mm: cleancache core ops functions and config
This third patch of eight in this cleancache series provides
the core code for cleancache that interfaces between the hooks in
VFS and individual filesystems and a cleancache backend. It also
includes build and config patches.
Two new files are added: mm/cleancache.c and include/linux/cleancache.h.
Note that CONFIG_CLEANCACHE can default to on; in systems that do
not provide a cleancache backend, all hooks devolve to a simple
check of a global enable flag, so performance impact should
be negligible but can be reduced to zero impact if config'ed off.
However for this first commit, it defaults to off.
Details and a FAQ can be found in Documentation/vm/cleancache.txt
Credits: Cleancache_ops design derived from Jeremy Fitzhardinge
design for tmem
[v8: [email protected]: fix exportfs call affecting btrfs]
[v8: [email protected]: use static inline function, not macro]
[v7: [email protected]: cleanup sysfs and remove cleancache prefix]
[v6: [email protected]: robustly handle buggy fs encode_fh actor definition]
[v5: [email protected]: clean up global usage and static var names]
[v5: [email protected]: simplify init hook and any future fs init changes]
[v5: [email protected]: cleaner non-global interface for ops registration]
[v4: [email protected]: interface must support exportfs FS's]
[v4: [email protected]: interface must support 64-bit FS on 32-bit kernel]
[v3: [email protected]: use one ops struct to avoid pointer hops]
[v3: [email protected]: document and ensure PageLocked reqts are met]
[v3: [email protected]: fix success/fail codes, change funcs to void]
[v2: [email protected]: use sane types]
Signed-off-by: Dan Magenheimer <[email protected]>
Reviewed-by: Jeremy Fitzhardinge <[email protected]>
Reviewed-by: Konrad Rzeszutek Wilk <[email protected]>
Acked-by: Al Viro <[email protected]>
Acked-by: Andrew Morton <[email protected]>
Acked-by: Nitin Gupta <[email protected]>
Acked-by: Minchan Kim <[email protected]>
Acked-by: Andreas Dilger <[email protected]>
Acked-by: Jan Beulich <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Nick Piggin <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Rik Van Riel <[email protected]>
Cc: Chris Mason <[email protected]>
Cc: Ted Ts'o <[email protected]>
Cc: Mark Fasheh <[email protected]>
Cc: Joel Becker <[email protected]>
diff --git a/include/linux/cleancache.h b/include/linux/cleancache.h
new file mode 100644
index 0000000..04ffb2e
--- /dev/null
+++ b/include/linux/cleancache.h
@@ -0,0 +1,122 @@
+#ifndef _LINUX_CLEANCACHE_H
+#define _LINUX_CLEANCACHE_H
+
+#include <linux/fs.h>
+#include <linux/exportfs.h>
+#include <linux/mm.h>
+
+#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)(char *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 (*flush_page)(int, struct cleancache_filekey, pgoff_t);
+ void (*flush_inode)(int, struct cleancache_filekey);
+ void (*flush_fs)(int);
+};
+
+extern struct cleancache_ops
+ cleancache_register_ops(struct cleancache_ops *ops);
+extern void __cleancache_init_fs(struct super_block *);
+extern void __cleancache_init_shared_fs(char *, struct super_block *);
+extern int __cleancache_get_page(struct page *);
+extern void __cleancache_put_page(struct page *);
+extern void __cleancache_flush_page(struct address_space *, struct page *);
+extern void __cleancache_flush_inode(struct address_space *);
+extern void __cleancache_flush_fs(struct super_block *);
+extern int cleancache_enabled;
+
+#ifdef CONFIG_CLEANCACHE
+static inline bool cleancache_fs_enabled(struct page *page)
+{
+ return page->mapping->host->i_sb->cleancache_poolid >= 0;
+}
+static inline bool cleancache_fs_enabled_mapping(struct address_space *mapping)
+{
+ return mapping->host->i_sb->cleancache_poolid >= 0;
+}
+#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(char *uuid, struct super_block *sb)
+{
+ if (cleancache_enabled)
+ __cleancache_init_shared_fs(uuid, sb);
+}
+
+static inline int cleancache_get_page(struct page *page)
+{
+ int ret = -1;
+
+ if (cleancache_enabled && cleancache_fs_enabled(page))
+ ret = __cleancache_get_page(page);
+ return ret;
+}
+
+static inline void cleancache_put_page(struct page *page)
+{
+ if (cleancache_enabled && cleancache_fs_enabled(page))
+ __cleancache_put_page(page);
+}
+
+static inline void cleancache_flush_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_flush_page(mapping, page);
+}
+
+static inline void cleancache_flush_inode(struct address_space *mapping)
+{
+ if (cleancache_enabled && cleancache_fs_enabled_mapping(mapping))
+ __cleancache_flush_inode(mapping);
+}
+
+static inline void cleancache_flush_fs(struct super_block *sb)
+{
+ if (cleancache_enabled)
+ __cleancache_flush_fs(sb);
+}
+
+#endif /* _LINUX_CLEANCACHE_H */
