linux-kernel - Re: [PATCH v2 2/2] erofs: use get_tree_bdev

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Message-ID: <8a40d27c-28f1-467b-9a9e-359b36ee5e33@linux.alibaba.com>
Date: Wed, 9 Oct 2024 15:37:04 +0800
From: Gao Xiang <hsiangkao@...ux.alibaba.com>
To: Christoph Hellwig <hch@...radead.org>
Cc: Christian Brauner <brauner@...nel.org>,
 Alexander Viro <viro@...iv.linux.org.uk>, Jan Kara <jack@...e.cz>,
 Allison Karlitskaya <allison.karlitskaya@...hat.com>,
 Chao Yu <chao@...nel.org>, LKML <linux-kernel@...r.kernel.org>,
 linux-fsdevel@...r.kernel.org, linux-erofs@...ts.ozlabs.org
Subject: Re: [PATCH v2 2/2] erofs: use get_tree_bdev_flags() to avoid
 misleading messages

Hi Christoph,

On 2024/10/9 15:31, Christoph Hellwig wrote:
> On Wed, Oct 09, 2024 at 11:31:51AM +0800, Gao Xiang wrote:
>> Users can pass in an arbitrary source path for the proper type of
>> a mount then without "Can't lookup blockdev" error message.
>>
>> Reported-by: Allison Karlitskaya <allison.karlitskaya@...hat.com>
>> Closes: https://lore.kernel.org/r/CAOYeF9VQ8jKVmpy5Zy9DNhO6xmWSKMB-DO8yvBB0XvBE7=3Ugg@mail.gmail.com
>> Signed-off-by: Gao Xiang <hsiangkao@...ux.alibaba.com>
>> ---
>> changes since v1:
>>   - use new get_tree_bdev_flags().
>>
>>   fs/erofs/super.c | 4 +++-
>>   1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/fs/erofs/super.c b/fs/erofs/super.c
>> index 666873f745da..b89836a8760d 100644
>> --- a/fs/erofs/super.c
>> +++ b/fs/erofs/super.c
>> @@ -705,7 +705,9 @@ static int erofs_fc_get_tree(struct fs_context *fc)
>>   	if (IS_ENABLED(CONFIG_EROFS_FS_ONDEMAND) && sbi->fsid)
>>   		return get_tree_nodev(fc, erofs_fc_fill_super);
>>   
>> -	ret = get_tree_bdev(fc, erofs_fc_fill_super);
>> +	ret = get_tree_bdev_flags(fc, erofs_fc_fill_super,
>> +		IS_ENABLED(CONFIG_EROFS_FS_BACKED_BY_FILE) ?
>> +			GET_TREE_BDEV_QUIET_LOOKUP : 0);
> 
> Why not pass it unconditionally and provide your own more useful
> error message at the end of the function if you could not find any
> source?

My own (potential) concern is that if CONFIG_EROFS_FS_BACKED_BY_FILE
is off, EROFS should just behave as other pure bdev fses since I'm
not sure if some userspace program really relies on
"Can't lookup blockdev" behavior.

.. Yet that is just my own potential worry anyway.

Thanks,
Gao Xiang