Re: Accessing device information in REMOVE agent

[Greg KH <greg@kroah.com>]

On Sat, Nov 08, 2003 at 04:02:25PM +0300, Andrey Borzenkov wrote:
> I'd like to be notified when block device goes away (e.g. USB stick unplugged) 
> basically to look if device is in use and possibly initiate clean up. Block 
> hotplug currently is passing only DEVPATH; but it alone is not reliable way 
> to identify it; device may be used under alias names via symbolic links.

What do you mean?  DEVPATH is unique for that point in time.  There are
no alias's in sysfs.

> Is it safe to access /sys/$DEVPATH in REMOVE agent? Apparently hotplug is 
> called asynchronously i.e. it is possible that /sys entry is already removed?

The /sys entry is probably already removed, but if not, it will
disappear any second.  So no, it's not safe to try to access it, as it
will not work.

> Would it make sense to add device number? It seems to be natural native "block 
> device ID" :)

What "device number"?  The major/minor?  Why?  It's about as unique as
DEVPATH is for any point in time.

thanks,

greg k-h


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