6.16-stable review patch. If anyone has any objections, please let me know.
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From: Filipe Manana fdmanana@suse.com
commit 08530d6e638427e7e1344bd67bacc03882ba95b9 upstream.
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 wqu@suse.com Signed-off-by: Filipe Manana fdmanana@suse.com Reviewed-by: David Sterba dsterba@suse.com Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/btrfs/qgroup.c | 3 --- fs/btrfs/transaction.c | 6 ++++-- 2 files changed, 4 insertions(+), 5 deletions(-)
--- a/fs/btrfs/qgroup.c +++ b/fs/btrfs/qgroup.c @@ -1690,9 +1690,6 @@ int btrfs_create_qgroup(struct btrfs_tra 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; --- a/fs/btrfs/transaction.c +++ b/fs/btrfs/transaction.c @@ -1735,8 +1735,10 @@ static noinline int create_pending_snaps
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; + } }
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