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Date: Fri, 23 Jan 2026 07:18:25 +0100
From: Christoph Hellwig <hch@lst.de>
To: Gao Xiang <hsiangkao@linux.alibaba.com>
Cc: Hongbo Li <lihongbo22@huawei.com>, chao@kernel.org, brauner@kernel.org,
	hch@lst.de, djwong@kernel.org, amir73il@gmail.com,
	linux-fsdevel@vger.kernel.org, linux-erofs@lists.ozlabs.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v16 04/10] erofs: add erofs_inode_set_aops helper to
 set the aops.
Message-ID: <20260123061825.GA25722@lst.de>
References: <20260122133718.658056-1-lihongbo22@huawei.com> <20260122133718.658056-5-lihongbo22@huawei.com> <b20b263d-132b-464e-8314-d3f795e5e582@linux.alibaba.com>
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User-Agent: Mutt/1.5.17 (2007-11-01)

On Thu, Jan 22, 2026 at 09:54:15PM +0800, Gao Xiang wrote:
>> @@ -455,6 +455,29 @@ static inline void *erofs_vm_map_ram(struct page **pages, unsigned int count)
>>   	return NULL;
>>   }
>>   +static inline int erofs_inode_set_aops(struct inode *inode,
>> +				       struct inode *realinode, bool no_fscache)
>> +{
>> +	if (erofs_inode_is_data_compressed(EROFS_I(realinode)->datalayout)) {
>> +		if (!IS_ENABLED(CONFIG_EROFS_FS_ZIP))
>> +			return -EOPNOTSUPP;
>> +		DO_ONCE_LITE_IF(realinode->i_blkbits != PAGE_SHIFT,
>> +			  erofs_info, realinode->i_sb,
>> +			  "EXPERIMENTAL EROFS subpage compressed block support in use. Use at your own risk!");
>> +		inode->i_mapping->a_ops = &z_erofs_aops;
>
> Is that available if CONFIG_EROFS_FS_ZIP is undefined?

z_erofs_aops is declared unconditionally, and the IS_ENABLED above
ensures the compiler will never generate a reference to it.

So this is fine, and a very usualy trick to make the code more
readable.