Re: [PATCH] erofs: allow sharing page cache with the same aops only

[Hongbo Li]

On 2026/2/14 7:27, Gao Xiang wrote:
Hi Hongbo,

On Fri, Feb 13, 2026 at 07:33:45AM +0000, Hongbo Li wrote:
Inode with identical data but different @aops cannot be mixed
because the page cache is managed by different subsystems (e.g.,
@aops for compressed on-disk inodes cannot handle plain on-disk
inodes).

...

diff --git a/fs/erofs/inode.c b/fs/erofs/inode.c
index 4f86169c23f1..5b05272fd9c4 100644
--- a/fs/erofs/inode.c
+++ b/fs/erofs/inode.c
@@ -254,7 +254,8 @@ static int erofs_fill_inode(struct inode *inode)
        }
  
  	mapping_set_large_folios(inode->i_mapping);
-       return erofs_inode_set_aops(inode, inode, false);
+       inode->i_mapping->a_ops = erofs_get_aops(inode, false);
+       return IS_ERR(inode->i_mapping->a_ops) ? 
PTR_ERR(inode->i_mapping->a_ops) : 0;

I hope there is an aops variable instead of assigning
inode->i_mapping->a_ops directly.


Ok, thank you.
  }
  
  /*
diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
index d1634455e389..764e81b3bc08 100644
--- a/fs/erofs/internal.h
+++ b/fs/erofs/internal.h
@@ -471,26 +471,24 @@ 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)
+static inline const struct address_space_operations *
+erofs_get_aops(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;
+                       return ERR_PTR(-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;
+               return &z_erofs_aops;
        }
-       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;
+               return &erofs_fileio_aops;
+       if (IS_ENABLED(CONFIG_EROFS_FS_ONDEMAND) && !no_fscache &&
+           erofs_is_fscache_mode(realinode->i_sb))
+               return &erofs_fscache_access_aops;

Can you rearrange it as
        if (IS_ENABLED(CONFIG_EROFS_FS_ONDEMAND) && !no_fscache &&
            erofs_is_fscache_mode(realinode->i_sb))
                return &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 &erofs_aops;

Ok, they are equal. Since the EROFS in fscache mode can be fileio mode. 
And I will rearrange it in next version.

Thanks,
Hongbo

?

Thanks,
Gao Xiang