From: Josef Bacik josef@toxicpanda.com
[ Upstream commit 2abc726ab4b83db774e315c660ab8da21477092f ]
We previously were checking if the root had a dead root before accessing root->reloc_root in order to avoid a use-after-free type bug. However this scenario happens after we've unset the reloc control, so we would have been saved if we'd simply checked for fs_info->reloc_control. At this point during relocation we no longer need to be creating new reloc roots, so simply move this check above the reloc_root checks to avoid any future races and confusion.
Reviewed-by: Qu Wenruo wqu@suse.com Signed-off-by: Josef Bacik josef@toxicpanda.com Reviewed-by: David Sterba dsterba@suse.com Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Sasha Levin sashal@kernel.org --- fs/btrfs/relocation.c | 20 ++++++++++++++++---- 1 file changed, 16 insertions(+), 4 deletions(-)
diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c index af3605a0bf2e0..1313506a7ecb5 100644 --- a/fs/btrfs/relocation.c +++ b/fs/btrfs/relocation.c @@ -1468,6 +1468,10 @@ int btrfs_init_reloc_root(struct btrfs_trans_handle *trans, int clear_rsv = 0; int ret;
+ if (!rc || !rc->create_reloc_tree || + root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID) + return 0; + /* * The subvolume has reloc tree but the swap is finished, no need to * create/update the dead reloc tree @@ -1481,10 +1485,6 @@ int btrfs_init_reloc_root(struct btrfs_trans_handle *trans, return 0; }
- if (!rc || !rc->create_reloc_tree || - root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID) - return 0; - if (!trans->reloc_reserved) { rsv = trans->block_rsv; trans->block_rsv = rc->block_rsv; @@ -2336,6 +2336,18 @@ static noinline_for_stack int merge_reloc_root(struct reloc_control *rc, trans = NULL; goto out; } + + /* + * At this point we no longer have a reloc_control, so we can't + * depend on btrfs_init_reloc_root to update our last_trans. + * + * But that's ok, we started the trans handle on our + * corresponding fs_root, which means it's been added to the + * dirty list. At commit time we'll still call + * btrfs_update_reloc_root() and update our root item + * appropriately. + */ + reloc_root->last_trans = trans->transid; trans->block_rsv = rc->block_rsv;
replaced = 0;