btrfs: remove dead create_space_info calls

Since commit 2be12ef79 (btrfs: Separate space_info create/update), we've
separated out the creation and updating of the space info structures.
That commit was a straightforward refactoring of the two parts of
update_space_info, but we can go a step further.  Since commits
c59021f84 (Btrfs: fix OOPS of empty filesystem after balance) and
b742bb82f (Btrfs: Link block groups of different raid types), we know
that the space_info structures will be created at mount and there will
only ever be, at most, three of them.

This patch cleans out the create_space_info calls after __find_space_info
returns NULL since __find_space_info *can't* return NULL.

The initial cause for reviewing this was the kobject_add calls from
create_space_info occuring in sites where fs-reclaim wasn't allowed.  Now
we are certain they occur only early in the mount process and are safe.

Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 03be51d..ffa72ca 100644 (file)
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -954,9 +954,9 @@ struct btrfs_fs_info {
        struct btrfs_fs_devices *fs_devices;
 
        /*
-        * the space_info list is almost entirely read only.  It only changes
-        * when we add a new raid type to the FS, and that happens
-        * very rarely.  RCU is used to protect it.
+        * The space_info list is effectively read only after initial
+        * setup.  It is populated at mount time and cleaned up after
+        * all block groups are removed.  RCU is used to protect it.
         */
        struct list_head space_info;
 

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 1b54d9a..e10f74d 100644 (file)
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -4606,11 +4606,7 @@ static int do_chunk_alloc(struct btrfs_trans_handle *trans,
                return -ENOSPC;
 
        space_info = __find_space_info(fs_info, flags);
-       if (!space_info) {
-               ret = create_space_info(fs_info, flags, &space_info);
-               if (ret)
-                       return ret;
-       }
+       ASSERT(space_info);
 
 again:
        spin_lock(&space_info->lock);
@@ -10265,15 +10261,7 @@ int btrfs_make_block_group(struct btrfs_trans_handle *trans,
         * with its ->space_info set.
         */
        cache->space_info = __find_space_info(fs_info, cache->flags);
-       if (!cache->space_info) {
-               ret = create_space_info(fs_info, cache->flags,
-                                      &cache->space_info);
-               if (ret) {
-                       btrfs_remove_free_space_cache(cache);
-                       btrfs_put_block_group(cache);
-                       return ret;
-               }
-       }
+       ASSERT(cache->space_info);
 
        ret = btrfs_add_block_group_cache(fs_info, cache);
        if (ret) {