bcache: Warn when a device is already registered.

Signed-off-by: Gabriel de Perthuis <g2p.code+bcache@gmail.com>
Signed-off-by: Kent Overstreet <koverstreet@google.com>

diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index f88e2b6..3de5626 100644 (file)
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -1786,6 +1786,36 @@ static ssize_t register_bcache(struct kobject *, struct kobj_attribute *,
 kobj_attribute_write(register,         register_bcache);
 kobj_attribute_write(register_quiet,   register_bcache);
 
+static bool bch_is_open_backing(struct block_device *bdev) {
+       struct cache_set *c, *tc;
+       struct cached_dev *dc, *t;
+
+       list_for_each_entry_safe(c, tc, &bch_cache_sets, list)
+               list_for_each_entry_safe(dc, t, &c->cached_devs, list)
+                       if (dc->bdev == bdev)
+                               return true;
+       list_for_each_entry_safe(dc, t, &uncached_devices, list)
+               if (dc->bdev == bdev)
+                       return true;
+       return false;
+}
+
+static bool bch_is_open_cache(struct block_device *bdev) {
+       struct cache_set *c, *tc;
+       struct cache *ca;
+       unsigned i;
+
+       list_for_each_entry_safe(c, tc, &bch_cache_sets, list)
+               for_each_cache(ca, c, i)
+                       if (ca->bdev == bdev)
+                               return true;
+       return false;
+}
+
+static bool bch_is_open(struct block_device *bdev) {
+       return bch_is_open_cache(bdev) || bch_is_open_backing(bdev);
+}
+
 static ssize_t register_bcache(struct kobject *k, struct kobj_attribute *attr,
                               const char *buffer, size_t size)
 {
@@ -1810,8 +1840,13 @@ static ssize_t register_bcache(struct kobject *k, struct kobj_attribute *attr,
                                  FMODE_READ|FMODE_WRITE|FMODE_EXCL,
                                  sb);
        if (IS_ERR(bdev)) {
-               if (bdev == ERR_PTR(-EBUSY))
-                       err = "device busy";
+               if (bdev == ERR_PTR(-EBUSY)) {
+                       bdev = lookup_bdev(strim(path));
+                       if (!IS_ERR(bdev) && bch_is_open(bdev))
+                               err = "device already registered";
+                       else
+                               err = "device busy";
+               }
                goto err;
        }