Re: [PATCH] fs/nfsd: Fix creation time serialization order

[Jeff Layton <jlayton@kernel.org>]

On Fri, 2023-06-23 at 17:09 -0400, tavianator@tavianator.com wrote:
> From: Tavian Barnes <tavianator@tavianator.com>
> 
> In nfsd4_encode_fattr(), TIME_CREATE was being written out after all
> other times.  However, they should be written out in an order that
> matches the bit flags in bmval1, which in this case are
> 
>     #define FATTR4_WORD1_TIME_ACCESS        (1UL << 15)
>     #define FATTR4_WORD1_TIME_CREATE        (1UL << 18)
>     #define FATTR4_WORD1_TIME_DELTA         (1UL << 19)
>     #define FATTR4_WORD1_TIME_METADATA      (1UL << 20)
>     #define FATTR4_WORD1_TIME_MODIFY        (1UL << 21)
> 
> so TIME_CREATE should come second.
> 
> I noticed this on a FreeBSD NFSv4.2 client, which supports creation
> times.  On this client, file times were weirdly permuted.  With this
> patch applied on the server, times looked normal on the client.
> 
> Fixes: e377a3e698fb ("nfsd: Add support for the birth time attribute")
> Link: https://unix.stackexchange.com/q/749605/56202
> Signed-off-by: Tavian Barnes <tavianator@tavianator.com>
> ---
>  fs/nfsd/nfs4xdr.c | 14 +++++++-------
>  1 file changed, 7 insertions(+), 7 deletions(-)
> 
> diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
> index 76db2fe29624..3037c5b0623e 100644
> --- a/fs/nfsd/nfs4xdr.c
> +++ b/fs/nfsd/nfs4xdr.c
> @@ -3354,6 +3354,13 @@ nfsd4_encode_fattr(struct xdr_stream *xdr, struct svc_fh *fhp,
>  		p = xdr_encode_hyper(p, (s64)stat.atime.tv_sec);
>  		*p++ = cpu_to_be32(stat.atime.tv_nsec);
>  	}
> +	if (bmval1 & FATTR4_WORD1_TIME_CREATE) {
> +		p = xdr_reserve_space(xdr, 12);
> +		if (!p)
> +			goto out_resource;
> +		p = xdr_encode_hyper(p, (s64)stat.btime.tv_sec);
> +		*p++ = cpu_to_be32(stat.btime.tv_nsec);
> +	}
>  	if (bmval1 & FATTR4_WORD1_TIME_DELTA) {
>  		p = xdr_reserve_space(xdr, 12);
>  		if (!p)
> @@ -3374,13 +3381,6 @@ nfsd4_encode_fattr(struct xdr_stream *xdr, struct svc_fh *fhp,
>  		p = xdr_encode_hyper(p, (s64)stat.mtime.tv_sec);
>  		*p++ = cpu_to_be32(stat.mtime.tv_nsec);
>  	}
> -	if (bmval1 & FATTR4_WORD1_TIME_CREATE) {
> -		p = xdr_reserve_space(xdr, 12);
> -		if (!p)
> -			goto out_resource;
> -		p = xdr_encode_hyper(p, (s64)stat.btime.tv_sec);
> -		*p++ = cpu_to_be32(stat.btime.tv_nsec);
> -	}
>  	if (bmval1 & FATTR4_WORD1_MOUNTED_ON_FILEID) {
>  		u64 ino = stat.ino;
>  

Reviewed-by: Jeff Layton <jlayton@kernel.org>