As the title has said, I'm looking for how I can read/write blocks directly to disk in linux kernel space (bypassing the file system) and directly interact with block IO layer.
After reading through some kernel codes, I realize bio is the structure I should be using to achieve such goal in block IO layer. But I don't quite understand the structures of bio and haven't figure out how exactly I can do that.
Any helps? Thank you
If you're only doing something simple, you don't really need to mess with BIO. What you can do instead is to simply open the block device (/dev/whatever) as if it was a file. The kernel will do the right thing and will give you the "thin" wrapper for read/write operations.
In regard to opening the file from the kernel space, there are few questions here, already answered, like this one:
How to read/write files within a Linux kernel module?
If you want to do anything more fancy, you will have to study the sources of the FS drivers (in the fs/ subdirectory) to hunt for examples.