Abstract:
A non-disruptive unassignment of an address from a fabric responsive to a request from a channel adapter. A logout command requests the fabric to unassign an address. The status of the address is thereby changed from active to unassigned and an acknowledgment sent back to the channel adapter.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS  
       [0001]     This application is a divisional application of application Ser. No. 10/043,489 filed Jan. 11, 2002 and assigned to the same assignee as this application. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     The present invention is related to a multipartitioned data processing system and is more particularly related to non-disruptive recovery of a single partition in a multipartitioned data processing system.  
         [0003]     A host Fibre Channel adapter supporting multiple logical partitions (LPARs) often requires multiple Fibre Channel addresses (N_Port IDs). An example of a configuration requiring the adapter to have multiple N_Port IDs is when the adapter is shared by multiple LPARs executing the SCSI/Fibre Channel Protocol (FCP). While methods for obtaining multiple N_Port IDs have recently been developed, there is no existing method by which a specific N_Port ID may be removed. The only way to remove an N_Port ID corresponding to a given LPAR is to remove all N_Port IDs for all LPARs.  
         [0004]     This situation is undesirable because error-recovery actions for errors relating to a given LPAR often require removal and re-initialization of the N_Port ID corresponding to that LPAR. Since the only way to reinitialize the N_Port ID corresponding to the faulted LPAR is to remove all LPAR IDs, then error-recovery actions for a given LPAR disrupt ongoing operations in all other LPARs which are sharing the adapter. A method is needed which can remove the N_Port ID of a given LPAR without affecting ongoing operations in other LPARS.  
         [0005]     Currently, the Logout (LOGO) Extended Link Service (ELS) command is only sent to other (remote) N_Ports; it is not sent to the fabric port (F_Port). This allows a host adapter to log out with a remote N_Port (for situations such as error-recovery), but it does not allow the host adapter to log out with the fabric. In order to log out with the fabric F_Port, link-level primitive sequences are currently required. These primitive sequences not only log out the attached N_Port, but they also reinitialize the synchronization on the link. This may be acceptable for configurations in which the host adapter has only a single N_Port ID, but in cases where the adapter has multiple N_Port IDs, it results in logging out all N_Port IDs for the host adapter.  
         [0006]     Currently, most single host adapters do not have more than one N_Port ID; therefore, there has been no need to remove one N_Port ID without affecting other N_Port IDs assigned to the adapter.  
         [0007]     One alternative to the present invention where a single host adapter does support more than one N_Port ID is to require the adapter to de-register one of its N_Port_IDs from the fabric name-server database. This alternative would require the fabric to provide a name-server which communicates with the fabric F_Port in order to notify the fabric that the N_Port ID had been removed. Requiring the presence of a name server function in the fabric is costly and it requires communication code within the Fibre Channel.  
         [0008]     U.S. Pat. No. 5,276,813 issued Jan. 4, 1994 to Elliott et al. for ACQUIRING ADDRESSES IN AN INPUT/OUTPUT SYSTEM, discloses a computer Input/Output system in which link-level facilities issue an acquire link address frame when initially coming on line. A dynamic switch receiving the frame then assigns a link address to the link-level facility.  
         [0009]     U.S. Pat. No. 5,420,988 issued May 30, 1995 to Elliott for ESTABLISHING LOGICAL PATHS THROUGH A SWITCH BETWEEN CHANNEL AND CONTROL UNITS IN A COMPUTER I/O SYSTEM, discloses a mechanism for assigning multiple logical path identifications with a single physical path.  
         [0010]     U.S. Pat. No. 6,084,859 issued Jul. 4, 2000 to Ratcliff et al. for INTERNET PROTOCOL ASSISTS USING MULTI-PATH CHANNEL PROTOCOL, discloses an apparatus for allowing any initiating host to establish communications with any receiving host in a computing network using a multi-path channel communication protocol.  
       SUMMARY OF THE INVENTION  
       [0011]     In order to remove a single N_Port ID, the usage of the Logout (LOGO) Extended Link Service (ELS) is extended by allowing it to be sent to the fabric at a well-known Fibre Channel address as described below.  
         [0012]     In the following description, an LPAR&#39;s currently-assigned “address” or “N_Port ID” is referred to as the LPAR SID. An LPAR&#39;s permanent name or “N_Port Name,” is referred to here as an LPAR ID.  
