linux-kernel - Re: [PATCH 0/6] Fix deadlock in ftl formating on mtd

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Date:   Tue, 15 Jun 2021 17:02:13 +0800
From:   Zhihao Cheng <chengzhihao1@...wei.com>
To:     Miquel Raynal <miquel.raynal@...tlin.com>
CC:     <richard@....at>, <vigneshr@...com>,
        <linux-mtd@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
        <yukuai3@...wei.com>
Subject: Re: [PATCH 0/6] Fix deadlock in ftl formating on mtd

在 2021/6/13 23:12, Miquel Raynal 写道:
> Hi Zhihao,
>
> Zhihao Cheng <chengzhihao1@...wei.com> wrote on Sun, 13 Jun 2021
> 19:30:29 +0800:
>
>> There is an AA-deadlock problem while formating mtd device to generate
>> a ftl device. Fix it by reverting "mtd: allow to unload the mtdtrans
>> module if its block devices aren't open" recommended in [1].
>>
> I understand that some fixes need to revert a couple of patches, but
> isn't reverting 6 commits from the v2.6.32 kernel a bit odd for that?
> At least, can you justify this choice? Are all these commits useless
> and buggy?
>
Hi Miquel,

This series of revert patches came from history commits which related 
with "mtd: allow to unload the mtdtrans module if its block devices 
aren't open". I admin it's a weird method and let's forget it.
After some local tests, I think we'd better reserve "mtd: allow to 
unload the mtdtrans module if its block devices aren't open" to support 
removing mtdblock module if no one takes it. But we may move get|put 
mtd_device into add|del_mtd_blktrans to solve deadlock problem, maybe we 
don't have to get_mtd_device each time open mtd block device in 
blktrans_open if we have called get_mtd_device() in 
add_mtd_blktrans_dev(). See v2 "mtd: mtd_blkdevs: Get|Put mtd_device in 
add|del_mtd_blktrans".

> Thanks,
> Miquèl
> .