Method and system for hybrid direct input/output (I/O) with a storage device
A method including intercepting a OFR for a file issued by an application to a FS, forwarding the OFR to the FS, receiving from the FS a FD for the file, issuing a SR for the file to the FS. The further method includes receiving from the FS status information for a target device on which the file is located, where the status information includes an OID for the file, storing a mapping of FD to the OID, intercepting a first FOR for the file, making a determination the that the first FOR is one of a read request and a write request, based on the determination, making another determination that the target device supports the direct I/O protocol, and issuing a DI request to the target device using the OID for the file, where the DI request is not processed by the FS.
1. A non-transitory computer readable medium comprising instructions, which when executed by a processor perform a method, the method comprising:
intercepting, by a direct IO library, a first file operation request (FOR) for a file, wherein the first FOR comprises a file descriptor (FD) for the file;
making, using the first FOR, a first determination that the first FOR is one selected from a group consisting of a read request and a write request;
based on the first determination, making a second determination that a target device on which the file is located supports a direct I/O protocol; and
based on the second determination, issuing a direct I/O request to the target device using an OID for the file, wherein the direct I/O request is not processed by a file system (FS).
2. The non-transitory computer readable medium of claim 1 , the method further comprising:
receiving a notification, in response to the direct I/O request, that the direct I/O request is completed, wherein the notification is sent directly from the target device to the host and wherein the FS does not receive the notification.
3. The non-transitory computer readable medium of claim 1 , the method further comprising:
after issuing the direct I/O request to the target device for the file:
receiving a second FOR for the file, wherein the second FOR comprises the FD;
making a third determination the that the second FOR is not one selected from a group consisting of the read request and the write request; and
based on the third determination, forwarding the second FOR to the FS via the kernel module in the kernel-level of the host.
4. The non-transitory computer readable medium of claim 1 , the method further comprising:
creating a unified address space comprising a memory location on the target device prior to the issuance of the direct I/O request,
wherein issuing the direct I/O request comprises storing the direct I/O request directly in the memory location on the target device.
5. The non-transitory computer readable medium of claim 1 , wherein issuing the direct I/O request to the target device comprises storing the direct I/O request in a memory location on the target storage device, wherein the memory location is part of a unified address space that is directly accessible by the host.
6. The non-transitory computer readable medium of claim 5 , wherein the memory location is associated with a submission queue.
7. The non-transitory computer readable medium of claim 1 , the method further comprising:
prior to intercepting the first FOR:
intercepting, in a user-level of a host, an open file request (OFR) for the file issued by an application to the FS;
forwarding the OFR to the FS, wherein the FS is located in the user-level and the OFR is forwarded to the FS via a kernel module in a kernel-level of the host;
receiving from the FS, in response to the OFR, information that is used to generate the FD for the file.
8. The non-transitory computer readable medium of claim 1 , wherein making the second determination comprises using status information for the target device.
9. The non-transitory computer readable medium of claim 8 , the method further comprising:
issuing, to the FS, a status request (SR);
receiving from the FS, in response to the SR, the status information for the target device, wherein the status information specifies that the target device supports the direct I/O protocol.
10. The non-transitory computer readable medium of claim 1 , the method further comprising:
obtaining an OID for the file prior to issuing the direct I/O request to the target device.
11. The non-transitory computer readable medium of claim 10 , wherein the direct I/O request comprises the OID.
12. The non-transitory computer readable medium of claim 10 , wherein obtaining the OID comprises using a mapping of the FD to the OID.
13. The non-transitory computer readable medium of claim 10 , wherein the OID is obtained in response to a status request issued to the target device.
14. A system, comprising:
a processor;
a user-level comprising an application, a direct I/O library, and a file system (FS); and
a kernel-level, executing on the processor, comprising a kernel module;
wherein the direct I/O library is configured to:
intercept a first file operation request (FOR) for the file, wherein the first FOR comprises a file descriptor (FD) for the file,
make, using the first FOR, a first determination that the first FOR is one selected from a group consisting of a read request and a write request,
based on the first determination, make a second determination that a target device on which the file is located supports the direct I/O protocol, and
based on the second determination, issue a direct I/O request to the target device using an OID for the file, wherein the direct I/O request is not processed by the FS;
wherein the target device is operatively connected to the system.
15. The system of claim 14 , further comprising:
a kernel-level direct I/O library configured to create a unified address space comprising a memory location on the target device prior to the issuance of the direct I/O request, wherein issuing the direct I/O request comprises storing the direct I/O request directly in the memory location on the target device.
16. The system of claim 14 , wherein the unified address is implemented using PCIe and a non-transparent bridge interposed between the system and the target device.
17. The system of claim 14 , wherein the direct I/O library is further configured to:
after issuing the direct I/O request to the target device for the file:
receive a second FOR for the file, wherein the second FOR comprises the FD;
make a third determination that the second FOR is not one selected from a group consisting of the read request and the write request;
based on the third determination, forward the second FOR to the FS via the kernel module.
18. The system of claim 17 , wherein the second FOR is one selected from a group consisting of a modify operation and a delete operation.
19. The system of claim 17 , wherein the FS is further configured to:
receive the second FOR;
service the second FOR using the direct I/O library to generate a response;
sending the response to the application via the kernel module and the direct I/O library.
20. The system of claim 14 , wherein the kernel module is a File system in USEr space (FUSE) module.
21. The system of claim 14 , wherein the target device comprises persistent storage.
22. The system of claim 21 , wherein the persistent storage comprises a solid state memory device.