Re: [PATCH 03/17] nfs: modify pg_test interface to return size_t

[Boaz Harrosh <bharrosh@panasas.com>]

On 04/23/2014 12:29 AM, Weston Andros Adamson wrote:
> This is a step toward allowing pg_test to inform the the
> coalescing code to reduce the size of requests so they may fit in
> whatever scheme the pg_test callback wants to define.
> 
> For now, just return the size of the request if there is space, or 0
> if there is not.  This shouldn't change any behavior as it acts
> the same as when the pg_test functions returned bool.
> 
> Signed-off-by: Weston Andros Adamson <dros@primarydata.com>
> ---
>  fs/nfs/blocklayout/blocklayout.c | 16 ++++++++++++----
>  fs/nfs/nfs4filelayout.c          | 12 +++++++-----
>  fs/nfs/objlayout/objio_osd.c     | 14 ++++++++++----
>  fs/nfs/pagelist.c                | 22 +++++++++++++++++++---
>  fs/nfs/pnfs.c                    | 12 +++++++++---
>  fs/nfs/pnfs.h                    |  3 ++-
>  include/linux/nfs_page.h         |  5 +++--
>  7 files changed, 62 insertions(+), 22 deletions(-)
> 
> diff --git a/fs/nfs/blocklayout/blocklayout.c b/fs/nfs/blocklayout/blocklayout.c
> index 65d849b..3867976 100644
> --- a/fs/nfs/blocklayout/blocklayout.c
> +++ b/fs/nfs/blocklayout/blocklayout.c
> @@ -1189,13 +1189,17 @@ bl_pg_init_read(struct nfs_pageio_descriptor *pgio, struct nfs_page *req)
>  		pnfs_generic_pg_init_read(pgio, req);
>  }
>  
> -static bool
> +/*
> + * Return 0 if @req cannot be coalesced into @pgio, otherwise return the number
> + * of bytes (maximum @req->wb_bytes) that can be coalesced.
> + */
> +static size_t
>  bl_pg_test_read(struct nfs_pageio_descriptor *pgio, struct nfs_page *prev,
>  		struct nfs_page *req)
>  {
>  	if (pgio->pg_dreq != NULL &&
>  	    !is_aligned_req(req, SECTOR_SIZE))
> -		return false;
> +		return 0;
>  
>  	return pnfs_generic_pg_test(pgio, prev, req);
>  }
> @@ -1241,13 +1245,17 @@ bl_pg_init_write(struct nfs_pageio_descriptor *pgio, struct nfs_page *req)
>  	}
>  }
>  
> -static bool
> +/*
> + * Return 0 if @req cannot be coalesced into @pgio, otherwise return the number
> + * of bytes (maximum @req->wb_bytes) that can be coalesced.
> + */
> +static size_t
>  bl_pg_test_write(struct nfs_pageio_descriptor *pgio, struct nfs_page *prev,
>  		 struct nfs_page *req)
>  {
>  	if (pgio->pg_dreq != NULL &&
>  	    !is_aligned_req(req, PAGE_CACHE_SIZE))
