fs/9p: Rework cache modes and add new options to Documentation

Switch cache modes to a bit-mask and use legacy
cache names as shortcuts.  Update documentation to
include information on both shortcuts and bitmasks.

This patch also fixes missing guards related to fscache.

Update the documentation for new mount flags
and cache modes.

Signed-off-by: Eric Van Hensbergen <ericvh@kernel.org>

1 files changed, 43 insertions, 24 deletions

diff --git a/fs/9p/v9fs.h b/fs/9p/v9fs.h
index 999cdbcbfed9..06a2514f0d88 100644
--- a/fs/9p/v9fs.h
+++ b/fs/9p/v9fs.h
@@ -31,35 +31,54 @@
 #define V9FS_ACL_MASK V9FS_POSIX_ACL
 
 enum p9_session_flags {
-	V9FS_PROTO_2000U	= 0x01,
-	V9FS_PROTO_2000L	= 0x02,
-	V9FS_ACCESS_SINGLE	= 0x04,
-	V9FS_ACCESS_USER	= 0x08,
-	V9FS_ACCESS_CLIENT	= 0x10,
-	V9FS_POSIX_ACL		= 0x20,
-	V9FS_NO_XATTR		= 0x40,
-	V9FS_IGNORE_QV		= 0x80, /* ignore qid.version for cache hints */
-	V9FS_DIRECT_IO		= 0x100,
-	V9FS_SYNC		= 0x200
+	V9FS_PROTO_2000U    = 0x01,
+	V9FS_PROTO_2000L    = 0x02,
+	V9FS_ACCESS_SINGLE  = 0x04,
+	V9FS_ACCESS_USER    = 0x08,
+	V9FS_ACCESS_CLIENT  = 0x10,
+	V9FS_POSIX_ACL      = 0x20,
+	V9FS_NO_XATTR       = 0x40,
+	V9FS_IGNORE_QV      = 0x80, /* ignore qid.version for cache hints */
+	V9FS_DIRECT_IO      = 0x100,
+	V9FS_SYNC           = 0x200
 };
 
-/* possible values of ->cache */
 /**
- * enum p9_cache_modes - user specified cache preferences
- * @CACHE_NONE: do not cache data, dentries, or directory contents (default)
- * @CACHE_LOOSE: cache data, dentries, and directory contents w/no consistency
+ * enum p9_cache_shortcuts - human readable cache preferences
+ * @CACHE_SC_NONE: disable all caches
+ * @CACHE_SC_READAHEAD: only provide caching for readahead
+ * @CACHE_SC_MMAP: provide caching to enable mmap
+ * @CACHE_SC_LOOSE: non-coherent caching for files and meta data
+ * @CACHE_SC_FSCACHE: persistent non-coherent caching for files and meta-data
  *
- * eventually support loose, tight, time, session, default always none
  */
 
-enum p9_cache_modes {
-	CACHE_NONE,
-	CACHE_READAHEAD,
-	CACHE_WRITEBACK,
-	CACHE_MMAP,
-	CACHE_LOOSE,
-	CACHE_FSCACHE,
-	nr__p9_cache_modes
+enum p9_cache_shortcuts {
+	CACHE_SC_NONE       = 0b00000000,
+	CACHE_SC_READAHEAD  = 0b00000001,
+	CACHE_SC_MMAP       = 0b00000101,
+	CACHE_SC_LOOSE      = 0b00001111,
+	CACHE_SC_FSCACHE    = 0b10001111,
+};
+
+/**
+ * enum p9_cache_bits - possible values of ->cache
+ * @CACHE_NONE: caches disabled
+ * @CACHE_FILE: file caching (open to close)
+ * @CACHE_META: meta-data and directory caching
+ * @CACHE_WRITEBACK: write-back caching for files
+ * @CACHE_LOOSE: don't check cache consistency
+ * @CACHE_FSCACHE: local persistent caches
+ *
+ */
+
+enum p9_cache_bits {
+	CACHE_NONE          = 0b00000000,
+	CACHE_FILE          = 0b00000001,
+	CACHE_META          = 0b00000010,
+	CACHE_WRITEBACK     = 0b00000100,
+	CACHE_LOOSE         = 0b00001000,
+	CACHE_FSCACHE       = 0b10000000,
 };
 
 /**
@@ -68,7 +87,7 @@ enum p9_cache_modes {
  * @nodev: set to 1 to disable device mapping
  * @debug: debug level
  * @afid: authentication handle
- * @cache: cache mode of type &p9_cache_modes
+ * @cache: cache mode of type &p9_cache_bits
  * @cachetag: the tag of the cache associated with this session
  * @fscache: session cookie associated with FS-Cache
  * @uname: string user name to mount hierarchy as