Performing disk reads from within a kernel module

Question

Hi,
i want to perform direct io reads from a specific disk from within a kernel module. i tried to perform a physio call, but although the function returns 0 (success) my buffer has not changed.
any ideas or pointers to example code would be appreciated.
Oren

Answer 1

Hi,
i want to perform direct io reads from a specific disk
from within a kernel module. i tried to perform a
physio call, but although the function returns 0
(success) my buffer has not changed.
any ideas or pointers to example code would be
appreciated.
OrenIt's kinda non-trivial... physio() might be not good enough as if your disk is SCSI it won't perform sync I/O for you - you'd better use the aphysio(), or get the dev_ops of the disk and call it's strategy directly...
Do not forget to set completion (iodone) routine pointer in your buf structure - it'll be called upon I/O completion in asyncronous case. You might then wait on some CV in your I/O routine right after you've dispatched the strategy (either directly, or via aphysio), and in iodone() routine just signal the CV.
Hope this helps,
Ilya.