Re: [PATCH 07/10] pnfs-submit: avoid race handling return on close

[Benny Halevy <bhalevy@panasas.com>]

On Jun. 14, 2010, 21:46 -0400, Fred Isaman <iisaman@netapp.com> wrote:
> This prepares for the next patch.
> 
> NOTE this doesn't really fix any current race, since
> layout going to NULL is OK.  But layout changing from NULL to nonNULL
> is a real race that is not fixed
> 
> Signed-off-by: Fred Isaman <iisaman@netapp.com>
> ---
>  fs/nfs/nfs4state.c        |    5 +++--
>  fs/nfs/pnfs.c             |   11 +++++++++++
>  include/linux/nfs4_pnfs.h |    2 ++
>  3 files changed, 16 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
> index d5144bd..8a7a64c 100644
> --- a/fs/nfs/nfs4state.c
> +++ b/fs/nfs/nfs4state.c
> @@ -594,11 +594,12 @@ static void __nfs4_close(struct path *path, struct nfs4_state *state,
>  	} else {
>  #ifdef CONFIG_NFS_V4_1
>  		struct nfs_inode *nfsi = NFS_I(state->inode);
> +		int roc = nfs4_roc_iomode(nfsi);
>  
> -		if (has_layout(nfsi) && nfsi->layout.roc_iomode) {
> +		if (roc) {
>  			struct nfs4_pnfs_layout_segment range;
>  
> -			range.iomode = nfsi->layout.roc_iomode;
> +			range.iomode = roc;
>  			range.offset = 0;
>  			range.length = NFS4_MAX_UINT64;
>  			pnfs_return_layout(state->inode, &range, NULL,
> diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
> index 6def09c..bd11ec7 100644
> --- a/fs/nfs/pnfs.c
> +++ b/fs/nfs/pnfs.c
> @@ -321,6 +321,17 @@ pnfs_unregister_layoutdriver(struct pnfs_layoutdriver_type *ld_type)
>  #define BUG_ON_UNLOCKED_LO(lo) do {} while (0)
>  #endif /* CONFIG_SMP */
>  
> +int nfs4_roc_iomode(struct nfs_inode *nfsi)
> +{
> +	int rv = 0;
> +
> +	spin_lock(&pnfs_spinlock);

Why take the global lock rather than nfsi->lo_lock?

Benny

> +	if (has_layout(nfsi))
> +		rv = nfsi->layout.roc_iomode;
> +	spin_unlock(&pnfs_spinlock);
> +	return rv;
> +}
> +
>  static inline void
>  get_layout(struct pnfs_layout_type *lo)
>  {
> diff --git a/include/linux/nfs4_pnfs.h b/include/linux/nfs4_pnfs.h
> index 0eb9b16..2ea131f 100644
> --- a/include/linux/nfs4_pnfs.h
> +++ b/include/linux/nfs4_pnfs.h
> @@ -86,6 +86,8 @@ layoutcommit_needed(struct nfs_inode *nfsi)
>  	return test_bit(NFS_INO_LAYOUTCOMMIT, &nfsi->pnfs_layout_state);
>  }
>  
> +int nfs4_roc_iomode(struct nfs_inode *nfs);
> +
>  #else /* CONFIG_NFS_V4_1 */
>  
>  static inline bool