Re: [PATCH v2 5/5] nfs: don't clear STATX_ATIME from result_mask

[Trond Myklebust <trondmy@hammerspace.com>]

On Fri, 2018-10-19 at 14:20 +0200, Miklos Szeredi wrote:
> As per statx(2) man page only clear out flags that are unsupported by
> the
> fs or have an unrepresentable value.  Atime is supported by NFS as
> long as
> it's supported on the server.
> 
> So the STATX_ATIME flag should not be cleared in the result_mask if
> the
> operation was requested on a MNT_NOATIME or MNT_NODIRATIME mount.
> 
> This patch doesn't change the revalidation algorithm in any way, just
> the
> clearing of flags in stat->result_mask.
> 
> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
> Fixes: 9ccee940bd5b ("Support statx() mask and query flags
> parameters")
> Cc: Trond Myklebust <trond.myklebust@primarydata.com>
> ---
>  fs/nfs/inode.c | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
> 
> diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
> index b65aee481d13..34bb3e591709 100644
> --- a/fs/nfs/inode.c
> +++ b/fs/nfs/inode.c
> @@ -811,7 +811,7 @@ int nfs_getattr(const struct path *path, struct
> kstat *stat,
>  	if (!(request_mask &
> (STATX_MODE|STATX_NLINK|STATX_ATIME|STATX_CTIME|
>  					STATX_MTIME|STATX_UID|STATX_GID
> |
>  					STATX_SIZE|STATX_BLOCKS)))
> -		goto out_no_revalidate;
> +		goto out_no_update;
>  
>  	/* Check whether the cached attributes are stale */
>  	do_update |= force_sync || nfs_attribute_cache_expired(inode);
> @@ -833,9 +833,6 @@ int nfs_getattr(const struct path *path, struct
> kstat *stat,
>  			goto out;
>  	} else
>  		nfs_readdirplus_parent_cache_hit(path->dentry);
> -out_no_revalidate:
> -	/* Only return attributes that were revalidated. */
> -	stat->result_mask &= request_mask;
>  out_no_update:
>  	generic_fillattr(inode, stat);
>  	stat->ino = nfs_compat_user_ino64(NFS_FILEID(inode));

NACK.

When we don't revalidate the attribute, then the content of the field
contains junk values. The above code is very intentional.

-- 
Trond Myklebust
Linux NFS client maintainer, Hammerspace
trond.myklebust@hammerspace.com