         [0013]     The process for removing a single N_Port ID (when multiple N_Port IDs have previously been assigned) is as follows: 
        1. The adapter sends the LOGO ELS to the well-known address for the fabric F_Port (x‘FFFFFE’). The sender&#39;s N_Port ID specified in the LOGO ELS header is one of the currently-assigned LPAR SIDs. The payload of the LOGO ELS also contains an LPAR SID and corresponding N_Port Name (LPAR ID). This is the LPAR SID and LPAR ID to be logged out; there are two variations for the use of this field: 
            (Case a) Require that the LPAR SID and N_Port Name in the LOGO payload be those of the LPAR sending the LOGO ELS. In this case, the LPAR SID specified in the source address of the LOGO ELS header is the same as the LPAR SID specified in the LOGO ELS payload. (In this case, the sending LPAR is logging itself out.)     (Case b) Allow the LPAR SID and N_Port Name in the LOGO ELS payload to be ANY currently-assigned LPAR SID and corresponding LPAR ID. In this case, the LPAR SID specified in the source address of the LOGO ELS header may be different from the LPAR SID specified in the LOGO ELS payload. (In this case, the sending LPAR is logging out another LPAR.)     Case b is desirable if the host adapter had a “base” N_Port ID which controlled all other N_Port IDs. Case a is desirable, otherwise. Case a is also easier for the fabric to implement because the fabric can ignore the N_Port Name field in the LOGO ELS, and can simply log out the N_Port specified by the SID of the LOGO ELS)    
            2. Upon receipt of the LOGO ELS, the fabric removes all resources associated with LPAR SID (and corresponding LPAR ID) being logged out, and sends a link-service accept (LS_ACC) to the adapter. The destination address of the LS_ACC is set to the source address of the LOGO ELS which is the usual procedure.        
 
         [0019]     If the fabric subsequently receives a request from the adapter for a new SID after it has been removed, the fabric may reassign any unused LPAR SID to the adapter, or it may reassign the same (if currently not assigned elsewhere) SID previously removed by the LOGO ELS. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]     These and other objects will be apparent to one skilled in the art from the following detailed description of the invention taken in conjunction with the accompanying drawings in which:  
         [0021]      FIG. 1  is a schematic diagram of a data processing network having a server having multiple LPARs, each with an LPAR ID and at least one N_Port, the network having a network fabric;  
         [0022]      FIG. 2  is a flowchart of the procedure followed by the N_Port of the system of  FIG. 1  for requesting an N_Port address (SID) from the fabric on behalf of an LPAR ID;  
         [0023]      FIG. 3  is a flowchart of the procedure followed by the fabric of  FIG. 1  for providing addresses (SIDs) to the N_Port;  
         [0024]      FIG. 4  is an illustration of portions of a LOGO ELS command for removing a SID, the LOGO ELS command including a header portion and a payload or data portion;  
         [0025]      FIG. 5  is a flowchart of the procedure followed by the channel for the case in which the LOGO ELS command is on behalf of the LPAR ID and SID to be removed (Case a);  
         [0026]      FIG. 6  is a flowchart of the procedure followed by the fabric for Case a;  
         [0027]      FIG. 7  is a flowchart of the procedure followed by the channel for the case in which the LPAR ID and SID to be removed is not the same as the LPAR ID and SID sending the LOGO ELS command (Case b); and  
         [0028]      FIG. 8  is a flowchart of the procedure followed by the fabric for Case b. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0029]      FIG. 1  is a schematic diagram of a data processing network usable with the present invention. The data processing network includes a server or host  100  which may be, for instance, an IBM zSeries 900 server. The server  100  includes an operating system which provides for supporting multiple logical partitions (LPARs)  102   a - 102   n . Each LPAR  102  communicates with I/O devices through channel adapters, as is well known. The server  100  is connected to a fabric  110  by a channel adapter  104 , with the fabric  110  being connected to one or more controllers  120   a - 120   m  controlling I/O devices (not shown) as is well known. The connection and sending of data between the server  100 , the fabric  110 , and the controllers  120  may, for instance, be as described in proposed standard Fibre Channel Framing and Signaling (FC-FS Rev. 1.40) NCITS Project 1331-D, Oct. 15, 2001.  
         [0030]     The adapter  104  is, in the exemplary embodiment, hardware having a software interface for communicating with the LPARS  102 , and includes an N_Port  106  for connecting to an F_Port  112  of the fabric  110 . Although a single port, the N_Port  106  recognizes multiple addresses, one address for each of the partitions  1 - n  (LPARs  102   a - 102   n ). Once the address for partition  102  is established, communication by, for instance, a controller to that particular partition  102  may be effected by communicating with the partition&#39;s assigned address. A name server  114  is provided in the fabric  110  which includes an address table  116 . This address table includes, among other things, an identification of each partition  102  (LPAR ID), and its corresponding N_Port address (SID). Thus, in order to communicate with a partition, the name server  114  may be accessed to determine the N_Port address (SID) corresponding to that partition  102  (LPAR ID), and data is then sent to that N_Port address (SID). It will be understood that each F_Port  112  in the fabric  110  acts to receive and transmit data and commands between the fabric  110  and the channel adapter  104  or the controllers  120   a - 120   m , as is well known.  
