linux-kernel - Re: [PATCH v2 5/5] nfs: don't clear STATX_ATIME from result

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Message-ID: <2ca365ec330cf918188e8c47b26e741073382d9d.camel@primarydata.com>
Date:   Fri, 19 Oct 2018 15:52:37 +0000
From:   Trond Myklebust <trondmy@...merspace.com>
To:     "mszeredi@...hat.com" <mszeredi@...hat.com>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>
CC:     "amir73il@...il.com" <amir73il@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "adilger@...ger.ca" <adilger@...ger.ca>,
        "mtk.manpages@...il.com" <mtk.manpages@...il.com>,
        "fw@...eb.enyo.de" <fw@...eb.enyo.de>,
        "linux-api@...r.kernel.org" <linux-api@...r.kernel.org>,
        "dhowells@...hat.com" <dhowells@...hat.com>
Subject: Re: [PATCH v2 5/5] nfs: don't clear STATX_ATIME from result_mask

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@...hat.com>
> Fixes: 9ccee940bd5b ("Support statx() mask and query flags
> parameters")
> Cc: Trond Myklebust <trond.myklebust@...marydata.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@...merspace.com