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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>
This commit is contained in:
Jeff Mahoney 2018-03-20 15:25:25 -04:00 committed by David Sterba
parent 580c6efaf9
commit dc2d3005d2
2 changed files with 5 additions and 17 deletions
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6
fs/btrfs/ctree.h
View File

@ -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;

16
fs/btrfs/extent-tree.c
View File

@ -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) {