linux-kernel - Re: [PATCH v9 02/10] dax: Introduce holder for dax

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Message-ID: <76f5ed28-2df9-890e-0674-3ef2f18e2c2f@fujitsu.com>
Date:   Fri, 21 Jan 2022 09:26:52 +0800
From:   Shiyang Ruan <ruansy.fnst@...itsu.com>
To:     Christoph Hellwig <hch@...radead.org>,
        Dan Williams <dan.j.williams@...el.com>
CC:     "Darrick J. Wong" <djwong@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-xfs <linux-xfs@...r.kernel.org>,
        Linux NVDIMM <nvdimm@...ts.linux.dev>,
        Linux MM <linux-mm@...ck.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        david <david@...morbit.com>, Jane Chu <jane.chu@...cle.com>
Subject: Re: [PATCH v9 02/10] dax: Introduce holder for dax_device



在 2022/1/20 16:46, Christoph Hellwig 写道:
> On Wed, Jan 05, 2022 at 04:12:04PM -0800, Dan Williams wrote:
>> We ended up with explicit callbacks after hch balked at a notifier
>> call-chain, but I think we're back to that now. The partition mistake
>> might be unfixable, but at least bdev_dax_pgoff() is dead. Notifier
>> call chains have their own locking so, Ruan, this still does not need
>> to touch dax_read_lock().
> 
> I think we have a few options here:
> 
>   (1) don't allow error notifications on partitions.  And error return from
>       the holder registration with proper error handling in the file
>       system would give us that
>   (2) extent the holder mechanism to cover a range
>   (3) bite the bullet and create a new stacked dax_device for each
>       partition
> 
> I think (1) is the best option for now.  If people really do need
> partitions we'll have to go for (3)

Yes, I agree.  I'm doing it the first way right now.

I think that since we can use namespace to divide a big NVDIMM into 
multiple pmems, partition on a pmem seems not so meaningful.


--
Thanks,
Ruan.