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>

1 files changed, 15 insertions, 4 deletions

diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c
index ce14a3d1f609..44df244807e5 100644
--- 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;
 }