Re: [PATCH 2/2] NFS: Don't generate a GETATTR when opening an O_DIRECT file

[Chuck Lever <chuck.lever@oracle.com>]

On 02/11/2010 02:09 PM, Chuck Lever wrote:
> Close-to-open isn't needed for O_DIRECT files, since their data is
> never cached.  So if their attribute cache hasn't expired, skip the
> GETATTR.
>
> Note that fattr->time_start is required to be set correctly by the NFS
> direct I/O paths in order for this patch to work properly.
>
> Signed-off-by: Chuck Lever<chuck.lever@oracle.com>
> ---
>
>   fs/nfs/dir.c |   20 ++++++++++++++++----
>   1 files changed, 16 insertions(+), 4 deletions(-)
>
> diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
> index 3c7f03b..367302b 100644
> --- a/fs/nfs/dir.c
> +++ b/fs/nfs/dir.c
> @@ -709,6 +709,12 @@ static int nfs_is_exclusive_create(struct inode *dir, struct nameidata *nd)
>   	return nd&&  nfs_lookup_check_intent(nd, LOOKUP_EXCL);
>   }
>
> +static bool nfs_open_odirect(struct nameidata *nd)
> +{
> +	struct file *filp = nd->intent.open.file;
> +	return filp&&  (filp->f_flags&  O_DIRECT);
> +}
> +
>   /*
>    * Inode and filehandle revalidation for lookups.
>    *
> @@ -716,6 +722,9 @@ static int nfs_is_exclusive_create(struct inode *dir, struct nameidata *nd)
>    * or if the intent information indicates that we're about to open this
>    * particular file and the "nocto" mount flag is not set.
>    *
> + * O_DIRECT files have no locally cached data, so close-to-open checking
> + * isn't necessary.  However, their attributes must be revalidated if the
> + * cache has expired, mainly to catch the case where actimeo is zero.

Missing word...

+ * attribute cache has expired,

>    */
>   static inline
>   int nfs_lookup_verify_inode(struct inode *inode, struct nameidata *nd)
> @@ -730,12 +739,15 @@ int nfs_lookup_verify_inode(struct inode *inode, struct nameidata *nd)
>   			goto out_force;
>   		/* This is an open(2) */
>   		if (nfs_lookup_check_intent(nd, LOOKUP_OPEN) != 0&&
> -				!(server->flags&  NFS_MOUNT_NOCTO)&&
> -				(S_ISREG(inode->i_mode) ||
> -				 S_ISDIR(inode->i_mode)))
> -			goto out_force;
> +		    (S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode))) {
> +			if (nfs_open_odirect(nd))
> +				goto out_conditional;
> +			if (!(server->flags&  NFS_MOUNT_NOCTO))
> +				goto out_force;
> +		}
>   		return 0;
>   	}
> +out_conditional:
>   	return nfs_revalidate_inode(server, inode);
>   out_force:
>   	return __nfs_revalidate_inode(server, inode);
>
> --
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-- 
chuck[dot]lever[at]oracle[dot]com