btrfs: allocate raid type kobjects dynamically

We are currently allocating space_info objects in an array when we
allocate space_info. When a user does something like:

# btrfs balance start -mconvert=raid1 -dconvert=raid1 /mnt
# btrfs balance start -mconvert=single -dconvert=single /mnt -f
# btrfs balance start -mconvert=raid1 -dconvert=raid1 /

We can end up with memory corruption since the kobject hasn't
been reinitialized properly and the name pointer was left set.

The rationale behind allocating them statically was to avoid
creating a separate kobject container that just contained the
raid type. It used the index in the array to determine the index.

Ultimately, though, this wastes more memory than it saves in all
but the most complex scenarios and introduces kobject lifetime
questions.

This patch allocates the kobjects dynamically instead. Note that
we also remove the kobject_get/put of the parent kobject since
kobject_add and kobject_del do that internally.

Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Reported-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Chris Mason <clm@fb.com>

1 files changed, 7 insertions, 1 deletions

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 02895a126ab9..af523d695432 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1123,6 +1123,12 @@ struct btrfs_qgroup_limit_item {
         __le64 rsv_excl;
 } __attribute__ ((__packed__));
 
+/* For raid type sysfs entries */
+struct raid_kobject {
+        int raid_type;
+        struct kobject kobj;
+};
+
 struct btrfs_space_info {
         spinlock_t lock;
 
@@ -1173,7 +1179,7 @@ struct btrfs_space_info {
         wait_queue_head_t wait;
 
         struct kobject kobj;
-        struct kobject block_group_kobjs[BTRFS_NR_RAID_TYPES];
+        struct kobject *block_group_kobjs[BTRFS_NR_RAID_TYPES];
 };
 
 #define BTRFS_BLOCK_RSV_GLOBAL          1