         [0031]      FIG. 2  is a flow diagram of the procedure followed by the N_Port  106  of a fibre channel to obtain an N_Port address SID) from the fabric  110 . The procedure starts at  200 . If at  201 , this is the first address for the N_Port  106 , a Fabric Login extended link service (FLOGI ELS) command is issued to the fabric  110 . The FLOGI ELS command includes an identification for the partition  102  requesting the address, and has a source address of all zeros to indicate to the fabric  110  that an N_Port address identifier is being requested. At  203 , the address assigned by the Fabric  110  is received. The FLOGI command is sent in this embodiment on behalf of the first partition  102  requesting an address. This first request may always be assigned by a selected one of the partitions, or may be the first partition needing an address, or may be selected by, for instance, a round robin scheme, as may be desired.  
         [0032]     This is not the first address being selected for a partition  102 , at  204 , a Fabric Discovery Extended Link Service (FDISC ELS) command is issued using either the source address identifier of zero, or, if known, the new source address identifier using identical service parameters as provided in the original FLOGI command. At  205 , the N_Port  106  receives the address assigned or confirmed by the fabric  110  for use with the requesting partition  102 .  
         [0033]      FIG. 3  is a flow diagram of the procedure followed by the fabric  110  in assigning the address identifications requested in the flowchart of  FIG. 2 , and starts at  200 . At  301 , the fabric  110  receives the ELS command with a partition ID. The partition ID (LPAR ID) may be the worldwide partition number, or any other identification scheme to identify the partition to be associated with the N_Port address identification. At  302 , it is determined if the command is a FLOGI command. If yes, at  303  an address table  116  is established in the name server  114  for the N_Port  106 . At  304 , the first address identification (SID) is assigned for this N_Port  106 . At  305 , the address identification (SID) is recorded in the table  116 , along with the partition identification (LPAR ID), and other parameters needed for the communications protocol to be used to transfer commands and data between the N_Port  106  and the controllers  120   a - m . At  306 , the address (SID) is returned to the N_Port  106 .  
         [0034]     If the ELS is an FDISC command at  307 , the next address (SID) is assigned or confirmed at  308 . If a new source address identification is supplied by the FDISC ELS command, that address identification, if acceptable, is used. If an address is not supplied, the next available address is assigned by  110  in accordance with a desired scheme which insures that duplicate numbers are not assigned. In addition at  308 , if the partition ID already has an address identification in the table  116 , the address identification is updated by the identification in the FDISC ELS command. Thus, the FDISC ELS command may be used to request an address be assigned, may have a proposed address identification confirmed, or may update an old address identification with a new address identification. Then at  305 , the partition identification, address identification, and other parameters are recorded in the address table  116 , and at  306 , the assigned, confirmed, or updated address identification is returned to the N_Port  106 . It will now be understood that normal frame reception and transmission can begin. The controllers will see “n” different adapters, one adapter for each partition, but there will be only one channel adapter N_Port  106  with “n” different addresses.  
         [0035]     Returning to  FIG. 1 , if a SID is to be removed, a LOGO command  125  is sent from the channel adapter  104  to the fabric F_Port  112  with an identification of the SID to be removed. An link-service accept (LS_ACC)  126  is sent from the fabric F_Port  112  to the adapter  104  after the designated SID has been non-disruptively removed. A SID for the removed LPAR ID can be reacquired with an FDISC, as previously described.  
         [0036]      FIG. 4  is an illustration of portions of a LOGO ELS command  401  for removing a SID. The LOGO ELS command includes a header portion  402  and a payload or data portion  403 . The header portion  402  includes a source ID  405  of the LOGO ELS command  401 , and a destination ID of x‘FFFFFE’  406 , which is the address for the fabric F_Port  112 . The Source ID may be the LPAR SID of the LPAR ID sending the LOGO ELS command. The payload portion of the LOGO ELS command includes the LPAR ID  408  to be logged, and the LPAR SID  410  to be logged out. It will be understood that  FIG. 4  only illustrates the relevant portions of the LOGO ELS command, and that both the header  402  and payload  403  of the command  401  may include other data fields and data, as well understood in the art.  
