@@ -1296,6 +1296,40 @@ int btrfs_quota_enable(struct btrfs_fs_info *fs_info,
return ret;
}
+/*
+ * It is possible to have outstanding ordered extents
+ * which reserved bytes before we disabled. We need to fully flush
+ * delalloc, ordered extents, and a commit to ensure that
+ * we don't leak such reservations, only to have them come back
+ * if we re-enable.
+ *
+ * i.e.:
+ * enable simple quotas
+ * reserve space
+ * release it, store rsv_bytes in OE
+ * disable quotas
+ * enable simple quotas (qgroup rsv are all 0)
+ * OE finishes
+ * run delayed refs
+ * free rsv_bytes, resulting in miscounting or even underflow
+ */
+static int flush_reservations(struct btrfs_fs_info *fs_info)
+{
+ struct btrfs_trans_handle *trans;
+ int ret;
+
+ ret = btrfs_start_delalloc_roots(fs_info, LONG_MAX, false);
+ if (ret)
+ return ret;
+ btrfs_wait_ordered_roots(fs_info, U64_MAX, 0, (u64)-1);
+ trans = btrfs_join_transaction(fs_info->tree_root);
+ if (IS_ERR(trans))
+ return PTR_ERR(trans);
+ btrfs_commit_transaction(trans);
+
+ return ret;
+}
+
int btrfs_quota_disable(struct btrfs_fs_info *fs_info)
{
struct btrfs_root *quota_root;
@@ -1340,6 +1374,10 @@ int btrfs_quota_disable(struct btrfs_fs_info *fs_info)
clear_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags);
btrfs_qgroup_wait_for_completion(fs_info, false);
+ ret = flush_reservations(fs_info);
+ if (ret)
+ goto out;
+
/*
* 1 For the root item
*
@@ -1401,7 +1439,7 @@ int btrfs_quota_disable(struct btrfs_fs_info *fs_info)
if (ret && trans)
btrfs_end_transaction(trans);
else if (trans)
- ret = btrfs_end_transaction(trans);
+ ret = btrfs_commit_transaction(trans);
mutex_unlock(&fs_info->cleaner_mutex);
return ret;
@@ -4021,8 +4059,11 @@ static int __btrfs_qgroup_release_data(struct btrfs_inode *inode,
int trace_op = QGROUP_RELEASE;
int ret;
- if (btrfs_qgroup_mode(inode->root->fs_info) == BTRFS_QGROUP_MODE_DISABLED)
- return 0;
+ if (btrfs_qgroup_mode(inode->root->fs_info) == BTRFS_QGROUP_MODE_DISABLED) {
+ extent_changeset_init(&changeset);
+ return clear_record_extent_bits(&inode->io_tree, start, start + len - 1,
+ EXTENT_QGROUP_RESERVED, &changeset);
+ }
/* In release case, we shouldn't have @reserved */
WARN_ON(!free && reserved);
The following sequence: enable simple quotas do some writes reserve space create ordered_extent release rsv (store rsv_bytes in OE, mark QGROUP_RESERVED bits) disable quotas enable simple quotas set qgroup rsv to 0 on all subvols ordered_extent finishes create delayed ref with rsv_bytes from before run delayed ref record_simple_quota_delta free rsv_bytes (0 -> -rsv_delta) results in us reliably underflowing the subvolume's qgroup rsv counter, because disabling/re-enabling quotas toggles reservation counters down to 0, but does not remove other file system state which represents successful acquisition of qgroup rsv space. Specifically metadata rsv counters on the root object and rsv_bytes on ordered_extent objects that have released their reservation as well as the corresponding QGROUP_RESERVED extent bits. Normal qgroups gets away with this, I believe because it forces more work to happen on transaction commit, but I am not certain it is totally safe from the ordered_extent/leaked extent bit variant. Simple quotas hits this reliably. The intent of the fix is to make disable take the time to clear that external to qgroups state as well: after flipping off the quota bit on fs_info, flush delalloc and ordered extents, clearing the extent bits along the way. This makes it so there are no ordered extents or meta prealloc hanging around from the first enablement period during the second. Signed-off-by: Boris Burkov <boris@bur.io> Reviewed-by: Josef Bacik <josef@toxicpanda.com> --- fs/btrfs/qgroup.c | 47 ++++++++++++++++++++++++++++++++++++++++++++--- 1 file changed, 44 insertions(+), 3 deletions(-)