> -		return false;
> +		return 0;
>  
>  	return pnfs_generic_pg_test(pgio, prev, req);
>  }
> diff --git a/fs/nfs/nfs4filelayout.c b/fs/nfs/nfs4filelayout.c
> index b6fc8c1..dfc7282 100644
> --- a/fs/nfs/nfs4filelayout.c
> +++ b/fs/nfs/nfs4filelayout.c
> @@ -915,10 +915,10 @@ filelayout_alloc_lseg(struct pnfs_layout_hdr *layoutid,
>  /*
>   * filelayout_pg_test(). Called by nfs_can_coalesce_requests()
>   *
> - * return true  : coalesce page
> - * return false : don't coalesce page
> + * Return 0 if @req cannot be coalesced into @pgio, otherwise return the number
> + * of bytes (maximum @req->wb_bytes) that can be coalesced.
>   */
> -static bool
> +static size_t
>  filelayout_pg_test(struct nfs_pageio_descriptor *pgio, struct nfs_page *prev,
>  		   struct nfs_page *req)
>  {
> @@ -927,7 +927,7 @@ filelayout_pg_test(struct nfs_pageio_descriptor *pgio, struct nfs_page *prev,
>  
>  	if (!pnfs_generic_pg_test(pgio, prev, req) ||
>  	    !nfs_generic_pg_test(pgio, prev, req))
> -		return false;
> +		return 0;
>  
>  	p_stripe = (u64)req_offset(prev);
>  	r_stripe = (u64)req_offset(req);
> @@ -936,7 +936,9 @@ filelayout_pg_test(struct nfs_pageio_descriptor *pgio, struct nfs_page *prev,
>  	do_div(p_stripe, stripe_unit);
>  	do_div(r_stripe, stripe_unit);
>  
> -	return (p_stripe == r_stripe);
> +	if (p_stripe == r_stripe)
> +		return req->wb_bytes;
> +	return 0;
>  }
>  
>  static void
> diff --git a/fs/nfs/objlayout/objio_osd.c b/fs/nfs/objlayout/objio_osd.c
> index 5457745..c20352a 100644
> --- a/fs/nfs/objlayout/objio_osd.c
> +++ b/fs/nfs/objlayout/objio_osd.c
> @@ -564,14 +564,20 @@ int objio_write_pagelist(struct nfs_write_data *wdata, int how)
>  	return 0;
>  }
>  
> -static bool objio_pg_test(struct nfs_pageio_descriptor *pgio,
> +/*
> + * Return 0 if @req cannot be coalesced into @pgio, otherwise return the number
> + * of bytes (maximum @req->wb_bytes) that can be coalesced.
> + */
> +static size_t objio_pg_test(struct nfs_pageio_descriptor *pgio,
>  			  struct nfs_page *prev, struct nfs_page *req)
>  {
>  	if (!pnfs_generic_pg_test(pgio, prev, req))
> -		return false;
> +		return 0;
>  
> -	return pgio->pg_count + req->wb_bytes <=
> -			(unsigned long)pgio->pg_layout_private;
> +	if (pgio->pg_count + req->wb_bytes <=
> +	    (unsigned long)pgio->pg_layout_private)
> +		return req->wb_bytes;