         [0037]     The process for removing a single SID (when multiple SIDs have previously been assigned) is as follows: 
        1. The adapter sends the LOGO ELS  401  to the well-known address for the fabric F_Port (x‘FFFFFE’)  406 . The sender&#39;s N_Port ID  405  specified in the LOGO ELS header  402  is one of the currently-assigned LPAR SIDs. The payload  403  of the LOGO ELS  401  also contains an LPAR SID  410  and corresponding LPAR ID  408 . This is the LPAR SID and LPAR ID to be logged out. There are two variations or cases for the use of this field: 
            (Case a) Require that the LPAR SID  410  and LPAR ID  408  in the LOGO payload  403  be those of the LPAR sending the LOGO ELS  401 . In this case, the LPAR SID specified in the source address  405  of the LOGO ELS header  402  is the same as the LPAR SID  410  specified in the LOGO ELS payload  403 . (In this case, the sending LPAR is logging itself out.)     (Case b) Allow the LPAR SID  410  and LPAR ID  408  in the LOGO ELS payload  403  to be ANY currently-assigned LPAR SID and corresponding LPAR ID. In this case, the LPAR SID specified in the source address  405  of the LOGO ELS header  402  may be different from the LPAR SID  410  specified in the LOGO ELS payload  403 . (In this case, the sending LPAR is logging out another LPAR.)     Case b is desirable if the host adapter  104  had a “base” N_Port ID which controlled all other N_Port IDs. Case a is desirable, otherwise. Case a is also easier for the fabric  110  to implement because the fabric  110  can ignore the N_Port Name field  408  in the LOGO ELS  401 , and can simply log out the N_Port specified by the SID  410  of the LOGO ELS  401 )    
            2. Upon receipt of the LOGO ELS  401 , the fabric removes all resources associated with LPAR SID  410  (and corresponding LPAR ID  408 ) being logged out, and sends a link-service accept  126  (LS_ACC) to the adapter  104 . The destination address of the LS_ACC  126  is set to the source address  401  of the LOGO ELS which is the usual procedure.        
 
         [0043]     If the fabric subsequently receives a request from the adapter  104  for a new SID after it has been removed, the fabric may reassign any unused LPAR SID to the adapter  104 , or it may reassign the same (if currently not assigned elsewhere) SID previously removed by the LOGO ELS.  
         [0044]      FIG. 5  is a flowchart of the procedure followed by the channel in Case a, starting at  501 . At  502 , the LPAR to be logged out sends a LOGO containing its own LPAR SID and its own LPAR ID in the LOGO ELS command  125  (shown at  401  of  FIG. 4 ). A check is made at  503  to determine if an LS_ACC  126  is received at the channel adapter  104 . If yes, at  505  LPAR is reinitialized. If desired, a SID may be re-acquired with an FDISC, as previously explained. The procedure ends at  506 . If an LS_ACC is not received at  503 , an error is detected at  508 , and a low-level recovery is performed.  
         [0045]      FIG. 6  is a flowchart of the procedure followed at the fabric side for Case a and starts at  601 . At  602 , a LOGO is received containing the senders SID and LPAR ID. A check at  603  checks the address table  116  to see if the LPAR ID and SID are active. If yes, at  605  the senders LPAR ID is logged out and the sender&#39;s SID is made available for reuse. At  606 , an LS_ACC accept is sent back to the channel adapter  104 . If the check at  603  is no, at  610  a Link Service Reject (LS_RJT) is returned to the channel adapter  104 .  
         [0046]      FIG. 7  is a flowchart of the procedure followed by the channel in Case b, starting at  701 . At  702 , an LPAR wanting to log out another SID and LPAR ID sends a LOGO containing the LPAR ID and SID to be logged out (shown at  408  and  410  of  FIG. 4 ). A check is made at  703  to determine if an LS_ACC  126  is received at the channel adapter  104 . If yes, at  705  LPAR to be logged out is reinitialized. If desired, a SID may be re-acquired with an FDISC, as previously explained. The procedure ends at  706 . If an LS_ACC is not received at  703 , an error is detected at  708 , and a low-level recovery is performed.  
         [0047]      FIG. 8  is a flowchart of the procedure followed at the fabric side for Case b and starts at  801 . At  802 , a LOGO is received containing any SID and LPAR ID to be logged out. A check at  803  checks the address table  116  to see if the LPAR ID and SID are active. If yes, at  805  the LPAR ID  408  specified in the payload  403  of the LOGO ESC is logged out and the SID specified in  410  is made available for reuse. At  806 , an LS_ACC accept is sent back to the channel adapter  104 . If the check at  803  is no, at  810  a Link Service Reject (LS_RJT) is returned to the channel adapter  104 .  
         [0048]     While the preferred embodiment of the invention has been illustrated and described herein, it is to be understood that the invention is not limited to the precise construction herein disclosed, and the right is reserved to all changes and modifications coming within the scope of the invention as defined in the appended claims.