From: Michal Hocko <mhocko@kernel.org>
To: zijun_hu <zijun_hu@zoho.com>
Cc: zijun_hu@htc.com, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, tj@kernel.org,
akpm@linux-foundation.org, cl@linux.com
Subject: Re: [RFC PATCH 1/1] mm/percpu.c: fix memory leakage issue when allocate a odd alignment area
Date: Wed, 12 Oct 2016 08:53:32 +0200 [thread overview]
Message-ID: <20161012065332.GA9504@dhcp22.suse.cz> (raw)
In-Reply-To: <7649b844-cfe6-abce-148e-1e2236e7d443@zoho.com>
On Wed 12-10-16 08:28:17, zijun_hu wrote:
> On 2016/10/12 1:22, Michal Hocko wrote:
> > On Tue 11-10-16 21:24:50, zijun_hu wrote:
> >> From: zijun_hu <zijun_hu@htc.com>
> >>
> >> the LSB of a chunk->map element is used for free/in-use flag of a area
> >> and the other bits for offset, the sufficient and necessary condition of
> >> this usage is that both size and alignment of a area must be even numbers
> >> however, pcpu_alloc() doesn't force its @align parameter a even number
> >> explicitly, so a odd @align maybe causes a series of errors, see below
> >> example for concrete descriptions.
> >
> > Is or was there any user who would use a different than even (or power of 2)
> > alighment? If not is this really worth handling?
> >
>
> it seems only a power of 2 alignment except 1 can make sure it work very well,
> that is a strict limit, maybe this more strict limit should be checked
I fail to see how any other alignment would actually make any sense
what so ever. Look, I am not a maintainer of this code but adding a new
code to catch something that doesn't make any sense sounds dubious at
best to me.
I could understand this patch if you see a problem and want to prevent
it from repeating bug doing these kind of changes just in case sounds
like a bad idea.
--
Michal Hocko
SUSE Labs
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WARNING: multiple messages have this Message-ID (diff)
From: Michal Hocko <mhocko@kernel.org>
To: zijun_hu <zijun_hu@zoho.com>
Cc: zijun_hu@htc.com, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, tj@kernel.org,
akpm@linux-foundation.org, cl@linux.com
Subject: Re: [RFC PATCH 1/1] mm/percpu.c: fix memory leakage issue when allocate a odd alignment area
Date: Wed, 12 Oct 2016 08:53:32 +0200 [thread overview]
Message-ID: <20161012065332.GA9504@dhcp22.suse.cz> (raw)
In-Reply-To: <7649b844-cfe6-abce-148e-1e2236e7d443@zoho.com>
On Wed 12-10-16 08:28:17, zijun_hu wrote:
> On 2016/10/12 1:22, Michal Hocko wrote:
> > On Tue 11-10-16 21:24:50, zijun_hu wrote:
> >> From: zijun_hu <zijun_hu@htc.com>
> >>
> >> the LSB of a chunk->map element is used for free/in-use flag of a area
> >> and the other bits for offset, the sufficient and necessary condition of
> >> this usage is that both size and alignment of a area must be even numbers
> >> however, pcpu_alloc() doesn't force its @align parameter a even number
> >> explicitly, so a odd @align maybe causes a series of errors, see below
> >> example for concrete descriptions.
> >
> > Is or was there any user who would use a different than even (or power of 2)
> > alighment? If not is this really worth handling?
> >
>
> it seems only a power of 2 alignment except 1 can make sure it work very well,
> that is a strict limit, maybe this more strict limit should be checked
I fail to see how any other alignment would actually make any sense
what so ever. Look, I am not a maintainer of this code but adding a new
code to catch something that doesn't make any sense sounds dubious at
best to me.
I could understand this patch if you see a problem and want to prevent
it from repeating bug doing these kind of changes just in case sounds
like a bad idea.
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2016-10-12 6:53 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-11 13:24 [RFC PATCH 1/1] mm/percpu.c: fix memory leakage issue when allocate a odd alignment area zijun_hu
2016-10-11 13:24 ` zijun_hu
2016-10-11 17:22 ` Michal Hocko
2016-10-11 17:22 ` Michal Hocko
2016-10-12 0:28 ` zijun_hu
2016-10-12 0:28 ` zijun_hu
2016-10-12 6:53 ` Michal Hocko [this message]
2016-10-12 6:53 ` Michal Hocko
2016-10-12 7:20 ` zijun_hu
2016-10-12 7:20 ` zijun_hu
2016-10-12 7:24 ` zijun_hu
2016-10-12 7:24 ` zijun_hu
2016-10-12 8:25 ` Michal Hocko
2016-10-12 8:25 ` Michal Hocko
2016-10-12 8:44 ` zijun_hu
2016-10-12 8:44 ` zijun_hu
2016-10-12 9:54 ` Michal Hocko
2016-10-12 9:54 ` Michal Hocko
2016-10-12 9:59 ` zijun_hu
2016-10-12 9:59 ` zijun_hu
2016-10-13 23:31 ` Tejun Heo
2016-10-13 23:31 ` Tejun Heo
2016-10-14 0:23 ` zijun_hu
2016-10-14 0:23 ` zijun_hu
2016-10-14 0:28 ` Tejun Heo
2016-10-14 0:28 ` Tejun Heo
2016-10-14 0:58 ` zijun_hu
2016-10-14 0:58 ` zijun_hu
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