On Wed, Dec 8, 2010 at 11:00 AM, sanoj <k.u.sanoj@xxxxxxxxx> wrote:
> Hello all,
> I want to track the read/write operations for a particular inode at the vfs
> layer.
> I added the following structure as a field to struct inode.
> struct meta_info
> {
> unsigned int read_count;
> unsigned int write_count;
> };
> This caused a problem in mounting the root device , what could be the cause
> ?
> Am i allowed modify the struct inode by adding a new field ?
> Also, i would like to know if there are any existing mechanisms that can
> help me track the workload .
> at various levels
> Thanks,
> sanoj
There are 2 instances of inode I believe.
One is the on disk layout, and one is the ram layout.
You can modify the ram layout to your hearts content, but the disk
layout you have to be very precise with.
The trouble is the ram instance will of course be free'd from time to
time, so you can't keep data in there forever.
I don't positively recall the lifetime rules for the ram instance, but
I think as long as a file is open, the inode is kept in RAM. I also
think there are ways to lock an inode in RAM if you need it RAM
resident over multiple open/close sessions.
Greg
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