linux-kernel - Re: [PATCH-v2 2/9] target/pr: Use atomic bitop for se_dev_entry->pr

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Message-ID: <1432285557.898.28.camel@haakon3.risingtidesystems.com>
Date:	Fri, 22 May 2015 02:05:57 -0700
From:	"Nicholas A. Bellinger" <nab@...ux-iscsi.org>
To:	Christoph Hellwig <hch@....de>
Cc:	"Nicholas A. Bellinger" <nab@...erainc.com>,
	target-devel <target-devel@...r.kernel.org>,
	linux-scsi <linux-scsi@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Hannes Reinecke <hare@...e.de>,
	Sagi Grimberg <sagig@...lanox.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: Re: [PATCH-v2 2/9] target/pr: Use atomic bitop for
 se_dev_entry->pr_reg reservation check

On Fri, 2015-05-22 at 10:26 +0200, Christoph Hellwig wrote:
> On Fri, May 22, 2015 at 06:11:04AM +0000, Nicholas A. Bellinger wrote:
> > +	clear_bit(1, &orig->pr_reg);
> 
> Can you call it ->flags and give the bit a meaningful name?

The bit is signaling if se_dev_entry has a PR registration active.

I don't see how ->flags is a more meaningful name without other bits
defined.

> 
> > diff --git a/drivers/target/target_core_pr.c b/drivers/target/target_core_pr.c
> > index c0b593a..d29b39c 100644
> > --- a/drivers/target/target_core_pr.c
> > +++ b/drivers/target/target_core_pr.c
> > @@ -327,9 +327,13 @@ static int core_scsi3_pr_seq_non_holder(
> >  	int we = 0; /* Write Exclusive */
> >  	int legacy = 0; /* Act like a legacy device and return
> >  			 * RESERVATION CONFLICT on some CDBs */
> > +	bool registered = false;
> >  
> >  	rcu_read_lock();
> >  	se_deve = target_nacl_find_deve(nacl, cmd->orig_fe_lun);
> > +	if (se_deve)
> > +		registered = test_bit(1, &se_deve->pr_reg);
> > +	rcu_read_unlock();
> 
> It would be good to just sort out the registered and co variables
> here before the RCU changes, as in:
> 
> http://git.infradead.org/users/hch/scsi.git/commitdiff/6372d9f62c83acb30d051387c40deb4dbdcaa376

Why not just keep this patch squashed into the relevant commit in the
context of the larger RCU conversion..?

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