linux-kernel - Re: [PATCH v16 04/10] erofs: add erofs_inode_set

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Message-ID: <20260123061825.GA25722@lst.de>
Date: Fri, 23 Jan 2026 07:18:25 +0100
From: Christoph Hellwig <hch@....de>
To: Gao Xiang <hsiangkao@...ux.alibaba.com>
Cc: Hongbo Li <lihongbo22@...wei.com>, chao@...nel.org, brauner@...nel.org,
	hch@....de, djwong@...nel.org, amir73il@...il.com,
	linux-fsdevel@...r.kernel.org, linux-erofs@...ts.ozlabs.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v16 04/10] erofs: add erofs_inode_set_aops helper to
 set the aops.

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.