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authorJosef Bacik <josef@toxicpanda.com>2020-03-04 17:18:24 +0100
committerDavid Sterba <dsterba@suse.com>2020-03-23 17:01:57 +0100
commit2abc726ab4b83db774e315c660ab8da21477092f (patch)
tree026a25254b297d0b984a33940c6475b1d1e7447c /fs/btrfs/relocation.c
parentbtrfs: reloc: clean dirty subvols if we fail to start a transaction (diff)
downloadlinux-2abc726ab4b83db774e315c660ab8da21477092f.tar.xz
linux-2abc726ab4b83db774e315c660ab8da21477092f.zip
btrfs: do not init a reloc root if we aren't relocating
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>
Diffstat (limited to '')
-rw-r--r--fs/btrfs/relocation.c20
1 files changed, 16 insertions, 4 deletions
diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index d2069d69fc92..631f94085ba6 100644
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -1511,6 +1511,10 @@ 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
@@ -1524,10 +1528,6 @@ 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;
@@ -2369,6 +2369,18 @@ 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;