Re: [PATCH] erofs: support SEEK_HOLE/SEEK_DATA in inode_share mode

[Gao Xiang]

Hi Jingbo,

On Tue, Aug 18, 2026 at 07:37:13PM +0800, Jingbo Xu wrote:
> When inode_share is enabled, erofs_ishare_fops.llseek falls back to
> generic_file_llseek, which treats the whole file as data and always
> returns i_size for SEEK_HOLE, hiding real holes in sparse files.
> 
> Switch it to erofs_file_llseek instead.  For user files f_mapping->host
> is always the real erofs inode, so SEEK_HOLE/SEEK_DATA resolve the
> per-file on-disk layout via iomap_seek_hole()/iomap_seek_data().
> 
> Reported-by: Yuanhe Shu <xiangzao@xxxxxxxxxxxxxxxxx>
> Signed-off-by: Jingbo Xu <jefflexu@xxxxxxxxxxxxxxxxx>
> ---
>  fs/erofs/data.c     | 2 +-
>  fs/erofs/internal.h | 2 ++
>  fs/erofs/ishare.c   | 2 +-
>  3 files changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/erofs/data.c b/fs/erofs/data.c
> index d2f01245ee79..09d668deb86d 100644
> --- a/fs/erofs/data.c
> +++ b/fs/erofs/data.c
> @@ -509,7 +509,7 @@ static int erofs_file_mmap_prepare(struct vm_area_desc *desc)
>  #define erofs_file_mmap_prepare	generic_file_readonly_mmap_prepare
>  #endif
>  
> -static loff_t erofs_file_llseek(struct file *file, loff_t offset, int whence)
> +loff_t erofs_file_llseek(struct file *file, loff_t offset, int whence)
>  {
>  	struct inode *inode = file->f_mapping->host;
>  	const struct iomap_ops *ops = &erofs_iomap_ops;
> diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
> index 57bd21859c65..3263c11d714c 100644
> --- a/fs/erofs/internal.h
> +++ b/fs/erofs/internal.h
> @@ -528,6 +528,8 @@ static inline struct inode *erofs_real_inode(struct inode *inode, bool *need_ipu
>  }
>  #endif
>  
> +loff_t erofs_file_llseek(struct file *file, loff_t offset, int whence);
> +

Could you move this line below erofs_fiemap()? I hope all declarations
in data.c are closer.

Otherwise it looks good to me,
Reviewed-by: Gao Xiang <xiang@xxxxxxxxxx>

Also could you help write a test for this functionality too?

Thanks,
Gao Xiang