Re: [PATCH v16 04/10] erofs: add erofs_inode_set_aops helper to set the aops.

[Gao Xiang]

On 2026/1/23 14:18, Christoph Hellwig wrote:

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.

Yeah, I get your point, that is really helpful and I haven't
used that trick.

The other problem was the else part is incorrect, Hongbo,
how about applying the following code and resend the next
version, I will apply all patches later:

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;
                return 0;
        }
        inode->i_mapping->a_ops = &erofs_aops;
        if (IS_ENABLED(CONFIG_EROFS_FS_ONDEMAND) && !no_fscache &&
            erofs_is_fscache_mode(realinode->i_sb))
                inode->i_mapping->a_ops = &erofs_fscache_access_aops;
        if (IS_ENABLED(CONFIG_EROFS_FS_BACKED_BY_FILE) &&
            erofs_is_fileio_mode(EROFS_SB(realinode->i_sb)))
                inode->i_mapping->a_ops = &erofs_fileio_aops;
        return 0;
}

Thanks,
Gao Xiang