JPH02263262A - Access control system for shared file - Google Patents

Abstract

PURPOSE:To omit the use of the special hardware and to prevent the deterioration of throughput of a file access owing to the transfer of data carried out via another bus between hosts by adding a shared file to which the accesses are possible from both hosts onto an SCSI bus and attaining the access control. CONSTITUTION:It is checked whether a file control table had a change or not every time both hosts 12a and 12b carry out the processes in accordance with the request contents received from a user application. If the file control table had a change, this table is written into another file control table stored in a shared file storing device 15. then the change of the control table is given to another host by means of a command of a small computer system interface. Receiving this information, the host reads a file control table out of the device 15 and updates its own file control table. As a result, the file access control is attained between the hosts without using any special hardware.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a method for controlling file access when sharing files among multiple hosts.

(Prior Art) Two typical methods for commonly accessing files among multiple hosts are shown in FIGS. 5 and 6.

Generally, when a shared file is accessed from two different hosts, if both hosts maintain their own file management information in their own memory, the file management information will change as the file is updated. In this case, unless the file management information held by the other host is similarly rewritten, the integrity of the files between the two hosts will be lost.

The method shown in Figure 5 solves this problem by
The file management information 4 is centrally managed by one of the hosts 1 (this host is called a mask), and the other host (called a slave) is managed by a LAN (Local Area Network) etc. connected between both hosts. The access request is transmitted to the master 1 side via the common bus 3, and the master 1
The side is configured to return the result of accessing the common file 5 to the slave 2 side via the common bus 3.

The system shown in FIG. 6 is one in which a dedicated signal line 10 is provided for controlling access between both hosts.

In this method, both hosts 6 and 7 hold file management information 8 and 9, respectively, and if any changes are made to the file management information, this is communicated to the other host via a dedicated signal line 10. It will be done.

When the other host receives the signal, it can maintain the integrity of the file management information between the two hosts 6 and 7 by updating the management information in its own memory from the shared file (disk) 11. It becomes.

(Problem to be Solved by the Invention) However, in the case of the system shown in FIG. Both software 1 and 2 require special software to process this.

Furthermore, since file access on the slave side is performed via the bus 3, there are drawbacks such as throughput being relatively slow depending on the transfer speed of the bus.

Further, in the case of the method shown in FIG. 6, unlike the case described above, it is possible to reduce the drop in throughput, but a special signal line 10 is required to connect both hosts.

This invention was made in view of the above problems,
The purpose of this is to enable file access between hosts without the need for special hardware when a shared file is set up on the 5C8I (Small Computer System Interface) that can be accessed by multiple hosts. The objective is to provide a control method that

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention provides a control method for accessing a shared file from a plurality of hosts. Every time a process corresponding to the request is executed, it is checked whether a change has occurred in the file management table, and if a change has occurred, the changed file management table is transferred to the file management table in the shared file storage device. In addition to notifying other hosts of a change in the file management table using the 5CSI bus interface command, the host also received a notification that a change had occurred in the file management table. The host reads the file management table from the shared file storage device and updates its own file management table.

(Function) According to this configuration, since change notifications are sent to the file management table using commands of the 5C3I bus interface, file access control between hosts is possible without the need for special hardware. can be done.

(Embodiment) FIG. 1 is a block diagram schematically showing a hardware configuration that is a premise of a shared file access control method according to the present invention.

In the figure, 12a is one host (a),
12b is the other host (b).

Host a and host b are connected via a 5C8I (small computer system interface) bus 13 and have inshake/target functions on the 5csr bus interface.

On the 5C8I bus 13, there is a device 15 (-a hard disk for boat fishing) that stores shared files that can be accessed by both hosts 12a and 12b.

14 is a software module of a bus driver portion for controlling the 5csr bus controller within the host 12a.

16 is target device driver software for controlling the device (target) 15 in which the shared file is stored, and 17 is a virtual device driver for performing a data communication function between hosts.

Reference numeral 18 denotes a file system for processing input/output requests for various shared files from the application program 19. This file system 18 accepts input/output requests for various shared files from user applications, and processes each of them. It functions to manage file management information regarding shared files, issue actual input/output requests to each device driver, and return the obtained results to the user application 19.

The file management information managed by the file system 18 includes file name, file size, relative block number 2 creation/update date and time, free block information, and the like.

