From: Seth Jennings <sjenning@linux.vnet.ibm.com>
To: Minchan Kim <minchan@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Andrew Morton <akpm@linux-foundation.org>,
Nitin Gupta <ngupta@vflare.org>,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
Dan Magenheimer <dan.magenheimer@oracle.com>,
Robert Jennings <rcj@linux.vnet.ibm.com>,
Jenifer Hopper <jhopper@us.ibm.com>, Mel Gorman <mgorman@suse.de>,
Johannes Weiner <jweiner@redhat.com>,
Rik van Riel <riel@redhat.com>,
Larry Woodman <lwoodman@redhat.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
devel@driverdev.osuosl.org
Subject: Re: [PATCHv2 1/9] staging: zsmalloc: add gfp flags to zs_create_pool
Date: Fri, 25 Jan 2013 09:07:47 -0600 [thread overview]
Message-ID: <51029FC3.4060402@linux.vnet.ibm.com> (raw)
In-Reply-To: <CAEwNFnDWpyvmN-fU=MczXKtcay6vMMCOOHUM2M09+wx7zOVxDQ@mail.gmail.com>
On 01/24/2013 07:33 PM, Minchan Kim wrote:
> Hi Seth, frontswap guys
>
> On Tue, Jan 8, 2013 at 5:24 AM, Seth Jennings
> <sjenning@linux.vnet.ibm.com> wrote:
>> zs_create_pool() currently takes a gfp flags argument
>> that is used when growing the memory pool. However
>> it is not used in allocating the metadata for the pool
>> itself. That is currently hardcoded to GFP_KERNEL.
>>
>> zswap calls zs_create_pool() at swapon time which is done
>> in atomic context, resulting in a "might sleep" warning.
>
> I didn't review this all series, really sorry but totday I saw Nitin
> added Acked-by so I'm afraid Greg might get it under my radar. I'm not
> strong against but I would like know why we should call frontswap_init
> under swap_lock? Is there special reason?
The call stack is:
SYSCALL_DEFINE2(swapon.. <-- swapon_mutex taken here
enable_swap_info() <-- swap_lock taken here
frontswap_init()
__frontswap_init()
zswap_frontswap_init()
zs_create_pool()
It isn't entirely clear to me why frontswap_init() is called under
lock. Then again, I'm not entirely sure what the swap_lock protects.
There are no comments near the swap_lock definition to tell me.
I would guess that the intent is to block any writes to the swap
device until frontswap_init() has completed.
Dan care to weigh in?
Seth
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WARNING: multiple messages have this Message-ID (diff)
From: Seth Jennings <sjenning@linux.vnet.ibm.com>
To: Minchan Kim <minchan@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Andrew Morton <akpm@linux-foundation.org>,
Nitin Gupta <ngupta@vflare.org>,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
Dan Magenheimer <dan.magenheimer@oracle.com>,
Robert Jennings <rcj@linux.vnet.ibm.com>,
Jenifer Hopper <jhopper@us.ibm.com>, Mel Gorman <mgorman@suse.de>,
Johannes Weiner <jweiner@redhat.com>,
Rik van Riel <riel@redhat.com>,
Larry Woodman <lwoodman@redhat.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
devel@driverdev.osuosl.org
Subject: Re: [PATCHv2 1/9] staging: zsmalloc: add gfp flags to zs_create_pool
Date: Fri, 25 Jan 2013 09:07:47 -0600 [thread overview]
Message-ID: <51029FC3.4060402@linux.vnet.ibm.com> (raw)
In-Reply-To: <CAEwNFnDWpyvmN-fU=MczXKtcay6vMMCOOHUM2M09+wx7zOVxDQ@mail.gmail.com>
On 01/24/2013 07:33 PM, Minchan Kim wrote:
> Hi Seth, frontswap guys
>
> On Tue, Jan 8, 2013 at 5:24 AM, Seth Jennings
> <sjenning@linux.vnet.ibm.com> wrote:
>> zs_create_pool() currently takes a gfp flags argument
>> that is used when growing the memory pool. However
>> it is not used in allocating the metadata for the pool
>> itself. That is currently hardcoded to GFP_KERNEL.
>>
>> zswap calls zs_create_pool() at swapon time which is done
>> in atomic context, resulting in a "might sleep" warning.
>
> I didn't review this all series, really sorry but totday I saw Nitin
> added Acked-by so I'm afraid Greg might get it under my radar. I'm not
> strong against but I would like know why we should call frontswap_init
> under swap_lock? Is there special reason?
The call stack is:
SYSCALL_DEFINE2(swapon.. <-- swapon_mutex taken here
enable_swap_info() <-- swap_lock taken here
frontswap_init()
__frontswap_init()
zswap_frontswap_init()
zs_create_pool()
It isn't entirely clear to me why frontswap_init() is called under
lock. Then again, I'm not entirely sure what the swap_lock protects.
There are no comments near the swap_lock definition to tell me.
I would guess that the intent is to block any writes to the swap
device until frontswap_init() has completed.
Dan care to weigh in?
Seth
next prev parent reply other threads:[~2013-01-25 15:09 UTC|newest]
Thread overview: 86+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-01-07 20:24 [PATCHv2 0/9] zswap: compressed swap caching Seth Jennings
2013-01-07 20:24 ` Seth Jennings
2013-01-07 20:24 ` [PATCHv2 1/9] staging: zsmalloc: add gfp flags to zs_create_pool Seth Jennings
2013-01-07 20:24 ` Seth Jennings
2013-01-25 0:08 ` Nitin Gupta
2013-01-25 0:08 ` Nitin Gupta
2013-01-25 1:33 ` Minchan Kim
2013-01-25 1:33 ` Minchan Kim
2013-01-25 15:07 ` Seth Jennings [this message]
2013-01-25 15:07 ` Seth Jennings
2013-01-25 15:56 ` Dan Magenheimer
2013-01-25 15:56 ` Dan Magenheimer
2013-01-28 2:59 ` Minchan Kim
2013-01-28 2:59 ` Minchan Kim
2013-01-30 16:11 ` Konrad Rzeszutek Wilk
2013-01-30 16:11 ` Konrad Rzeszutek Wilk
2013-01-31 5:21 ` Minchan Kim
2013-01-31 5:21 ` Minchan Kim
2013-01-25 21:26 ` Rik van Riel
2013-01-25 21:26 ` Rik van Riel
2013-01-07 20:24 ` [PATCHv2 2/9] staging: zsmalloc: remove unsed pool name Seth Jennings
2013-01-07 20:24 ` Seth Jennings
2013-01-25 0:09 ` Nitin Gupta
2013-01-25 0:09 ` Nitin Gupta
2013-01-25 21:50 ` Rik van Riel
2013-01-25 21:50 ` Rik van Riel
2013-01-07 20:24 ` [PATCHv2 3/9] staging: zsmalloc: add page alloc/free callbacks Seth Jennings
2013-01-07 20:24 ` Seth Jennings
2013-01-25 0:11 ` Nitin Gupta
2013-01-25 0:11 ` Nitin Gupta
2013-01-25 21:55 ` Rik van Riel
2013-01-25 21:55 ` Rik van Riel
2013-01-07 20:24 ` [PATCHv2 4/9] staging: zsmalloc: make CLASS_DELTA relative to PAGE_SIZE Seth Jennings
2013-01-07 20:24 ` Seth Jennings
2013-01-25 0:17 ` Nitin Gupta
2013-01-25 0:17 ` Nitin Gupta
2013-01-25 16:38 ` Seth Jennings
2013-01-25 16:38 ` Seth Jennings
2013-01-07 20:24 ` [PATCHv2 5/9] debugfs: add get/set for atomic types Seth Jennings
2013-01-07 20:24 ` Seth Jennings
2013-01-07 20:32 ` Greg Kroah-Hartman
2013-01-07 20:32 ` Greg Kroah-Hartman
2013-01-07 20:41 ` Seth Jennings
2013-01-07 20:41 ` Seth Jennings
2013-01-25 16:45 ` Seth Jennings
2013-01-25 16:45 ` Seth Jennings
2013-01-25 21:35 ` Greg Kroah-Hartman
2013-01-25 21:35 ` Greg Kroah-Hartman
2013-01-07 20:24 ` [PATCHv2 6/9] zsmalloc: promote to lib/ Seth Jennings
2013-01-07 20:24 ` Seth Jennings
2013-01-28 4:01 ` Minchan Kim
2013-01-28 4:01 ` Minchan Kim
2013-01-28 4:32 ` Minchan Kim
2013-01-28 4:32 ` Minchan Kim
2013-01-28 17:41 ` Seth Jennings
2013-01-28 17:41 ` Seth Jennings
2013-01-07 20:24 ` [PATCHv2 7/9] mm: break up swap_writepage() for frontswap backends Seth Jennings
2013-01-07 20:24 ` Seth Jennings
2013-01-28 4:22 ` Minchan Kim
2013-01-28 4:22 ` Minchan Kim
2013-01-28 17:26 ` Seth Jennings
2013-01-28 17:26 ` Seth Jennings
2013-01-28 23:46 ` Minchan Kim
2013-01-28 23:46 ` Minchan Kim
2013-01-07 20:24 ` [PATCHv2 8/9] zswap: add to mm/ Seth Jennings
2013-01-07 20:24 ` Seth Jennings
2013-01-08 17:15 ` Dave Hansen
2013-01-08 17:15 ` Dave Hansen
2013-01-08 17:54 ` Dan Magenheimer
2013-01-08 17:54 ` Dan Magenheimer
2013-01-25 22:44 ` Rik van Riel
2013-01-25 22:44 ` Rik van Riel
2013-01-25 23:15 ` Dan Magenheimer
2013-01-25 23:15 ` Dan Magenheimer
2013-01-28 15:27 ` Seth Jennings
2013-01-28 15:27 ` Seth Jennings
2013-01-29 10:21 ` Lord Glauber Costa of Sealand
2013-01-29 10:21 ` Lord Glauber Costa of Sealand
2013-02-07 16:13 ` Seth Jennings
2013-02-07 16:13 ` Seth Jennings
2013-02-11 19:13 ` Dan Magenheimer
2013-02-11 19:13 ` Dan Magenheimer
2013-01-07 20:24 ` [PATCHv2 9/9] zswap: add documentation Seth Jennings
2013-01-07 20:24 ` Seth Jennings
2013-01-22 18:10 ` [PATCHv2 0/9] zswap: compressed swap caching Seth Jennings
2013-01-22 18:10 ` Seth Jennings
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