Re: [PATCH v2 1/3] ceph: handle InodeStat v8 versioned field in reply parsing

[Viacheslav Dubeyko <Slava.Dubeyko@ibm.com>]

On Tue, 2025-12-02 at 15:57 +0000, Alex Markuze wrote:
> Add forward-compatible handling for the new versioned field introduced
> in InodeStat v8. This patch only skips the field without using it,
> preparing for future protocol extensions.
> 
> The v8 encoding adds a versioned sub-structure that needs to be properly
> decoded and skipped to maintain compatibility with newer MDS versions.
> 
> Signed-off-by: Alex Markuze <amarkuze@redhat.com>
> ---
>  fs/ceph/mds_client.c | 20 ++++++++++++++++++++
>  1 file changed, 20 insertions(+)
> 
> diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
> index 1740047aef0f..d7d8178e1f9a 100644
> --- a/fs/ceph/mds_client.c
> +++ b/fs/ceph/mds_client.c
> @@ -231,6 +231,26 @@ static int parse_reply_info_in(void **p, void *end,
>  						      info->fscrypt_file_len, bad);
>  			}
>  		}
> +
> +		/*
> +		 * InodeStat encoding versions:
> +		 *   v1-v7: various fields added over time
> +		 *   v8: added optmetadata (versioned sub-structure containing
> +		 *       optional inode metadata like charmap for case-insensitive
> +		 *       filesystems). The kernel client doesn't support
> +		 *       case-insensitive lookups, so we skip this field.
> +		 *   v9: added subvolume_id (parsed below)
> +		 */
> +		if (struct_v >= 8) {
> +			u32 v8_struct_len;
> +
> +			/* skip optmetadata versioned sub-structure */
> +			ceph_decode_skip_8(p, end, bad);  /* struct_v */
> +			ceph_decode_skip_8(p, end, bad);  /* struct_compat */
> +			ceph_decode_32_safe(p, end, v8_struct_len, bad);
> +			ceph_decode_skip_n(p, end, v8_struct_len, bad);
> +		}
> +
>  		*p = end;
>  	} else {
>  		/* legacy (unversioned) struct */

Looks good.

Reviewed-by: Viacheslav Dubeyko <Slava.Dubeyko@ibm.com>

Thanks,
Slava.