[PATCH V3 6/4] 9p: fix new mount API cache option handling

[Eric Sandeen <sandeen@redhat.com>]

After commit 4eb3117888a92, 9p needs to be able to accept numerical
cache= mount options as well as the string "shortcuts" because the option
is printed numerically in /proc/mounts rather than by string. This was
missed in the mount API conversion, which used an enum for the shortcuts
and therefore could not handle a numeric equivalent as an argument
to the cache option.

Fix this by removing the enum and reverting to the slightly more
open-coded option handling for Opt_cache, with the reinstated
get_cache_mode() helper.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
---

If you wanted to fold this into my original mount api conversion patch
so there's no regression point, that would be fine with me as well,
of course. Sorry for the error.

diff --git a/fs/9p/v9fs.c b/fs/9p/v9fs.c
index d684cb406ed6..dea2c5347933 100644
--- a/fs/9p/v9fs.c
+++ b/fs/9p/v9fs.c
@@ -72,15 +72,6 @@ static const struct constant_table p9_versions[] = {
 	{}
 };
 
-static const struct constant_table p9_cache_mode[] = {
-	{ "loose",	CACHE_SC_LOOSE },
-	{ "fscache",	CACHE_SC_FSCACHE },
-	{ "mmap",	CACHE_SC_MMAP },
-	{ "readahead",	CACHE_SC_READAHEAD },
-	{ "none",	CACHE_SC_NONE },
-	{}
-};
-
 /*
  * This structure contains all parameters used for the core code,
  * the client, and all the transports.
@@ -97,7 +88,7 @@ const struct fs_parameter_spec v9fs_param_spec[] = {
 	fsparam_flag	("noxattr",	Opt_noxattr),
 	fsparam_flag	("directio",	Opt_directio),
 	fsparam_flag	("ignoreqv",	Opt_ignoreqv),
-	fsparam_enum	("cache",	Opt_cache, p9_cache_mode),
+	fsparam_string	("cache",	Opt_cache),
 	fsparam_string	("cachetag",	Opt_cachetag),
 	fsparam_string	("access",	Opt_access),
 	fsparam_flag	("posixacl",	Opt_posixacl),
@@ -124,6 +115,33 @@ const struct fs_parameter_spec v9fs_param_spec[] = {
 	{}
 };
 
+/* Interpret mount options for cache mode */
+static int get_cache_mode(char *s)
+{
+	int version = -EINVAL;
+
+	if (!strcmp(s, "loose")) {
+		version = CACHE_SC_LOOSE;
+		p9_debug(P9_DEBUG_9P, "Cache mode: loose\n");
+	} else if (!strcmp(s, "fscache")) {
+		version = CACHE_SC_FSCACHE;
+		p9_debug(P9_DEBUG_9P, "Cache mode: fscache\n");
+	} else if (!strcmp(s, "mmap")) {
+		version = CACHE_SC_MMAP;
+		p9_debug(P9_DEBUG_9P, "Cache mode: mmap\n");
+	} else if (!strcmp(s, "readahead")) {
+		version = CACHE_SC_READAHEAD;
+		p9_debug(P9_DEBUG_9P, "Cache mode: readahead\n");
+	} else if (!strcmp(s, "none")) {
+		version = CACHE_SC_NONE;
+		p9_debug(P9_DEBUG_9P, "Cache mode: none\n");
+	} else if (kstrtoint(s, 0, &version) != 0) {
+		version = -EINVAL;
+		pr_info("Unknown Cache mode or invalid value %s\n", s);
+	}
+	return version;
+}
+
 /*
  * Display the mount options in /proc/mounts.
  */
@@ -269,8 +287,10 @@ int v9fs_parse_param(struct fs_context *fc, struct fs_parameter *param)
 #endif
 		break;
 	case Opt_cache:
-		session_opts->cache = result.uint_32;
-		p9_debug(P9_DEBUG_9P, "Cache mode: %s\n", param->string);
+		r = get_cache_mode(param->string);
+		if (r < 0)
+			return r;
+		session_opts->cache = r;
 		break;
 	case Opt_access:
 		s = param->string;