linux-kernel - Re: [RFC PATCH kernel] block: initialize block_device::bd_bdi for bdev

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Message-ID: <86f99579-7213-0d86-6cdd-dbf0f1bc1385@ozlabs.ru>
Date:   Thu, 7 Jan 2021 19:24:21 +1100
From:   Alexey Kardashevskiy <aik@...abs.ru>
To:     Christoph Hellwig <hch@....de>
Cc:     Jan Kara <jack@...e.cz>, Alexander Viro <viro@...iv.linux.org.uk>,
        Hannes Reinecke <hare@...e.de>, Jens Axboe <axboe@...nel.dk>,
        Tejun Heo <tj@...nel.org>, linux-block@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH kernel] block: initialize block_device::bd_bdi for
 bdev_cache



On 07/01/2021 18:48, Christoph Hellwig wrote:
> On Thu, Jan 07, 2021 at 10:58:39AM +1100, Alexey Kardashevskiy wrote:
>>> And AFAICT the root inode on
>>> bdev superblock can get only to bdev_evict_inode() and bdev_free_inode().
>>> Looking at bdev_evict_inode() the only thing that's used there from struct
>>> block_device is really bd_bdi. bdev_free_inode() will also access
>>> bdev->bd_stats and bdev->bd_meta_info. So we need to at least initialize
>>> these to NULL as well.
>>
>> These are all NULL.
>>
>>> IMO the most logical place for all these
>>> initializations is in bdev_alloc_inode()...
>>
>>
>> This works. We can also check for NULL where it crashes. But I do not know
>> the code to make an informed decision...
> 
> The root inode is the special case, so I think moving the the initializers
> for everything touched in ->evict_inode and ->free_inode to
> bdev_alloc_inode makes most sense.
> 
> Alexey, do you want to respin or should I send a patch?

I really prefer you doing this as you will most likely end up fixing the 
commit log anyway :) Thanks,


-- 
Alexey