linux-kernel - Re: [PATCH 25/20] sysfs: Only support removing emtpy sysfs directories.

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Message-ID: <Pine.LNX.4.44L0.0905281656590.4059-100000@iolanthe.rowland.org>
Date:	Thu, 28 May 2009 17:04:59 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	James Bottomley <James.Bottomley@...senPartnership.com>
cc:	Hannes Reinecke <hare@...e.de>, Kay Sievers <kay.sievers@...y.org>,
	SCSI development list <linux-scsi@...r.kernel.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Kernel development list <linux-kernel@...r.kernel.org>,
	Tejun Heo <tj@...nel.org>,
	Cornelia Huck <cornelia.huck@...ibm.com>,
	<linux-fsdevel@...r.kernel.org>,
	"Eric W. Biederman" <ebiederm@...stanetworks.com>
Subject: Re: [PATCH 25/20] sysfs: Only support removing emtpy sysfs  directories.

On Thu, 28 May 2009, James Bottomley wrote:

> > How so?  Why not unlink the target from the host's list when the 
> > device_del() call returns?  A new target can be created any time after 
> > that, since the old one is now completely invisible.
> 
> The answer to that one is several emails back: we need the target in the
> host list for the lifetime of the devices ... it's alterable, but even
> more auditing.

I don't recall you mentioning that the target had to be linked into the 
host's list for the lifetime of the devices; I thought you said merely 
that the target had to _exist_ for the lifetime of the devices.

Does it really need to be linked, or is existence of the structure 
sufficient?

Likewise, after a device is removed from visibility, does it need to 
remain linked into the host's and target's lists?

> > P.S.: Does scsi_target_reap() really ever get called in non-process
> > context?  I couldn't find any place where that might happen.
> 
> From the device release, which is done by last put, which could be I/O
> context.

But scsi_target_reap() isn't called directly from the device release.  
It's called from scsi_device_dev_release_usercontext().

And besides, in the patch I'm working on it isn't called from either of 
those places -- it's called from __scsi_remove_device().  So I'll go 
ahead and get rid of scsi_target_reap_usercontext().

Alan Stern

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