Re: [Question] how to follow a symlink via a dentry?

From: Steven Rostedt
Date: Tue May 23 2006 - 16:55:35 EST

On Tue, 2006-05-23 at 10:08 -0700, Stephen Hemminger wrote:
> On Tue, 23 May 2006 12:56:03 -0400
> Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:
> > What is the best way from inside the kernel, to find the dentry that
> > another dentry points to via symlink?
> >
> > Scenario:
> >
> > I have a kobj of a device in the sysfs system. Inside a directory of
> > the kobj, is a symlink to another device I need to get. I can find the
> > dentry of the symlink, but I haven't found a good way to get to the
> > dentry of what the symlink points to.
> >
> > Is there a standard way to do this, or do I need to start hacking at the
> > follow_link of the sysfs directory to get what I want?
> >
> > Do I need to hack up something like page_readlink to get the path, and
> > then do vfs_follow_link to get the rest. Another thing is that I can't
> > rely on what current->fs points to.
> >
> > Thanks,
> >
> > -- Steve
> >
> Sysfs reflects kernel object linkage, you should not be using
> file access to find kernel objects. You should use the pointers
> instead.

What pointers are you talking about? Let me ask a better question. If
I have a pointer to an ide_drive_t or ide_driver_t or just the struct
device, how do I get to the block_device (bdev) that points to it?

So I have the /sys/block/hda/device object (which really is a symlink to
the /sys/devices/...) but I want to get to the object that
represents /sys/block/hda/device/block:hda which is also a symlink back
to /sys/block/hda. Right now the only way I know to do that is to follow
the sysfs.

-- Steve

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