linux-kernel - Re: [PATCH v1 2/2] zram: remove init_lock in zram_make

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Mon, 2 Feb 2015 10:59:40 +0900
From:	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:	Minchan Kim <minchan@...nel.org>
Cc:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Linux-MM <linux-mm@...ck.org>, Nitin Gupta <ngupta@...are.org>,
	Jerome Marchand <jmarchan@...hat.com>,
	Ganesh Mahendran <opensource.ganesh@...il.com>
Subject: Re: [PATCH v1 2/2] zram: remove init_lock in zram_make_request

On (02/02/15 10:43), Minchan Kim wrote:
> >  static inline int init_done(struct zram *zram)
> >  {
> > -	return zram->meta != NULL;
> > +	return atomic_read(&zram->refcount);
> 
> As I said previous mail, it could make livelock so I want to use disksize
> in here to prevent further I/O handling.

just as I said in my previous email -- is this live lock really possible?
we need to umount device to continue with reset. and umount will kill IOs out
of our way.

the other reset caller is  __exit zram_exit(). but once again, I don't
expect this function being executed on mounted device and module being
in use.


> > +static inline void zram_put(struct zram *zram)
> > +{
> > +	if (atomic_dec_and_test(&zram->refcount))
> > +		complete(&zram->io_done);
> > +}
> 
> Although I suggested this complete, it might be rather overkill(pz,
> understand me it was work in midnight. :))
> Instead, we could use just atomic_dec in here and
> use wait_event(event, atomic_read(&zram->refcount) == 0) in reset.
> 

yes, I think it can do the trick.

	-ss
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/