[LU-5453] mdt_attr_set() uses EX lock for slave 0, PW for master and other slaves

• Type: Bug
• Resolution: Fixed
• Priority: Minor
• Fix Version/s: Lustre 2.7.0
• Affects Version/s: Lustre 2.7.0
• Labels: dne2 mdt
• Severity: 3
• Assignee: John Hammond
• Reporter: John Hammond

Description

In the striped directory case of mdt_attr_set() we use a EX lock on slave 0 while we use a PW lock on the master inode and the other slaves:

mdt_attr_set()
	__u64 lockpart = MDS_INODELOCK_UPDATE;

	if (ma->ma_attr.la_valid & (LA_MODE|LA_UID|LA_GID))
		lockpart |= MDS_INODELOCK_LOOKUP | MDS_INODELOCK_PERM;

        lh = &info->mti_lh[MDT_LH_PARENT];
	mdt_lock_reg_init(lh, LCK_PW);

        rc = mdt_object_lock(info, mo, lh, lockpart, MDT_LOCAL_LOCK);
        if (rc != 0)
        	RETURN(rc);

        s0_lh = &info->mti_lh[MDT_LH_LOCAL];
        mdt_lock_reg_init(s0_lh, LCK_EX);
        rc = mdt_lock_slaves(info, mo, LCK_PW, lockpart, s0_lh, &s0_obj, einfo);
        if (rc != 0)
        	GOTO(out_unlock, rc);

Because the locking order is master, slave0, then other slaves this seems prone to causing deadlocks.