1,124 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_CLEANCACHE_H
+#define _LINUX_CLEANCACHE_H
+
+#include <linux/fs.h>
+#include <linux/exportfs.h>
+#include <linux/mm.h>
+
+#define CLEANCACHE_NO_POOL -1
+#define CLEANCACHE_NO_BACKEND -2
+#define CLEANCACHE_NO_BACKEND_SHARED -3
+
+#define CLEANCACHE_KEY_MAX 6
+
+/*
+ * cleancache requires every file with a page in cleancache to have a
+ * unique key unless/until the file is removed/truncated. For some
+ * filesystems, the inode number is unique, but for "modern" filesystems
+ * an exportable filehandle is required (see exportfs.h)
+ */
+struct cleancache_filekey {
+ union {
+ ino_t ino;
+ __u32 fh[CLEANCACHE_KEY_MAX];
+ u32 key[CLEANCACHE_KEY_MAX];
+ } u;
+};
+
+struct cleancache_ops {
+ int (*init_fs)(size_t);
+ int (*init_shared_fs)(uuid_t *uuid, size_t);
+ int (*get_page)(int, struct cleancache_filekey,
+ pgoff_t, struct page *);
+ void (*put_page)(int, struct cleancache_filekey,
+ pgoff_t, struct page *);
+ void (*invalidate_page)(int, struct cleancache_filekey, pgoff_t);
+ void (*invalidate_inode)(int, struct cleancache_filekey);
+ void (*invalidate_fs)(int);
+};
+
+extern int cleancache_register_ops(const struct cleancache_ops *ops);
+extern void __cleancache_init_fs(struct super_block *);
+extern void __cleancache_init_shared_fs(struct super_block *);
+extern int __cleancache_get_page(struct page *);
+extern void __cleancache_put_page(struct page *);
+extern void __cleancache_invalidate_page(struct address_space *, struct page *);
+extern void __cleancache_invalidate_inode(struct address_space *);
+extern void __cleancache_invalidate_fs(struct super_block *);
+
+#ifdef CONFIG_CLEANCACHE
+#define cleancache_enabled (1)
+static inline bool cleancache_fs_enabled_mapping(struct address_space *mapping)
+{
+ return mapping->host->i_sb->cleancache_poolid >= 0;
+}
+static inline bool cleancache_fs_enabled(struct page *page)
+{
+ return cleancache_fs_enabled_mapping(page->mapping);
+}
+#else
+#define cleancache_enabled (0)
+#define cleancache_fs_enabled(_page) (0)
+#define cleancache_fs_enabled_mapping(_page) (0)
+#endif
+
+/*
+ * The shim layer provided by these inline functions allows the compiler
+ * to reduce all cleancache hooks to nothingness if CONFIG_CLEANCACHE
+ * is disabled, to a single global variable check if CONFIG_CLEANCACHE
+ * is enabled but no cleancache "backend" has dynamically enabled it,
+ * and, for the most frequent cleancache ops, to a single global variable
+ * check plus a superblock element comparison if CONFIG_CLEANCACHE is enabled
+ * and a cleancache backend has dynamically enabled cleancache, but the
+ * filesystem referenced by that cleancache op has not enabled cleancache.
+ * As a result, CONFIG_CLEANCACHE can be enabled by default with essentially
+ * no measurable performance impact.
+ */
+
+static inline void cleancache_init_fs(struct super_block *sb)
+{
+ if (cleancache_enabled)
+ __cleancache_init_fs(sb);
+}
+
+static inline void cleancache_init_shared_fs(struct super_block *sb)
+{
+ if (cleancache_enabled)
+ __cleancache_init_shared_fs(sb);
+}
+
+static inline int cleancache_get_page(struct page *page)
+{
+ if (cleancache_enabled && cleancache_fs_enabled(page))
+ return __cleancache_get_page(page);
+ return -1;
+}
+
+static inline void cleancache_put_page(struct page *page)
+{
+ if (cleancache_enabled && cleancache_fs_enabled(page))
+ __cleancache_put_page(page);
+}
+
+static inline void cleancache_invalidate_page(struct address_space *mapping,
+ struct page *page)
+{
+ /* careful... page->mapping is NULL sometimes when this is called */
+ if (cleancache_enabled && cleancache_fs_enabled_mapping(mapping))
+ __cleancache_invalidate_page(mapping, page);
+}
+
+static inline void cleancache_invalidate_inode(struct address_space *mapping)
+{
+ if (cleancache_enabled && cleancache_fs_enabled_mapping(mapping))
+ __cleancache_invalidate_inode(mapping);
+}
+
+static inline void cleancache_invalidate_fs(struct super_block *sb)
+{
+ if (cleancache_enabled)
+ __cleancache_invalidate_fs(sb);
+}
+
+#endif /* _LINUX_CLEANCACHE_H */