From 08530d6e638427e7e1344bd67bacc03882ba95b9 Mon Sep 17 00:00:00 2001 From: Filipe Manana Date: Tue, 1 Jul 2025 15:44:16 +0100 Subject: [PATCH] btrfs: qgroup: fix qgroup create ioctl returning success after quotas disabled When quotas are disabled qgroup ioctls are supposed to return -ENOTCONN, but the qgroup create ioctl stopped doing that when it races with a quota disable operation, returning 0 instead. This change of behaviour happened in commit 6ed05643ddb1 ("btrfs: create qgroup earlier in snapshot creation"). The issue happens as follows: 1) Task A enters btrfs_ioctl_qgroup_create(), qgroups are enabled and so qgroup_enabled() returns true since fs_info->quota_root is not NULL; 2) Task B enters btrfs_ioctl_quota_ctl() -> btrfs_quota_disable() and disables qgroups, so now fs_info->quota_root is NULL; 3) Task A enters btrfs_create_qgroup() and calls btrfs_qgroup_mode(), which returns BTRFS_QGROUP_MODE_DISABLED since quotas are disabled, and then btrfs_create_qgroup() returns 0 to the caller, which makes the ioctl return 0 instead of -ENOTCONN. The check for fs_info->quota_root and returning -ENOTCONN if it's NULL is made only after the call btrfs_qgroup_mode(). Fix this by moving the check for disabled quotas with btrfs_qgroup_mode() into transaction.c:create_pending_snapshot(), so that we don't abort the transaction if btrfs_create_qgroup() returns -ENOTCONN and quotas are disabled. Fixes: 6ed05643ddb1 ("btrfs: create qgroup earlier in snapshot creation") CC: stable@vger.kernel.org # 6.12+ Reviewed-by: Qu Wenruo Signed-off-by: Filipe Manana Reviewed-by: David Sterba Signed-off-by: David Sterba --- fs/btrfs/qgroup.c | 3 --- fs/btrfs/transaction.c | 6 ++++-- 2 files changed, 4 insertions(+), 5 deletions(-) diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c index eb1bb57dee7df..ae9bc7c71a347 100644 --- a/fs/btrfs/qgroup.c +++ b/fs/btrfs/qgroup.c @@ -1662,9 +1662,6 @@ int btrfs_create_qgroup(struct btrfs_trans_handle *trans, u64 qgroupid) struct btrfs_qgroup *prealloc = NULL; int ret = 0; - if (btrfs_qgroup_mode(fs_info) == BTRFS_QGROUP_MODE_DISABLED) - return 0; - mutex_lock(&fs_info->qgroup_ioctl_lock); if (!fs_info->quota_root) { ret = -ENOTCONN; diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c index 2e07c90be5cd1..c5c0d9cf1a808 100644 --- a/fs/btrfs/transaction.c +++ b/fs/btrfs/transaction.c @@ -1735,8 +1735,10 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans, ret = btrfs_create_qgroup(trans, objectid); if (ret && ret != -EEXIST) { - btrfs_abort_transaction(trans, ret); - goto fail; + if (ret != -ENOTCONN || btrfs_qgroup_enabled(fs_info)) { + btrfs_abort_transaction(trans, ret); + goto fail; + } } /* -- 2.47.2