Method and arrangement for communicating with SCSI devices

• US 6,934,711 B2
• Filed: 10/01/2002
• Issued: 08/23/2005
• Est. Priority Date: 10/01/2002
• Status: Active Grant

• Current Assignee: Valtrus Innovations Limited (f/k/a Dolya Holdco 9 Limited) (Key Patent Innovations Limited)
• Original Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Inventors: Krishnamurthy, Vikram, Pooni, Subramaniyam, Mangalore, Rajkumar, Srinath, Vijay
• Primary Examiner(s): Kindred, Alford W.
• Application Number:
  US10/260,412
• Publication Number:
  US 20040064460A1
• Time in Patent Office: 1,057 Days
• Field of Search: 707 1- 3, 707/100, 707/200, 710 9- 10, 710/56, 710/62, 710/72
• US Class Current: 1/1
• CPC Class Codes: G06F 3/0607 by facilitating the process of upgrading existing storage systems, e.g. for improving compatibility between host and storage device
• CPC Class Codes: G06F 3/0635 by changing the path, e.g. traffic rerouting, path reconfiguration
• CPC Class Codes: G06F 3/0661 Format or protocol conversion arrangements
• CPC Class Codes: G06F 3/067 Distributed or networked storage systems, e.g. storage area networks [SAN], network attached storage [NAS]
• CPC Class Codes: Y10S 707/99931 Database or file accessing

Abstract

A method and arrangement, for use in a system having a host and one or more small computer system interface (SCSI) devices, are described for enabling a user application accessing the system to communicate with one or more of the SCSI devices. The method and arrangement serve to overcome a device node limitation observed in standard Linux, which limits the number of devices a user application may communicate with to 128 SCSI disk (sd) devices or 256 SCSI generic (sg) devices. The method and arrangement provide a pass through capability by allowing the user application to directly talk to any SCSI device by using virtual handles, thereby overcoming the device node limitation observed in standard Linux.

Claims

1. A method, for use in a system having a host and one or more small computer system interface (SCSI) devices, the method enabling a user application accessing the system to communicate with one or more of the SCSI devices, comprising the steps of:

querying a kernel component in the system for all SCSI devices in the system that are known to the kernel component;

preparing a buffer of virtual handles at the kernel component in response to the querying step, each virtual handle representing a known SCSI device;

forwarding the buffer to the user application;

issuing a command data structure to the kernel component, the command data structure containing the virtual handles and command information;

comparing, at the kernel component, each virtual handle to a list of SCSI device data structures of said SCSI devices known to the kernel component, and

transporting the command data structure to SCSI devices, when there is a match between a virtual handle and a corresponding device data structure of a SCSI device.

2. The method of claim 1, wherein said transporting step establishes a communication path between the user application and the SCSI devices.

3. The method of claim 1, wherein the preparing step further comprises

parsing a list of known SCSI device pointers (SDP), each SDP pointing to a one of said known SCSI devices;

extracting SCSI address information to the SCSI device from each of the known SDPs; and

converting each extracted SCSI address information into a virtual handle; and

building said buffer with said virtual handles.

4. The method of claim 3, wherein said extracting step includes extracting host, bus, target and logical unit number (lun) information, (h, b, t, l) from each known SDP, each (h, b, t, l) address indicating a path from the host to a SCSI device in the system.

5. The method of claim 4, wherein said converting step includes adding an identifier to each (h, b, t, l) to create a virtual handle in a form cXbYtZlN,

where c represents an identifier indicating host information with X being a host number (h) in the (h, b, t, l) address, b representing an identifier indicating bus information with Y being a bus number (b) in the (h, b, t, l) address, t representing an identifier indicating target information with Z being a target number (t) in the (h, b, t, l) address, and l representing an identifier indicating lun information with N being the (lun) in the (h, b, t, l) address.

6. The method of claim 1, wherein the comparing step further comprises,

parsing a list of known SCSI device pointers (SDP) at the kernel component, each SDP being a device data structure that points to one of said known SCSI devices and including SCSI address information which indicates a path said one known SCSI device;

and

matching the virtual handle to SCSI address information in at least one SDPs.

7. The method of claim 6, wherein said transporting step includes

using SDPs resulting from said matching step in order to transport a command data structure to one or more SCSI devices, wherein the command data structure contains a SCSI command requesting data from a SCSI device.

8. The method of claim 1, wherein the command data structure contains a SCSI command requesting data from a SCSI device, and wherein the virtual handle is useable to transport the SCSI command to a SCSI device that has an associated device file name.

