dm cache: only allow a single io_mode cache feature to be requested

More than one io_mode feature can be requested when creating a dm cache
device (as is: last one wins).  The io_mode selections are incompatible
with one another, we should force them to be selected exclusively.  Add
a counter to check for more than one io_mode selection.

Fixes: 629d0a8a1a10 ("dm cache metadata: add "metadata2" feature")
Signed-off-by: John Pittman <jpittman@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c
index ce14a3d1f609dfe127f6caff75c3a00a6d99254a..44df244807e5a0ae0aa8db3d0962827623711780 100644 (file)
--- a/drivers/md/dm-cache-target.c
+++ b/drivers/md/dm-cache-target.c
@@ -2250,7 +2250,7 @@ static int parse_features(struct cache_args *ca, struct dm_arg_set *as,
                {0, 2, "Invalid number of cache feature arguments"},
        };
 
-       int r;
+       int r, mode_ctr = 0;
        unsigned argc;
        const char *arg;
        struct cache_features *cf = &ca->features;
@@ -2264,14 +2264,20 @@ static int parse_features(struct cache_args *ca, struct dm_arg_set *as,
        while (argc--) {
                arg = dm_shift_arg(as);
 
-               if (!strcasecmp(arg, "writeback"))
+               if (!strcasecmp(arg, "writeback")) {
                        cf->io_mode = CM_IO_WRITEBACK;
+                       mode_ctr++;
+               }
 
-               else if (!strcasecmp(arg, "writethrough"))
+               else if (!strcasecmp(arg, "writethrough")) {
                        cf->io_mode = CM_IO_WRITETHROUGH;
+                       mode_ctr++;
+               }
 
-               else if (!strcasecmp(arg, "passthrough"))
+               else if (!strcasecmp(arg, "passthrough")) {
                        cf->io_mode = CM_IO_PASSTHROUGH;
+                       mode_ctr++;
+               }
 
                else if (!strcasecmp(arg, "metadata2"))
                        cf->metadata_version = 2;
@@ -2282,6 +2288,11 @@ static int parse_features(struct cache_args *ca, struct dm_arg_set *as,
                }
        }
 
+       if (mode_ctr > 1) {
+               *error = "Duplicate cache io_mode features requested";
+               return -EINVAL;
+       }
+
        return 0;
 }