From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: Minchan Kim <minchan@kernel.org>,
Junil Lee <junil0814.lee@lge.com>,
Andrew Morton <akpm@linux-foundation.org>,
ngupta@vflare.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org,
Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Subject: Re: [PATCH] zsmalloc: fix migrate_zspage-zs_free race condition
Date: Fri, 15 Jan 2016 12:30:15 +0900 [thread overview]
Message-ID: <20160115033015.GD1993@swordfish> (raw)
In-Reply-To: <20160115032712.GC1993@swordfish>
On (01/15/16 12:27), Sergey Senozhatsky wrote:
> > > @@ -1635,6 +1635,7 @@ static int migrate_zspage(struct zs_pool *pool, struct size_class *class,
> > > free_obj = obj_malloc(d_page, class, handle);
> > > zs_object_copy(free_obj, used_obj, class);
> > > index++;
> > > + free_obj |= BIT(HANDLE_PIN_BIT);
> > > record_obj(handle, free_obj);
> >
> > I think record_obj should store free_obj to *handle with masking off least bit.
> > IOW, how about this?
> >
> > record_obj(handle, obj)
> > {
> > *(unsigned long)handle = obj & ~(1<<HANDLE_PIN_BIT);
> > }
>
> [just a wild idea]
>
> or zs_free() can take spin_lock(&class->lock) earlier, it cannot free the
> object until the class is locked anyway, and migration is happening with
UNlocked
> the locked class. extending class->lock scope in zs_free() thus should
> not affect the perfomance. so it'll be either zs_free() is touching the
> object or the migration, not both.
-ss
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next prev parent reply other threads:[~2016-01-15 3:29 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-15 0:36 [PATCH] zsmalloc: fix migrate_zspage-zs_free race condition Junil Lee
2016-01-15 2:35 ` Minchan Kim
2016-01-15 3:27 ` Sergey Senozhatsky
2016-01-15 3:30 ` Sergey Senozhatsky [this message]
2016-01-15 4:49 ` Minchan Kim
2016-01-15 5:07 ` Sergey Senozhatsky
2016-01-19 15:47 ` Russell Knize
2016-01-20 7:00 ` Minchan Kim
2016-01-20 15:21 ` Russell Knize
2016-01-15 5:05 ` Minchan Kim
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