9. The method of claim 1, wherein the command data structure contains a SCSI command requesting data from a SCSI device, and wherein the virtual handle is useable to transport the SCSI command to a SCSI device that does not have an associated device file name.

10. The method of claim 1, wherein said SCSI devices include at least one or more of SCSI disk (sd) devices and SCSI generic (sg) devices, and wherein the user application communicates with a number of SCSI devices in excess of a Linux limitation of 128 sd devices or 256 sg devices.

11. An arrangement in a system having a host and one or more small computer system interface (SCSI) devices, the arrangement enabling a user application accessing the system to communicate with one or more of the SCSI devices, comprising:

means for querying a kernel component in the system for all SCSI devices in the system that are known to the kernel component;

means for preparing a buffer of virtual handles at the kernel component in response to the querying step, each virtual handle representing a known SCSI device;

means for forwarding the buffer to the user application;

means for issuing a command data structure to the kernel component, the command data structure containing the virtual handles and command information;

means for comparing, at the kernel component, each virtual handle to a list of SCSI device data structures of said SCSI devices known to the kernel component, and

means for transporting the command data structure to SCSI devices, when there is a match between a virtual handle and a corresponding device data structure of a SCSI device.

12. The arrangement of claim 11, wherein a communication path is established between the user application and the SCSI devices when the command data structure is received by the SCSI devices.

13. The arrangement of claim 11,

wherein the means for querying further includes a user interface for issuing an input/output control call (IOCTL) to the filter component to return identifier information for all devices known to the kernel component, and

wherein the kernel component is a filter driver adapted to be inserted into the system to intercept commands, via the interface, from the user application in order to facilitate communication between the user application and SCSI devices in the system.

14. The arrangement of claim 11,

wherein the means for preparing further includes the kernel component searching a database containing a list of known SCSI device pointers (SDP), each SDP pointing to a one of said known SCSI devices;

extracting SCSI address information to the SCSI device from each of the known SDPs in the database, and converting each extracted SCSI address information into a virtual handle that it inserts in the buffer.

15. The arrangement of claim 14, wherein the SCSI address information is host, bus, target and logical unit number (lun) information, (h, b, t, l) of each known SDP, each (h, b, t, l) address indicating a path from the host to a SCSI device in the system.

16. The arrangement of claim 14, wherein the kernel component adds an identifier to each (h, b, t, l) to create a virtual handle in a form cXbYtZlN,

where c represents an identifier indicating host information with X being a host number (h) in the (h, b, t, l) address, b representing an identifier indicating bus information with Y being a bus number (b) in the (h, b, t, l) address, t representing an identifier indicating target information with Z being a target number (t) in the (h, b, t, l) address, and l representing an identifier indicating lun information with N being the (lun) in the (h, b, t, l) address.

17. The arrangement of claim 11, wherein the means for comparing further includes the kernel component searching a database of known SCSI device pointers (SDP), each SDP being a device data structure that points to one of said known SCSI devices and including SCSI address information which indicates a path said one known SCSI device, and the kernel component matching the virtual handle to SCSI address information in at least one SDP.

18. The arrangement of claim 11, wherein the command data structure contains a SCSI command requesting data from a SCSI device, and wherein the virtual handle is useable to transport the SCSI command to a SCSI device that has an associated device file name.

19. The arrangement of claim 11, wherein the command data structure contains a SCSI command requesting data from a SCSI device, and wherein the virtual handle is useable to transport the SCSI command to a SCSI device that does not have an associated device file name.

20. The arrangement of claim 11, wherein said SCSI devices include at least one or more of SCSI disk (sd) devices and SCSI generic (sg) devices, and wherein the user application communicates with a number of SCSI devices in excess of a Linux limitation of 128 sd devices or 256 sg devices.

21. A computer program product, for use in a system having a bus, a host connected to the bus, and one or more small computer system interface (SCSI) devices connected to the bus, the computer program product comprising a computer-readable medium having computer program logic stored thereon for enabling a processor of the product to allow a user application accessing the system to communicate with one or more of the SCSI devices, the computer program logic causing the processor to perform the steps of:

querying a kernel component in the system for all SCSI devices in the system that are known to the kernel component;

preparing a buffer of virtual handles at the kernel component in response to the querying step, each virtual handle representing a known SCSI device;

forwarding the buffer to the user application;

issuing a command data structure to the kernel component, the command data structure containing the virtual handles and command information;

comparing, at the kernel component, each virtual handle to a list of SCSI device data structures of said SCSI devices known to the kernel component, and

transporting the command data structure SCSI devices, where there is a match between a virtual handle and a corresponding device data structure of a SCSI device, so as to establish a communication path between the user application and the SCSI devices.