Next, FIG. 2 shows an example of the command format of the 5ICS bus interface used in this embodiment.

Next, on the premise of the above hardware configuration, the processing of the file system 1B necessary for realizing the method of the present invention will be described.

FIG. 3 is a flowchart showing the processing flow of the file system 18 when the user application program 19 issues an input/output request for a shared file to the file system 18.

The file system 18 is the user application 19
When called by issuing an input/output request from , first, a device reservation process is performed for the device (target) 15 in which a file is stored (step 301).

Device reservation processing is performed by the target device driver 16.
RESERV of the 5C8I bus interface via
This is accomplished by sending the E command (command code 16th) to the target.

When the target device 15 receives this command, it is reserved for use by the host (initiator) that issued the command, and from then on until the RELEASE command (command code 1°7H) is sent by the initiator. Access from other hosts is prohibited, allowing exclusive control of the device.

When the file system 18 successfully reserves the device, it next checks a modify flag indicating whether the file management information has been updated from another host (step 302).

If the modify flag is set (step 302 YES), the file management information is read from the device where the file is actually stored (step 303), and the values in memory are updated to the latest state. <Step 304) At this point, the modify flag is cleared.

If the modify flag is not set (step 302 NO>), the management information on the memory is used as is without being read from the device 15.

Thereafter, the file system 18 executes processing in response to various input/output requests from the user application 19 (step 305).

If the file management information is changed due to the processing of the input/output request (step 306 YES), the file management information is written back to the device 15 (step 306).
07) A message indicating that the file management information has been modified is sent to the other host via the lower layer device driver of the processor management communication. (Step 308).

At this time, the message transmission to the other host is 5csi.
This is done using the bus interface WRITE command (command code 0AH).

When the message notification is completed, the file system issues a RELEASE command (command code 1) of the SCSI bus interface via the target device driver 16.
7H), the device 15 is released (step 309).

By performing this series of procedures for shared files from the user application 19, files can be integrated between both hosts.

Next, a process when the file system 18 receives a notification of data indicating that file management information has been modified from a partner host will be described.

FIG. 4 is a flowchart showing the flow of data reception processing of the file system 18.

The data reception processing routine of the file system 18 from the partner host is activated when the file system is initialized, and is always in a state where data is input via the interprocessor communication driver.

In this case, the host functions as a target and receives the SCSI bus interface WRITE command (command code 0AI-) from the other host (initiator).
1), the data following the command is fetched (step 401).

When the interprocessor communication driver 17 finishes taking in the data, it returns control to the data reception processing routine placed in the input section of the file system.

When control is returned, the data reception processing routine checks the contents of the received data, and if the message is from the other host indicating modification of file management information, it sets the modify flag in the memory. (step 404). In the case of other messages (step 402 NO>), the process corresponding to each message is executed (step 403).
.

When the processing of each message is completed, the data reception processing routine again waits for the next data to be input.

[Effects of the Invention] As is clear from the above explanation, according to the method of the present invention, a shared file that can be accessed from two hosts on the 5C8I path can be easily realized, and the method for controlling access can be easily realized. Since no special bird air is required and all data and control are executed via the 5C8I bus, it is possible to prevent a drop in file access throughput due to data transfer via another bus between potos.

[Brief explanation of drawings]

Figure 1 is a block diagram schematically showing the hardware configuration that is the premise of the method of the present invention, and Figure 2 is a block diagram of the S
Figure 3 is a flowchart showing the file system processing flow when a shared file input/output request is issued from a user application program to the file system. Figure 4 is a diagram showing the command format of the CSI bus interface. FIG. 5 is a flowchart showing the flow of data reception processing of the file system. FIG. 6 is a block diagram schematically showing two typical methods for commonly accessing files among multiple hosts. 12a, 12b---R strike 13...5csr bus 14...5csr bus driver 15...shared file storage device 16...target device driver 17...interprocessor communication driver 18...file system

Claims (1)

[Claims] (1) In a control method in which shared files are accessed from multiple hosts, each host checks whether any changes have occurred in the file management table each time it executes processing corresponding to the request from the user application. If a change occurs, the changed file management table is written to the file management table in the shared file storage device, and then SCSI notifies other hosts that the file management table has changed. While this is done using bus interface commands, other hosts that receive notification that a change has occurred in the file management table read the file management table from the shared file storage device and update their own file management table. A shared file access control method characterized by: