linux-kernel - Re: [PATCH 3/8] mm/swap: prevent concurrent swapon on the same S

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Message-ID: <CAL1ERfO2u838hnY2NVKVd7Tr_=2o=nVpBf_hTKGHms+QFGTFPQ@mail.gmail.com>
Date:	Fri, 18 Apr 2014 11:56:45 +0800
From:	Weijie Yang <weijie.yang.kh@...il.com>
To:	Hugh Dickins <hughd@...gle.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Weijie Yang <weijie.yang@...sung.com>,
	Minchan Kim <minchan@...nel.org>, shli@...nel.org,
	Bob Liu <bob.liu@...cle.com>,
	Seth Jennings <sjennings@...iantweb.net>,
	Heesub Shin <heesub.shin@...sung.com>, mquzik@...hat.com,
	Linux-MM <linux-mm@...ck.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/8] mm/swap: prevent concurrent swapon on the same
 S_ISBLK blockdev

On Tue, Feb 4, 2014 at 12:20 PM, Hugh Dickins <hughd@...gle.com> wrote:
> On Mon, 3 Feb 2014, Andrew Morton wrote:
>> On Mon, 27 Jan 2014 18:03:04 +0800 Weijie Yang <weijie.yang@...sung.com> wrote:
>>
>> > When swapon the same S_ISBLK blockdev concurrent, the allocated two
>> > swap_info could hold the same block_device, because claim_swapfile()
>> > allow the same holder(here, it is sys_swapon function).
>> >
>> > To prevent this situation, This patch adds swap_lock protect to ensure
>> > we can find this situation and return -EBUSY for one swapon call.
>> >
>> > As for S_ISREG swapfile, claim_swapfile() already prevent this scenario
>> > by holding inode->i_mutex.
>> >
>> > This patch is just for a rare scenario, aim to correct of code.
>> >
>>
>> hm, OK.  Would it be saner to pass a unique `holder' to
>> claim_swapfile()?  Say, `p'?
>>
>> Truly, I am fed up with silly swapon/swapoff races.  How often does
>> anyone call these things?  Let's slap a huge lock around the whole
>> thing and be done with it?
>
> That answer makes me sad: we can't be bothered to get it right,
> even when Weijie goes to the trouble of presenting a series to do so.
> But I sure don't deserve a vote until I've actually looked through it.
>

Hi,

This is a ping email. Could I get some options about these patch series?

Thanks.

> Hugh
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