btrfs: qgroup: fix sleep from invalid context bug in btrfs_qgroup_inherit()

In the Linux kernel, the following vulnerability has been resolved:

btrfs: qgroup: fix sleep from invalid context bug in btrfs_qgroup_inherit()

Syzkaller reported BUG as follows:

BUG: sleeping function called from invalid context at

include/linux/sched/mm.h:274

Call Trace:

<TASK>

dump_stack_lvl+0xcd/0x134

__might_resched.cold+0x222/0x26b

kmem_cache_alloc+0x2e7/0x3c0

update_qgroup_limit_item+0xe1/0x390

btrfs_qgroup_inherit+0x147b/0x1ee0

create_subvol+0x4eb/0x1710

btrfs_mksubvol+0xfe5/0x13f0

__btrfs_ioctl_snap_create+0x2b0/0x430

btrfs_ioctl_snap_create_v2+0x25a/0x520

btrfs_ioctl+0x2a1c/0x5ce0

__x64_sys_ioctl+0x193/0x200

do_syscall_64+0x35/0x80

Fix this by calling qgroup_dirty() on @dstqgroup, and update limit item in

btrfs_run_qgroups() later outside of the spinlock context.