nit

I hate this form please do an "else". This form I use when there
is no symmetry between the options, its like saying "I cut processing
short in this condition"

Thanks
Boaz

> +	return 0;
>  }
>  
>  static void objio_init_read(struct nfs_pageio_descriptor *pgio, struct nfs_page *req)
> diff --git a/fs/nfs/pagelist.c b/fs/nfs/pagelist.c
> index ecd34b7..3c35b9e 100644
> --- a/fs/nfs/pagelist.c
> +++ b/fs/nfs/pagelist.c
> @@ -277,7 +277,17 @@ nfs_wait_on_request(struct nfs_page *req)
>  			TASK_UNINTERRUPTIBLE);
>  }
>  
> -bool nfs_generic_pg_test(struct nfs_pageio_descriptor *desc, struct nfs_page *prev, struct nfs_page *req)
> +/*
> + * nfs_generic_pg_test - determine if requests can be coalesced
> + * @desc: pointer to descriptor
> + * @prev: previous request in desc, or NULL
> + * @req: this request
> + *
> + * Returns zero if @req can be coalesced into @desc, otherwise it returns
> + * the size of the request.
> + */
> +size_t nfs_generic_pg_test(struct nfs_pageio_descriptor *desc,
> +			   struct nfs_page *prev, struct nfs_page *req)
>  {
>  	/*
>  	 * FIXME: ideally we should be able to coalesce all requests
> @@ -289,7 +299,9 @@ bool nfs_generic_pg_test(struct nfs_pageio_descriptor *desc, struct nfs_page *pr
>  	if (desc->pg_bsize < PAGE_SIZE)
>  		return 0;
>  
> -	return desc->pg_count + req->wb_bytes <= desc->pg_bsize;
> +	if (desc->pg_count + req->wb_bytes <= desc->pg_bsize)
> +		return req->wb_bytes;
> +	return 0;
>  }
>  EXPORT_SYMBOL_GPL(nfs_generic_pg_test);
>  
> @@ -354,6 +366,8 @@ static bool nfs_can_coalesce_requests(struct nfs_page *prev,
>  				      struct nfs_page *req,
>  				      struct nfs_pageio_descriptor *pgio)
>  {
> +	size_t size;
> +
>  	if (!nfs_match_open_context(req->wb_context, prev->wb_context))
>  		return false;
>  	if (req->wb_context->dentry->d_inode->i_flock != NULL &&
> @@ -365,7 +379,9 @@ static bool nfs_can_coalesce_requests(struct nfs_page *prev,
>  		return false;
>  	if (req_offset(req) != req_offset(prev) + prev->wb_bytes)
>  		return false;
> -	return pgio->pg_ops->pg_test(pgio, prev, req);
> +	size = pgio->pg_ops->pg_test(pgio, prev, req);
> +	WARN_ON_ONCE(size && size != req->wb_bytes);
> +	return size > 0;
>  }
>  
>  /**
> diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
> index cb53d45..6201bf6 100644
> --- a/fs/nfs/pnfs.c
> +++ b/fs/nfs/pnfs.c
> @@ -1461,7 +1461,11 @@ pnfs_pageio_init_write(struct nfs_pageio_descriptor *pgio, struct inode *inode,
>  		nfs_pageio_init(pgio, inode, ld->pg_write_ops, compl_ops, server->wsize, ioflags);
>  }
>  
> -bool
> +/*
> + * Return 0 if @req cannot be coalesced into @pgio, otherwise return the number
> + * of bytes (maximum @req->wb_bytes) that can be coalesced.
> + */
> +size_t
>  pnfs_generic_pg_test(struct nfs_pageio_descriptor *pgio, struct nfs_page *prev,
>  		     struct nfs_page *req)
>  {
> @@ -1482,8 +1486,10 @@ pnfs_generic_pg_test(struct nfs_pageio_descriptor *pgio, struct nfs_page *prev,
>  	 * first byte that lies outside the pnfs_layout_range. FIXME?
>  	 *
>  	 */
> -	return req_offset(req) < end_offset(pgio->pg_lseg->pls_range.offset,
> -					 pgio->pg_lseg->pls_range.length);
> +	if (req_offset(req) < end_offset(pgio->pg_lseg->pls_range.offset,
> +					 pgio->pg_lseg->pls_range.length))
> +		return req->wb_bytes;
> +	return 0;
>  }
>  EXPORT_SYMBOL_GPL(pnfs_generic_pg_test);
>  
> diff --git a/fs/nfs/pnfs.h b/fs/nfs/pnfs.h
> index 0237939..0386d7c 100644
> --- a/fs/nfs/pnfs.h
> +++ b/fs/nfs/pnfs.h
> @@ -192,7 +192,8 @@ int pnfs_generic_pg_readpages(struct nfs_pageio_descriptor *desc);
>  void pnfs_generic_pg_init_write(struct nfs_pageio_descriptor *pgio,
>  			        struct nfs_page *req, u64 wb_size);
>  int pnfs_generic_pg_writepages(struct nfs_pageio_descriptor *desc);
> -bool pnfs_generic_pg_test(struct nfs_pageio_descriptor *pgio, struct nfs_page *prev, struct nfs_page *req);
> +size_t pnfs_generic_pg_test(struct nfs_pageio_descriptor *pgio,
> +			    struct nfs_page *prev, struct nfs_page *req);
>  void pnfs_set_lo_fail(struct pnfs_layout_segment *lseg);
>  struct pnfs_layout_segment *pnfs_layout_process(struct nfs4_layoutget *lgp);
>  void pnfs_free_lseg_list(struct list_head *tmp_list);
> diff --git a/include/linux/nfs_page.h b/include/linux/nfs_page.h
> index 905809d..214e098 100644
> --- a/include/linux/nfs_page.h
> +++ b/include/linux/nfs_page.h
> @@ -46,7 +46,8 @@ struct nfs_page {
>  struct nfs_pageio_descriptor;
>  struct nfs_pageio_ops {
>  	void	(*pg_init)(struct nfs_pageio_descriptor *, struct nfs_page *);
> -	bool	(*pg_test)(struct nfs_pageio_descriptor *, struct nfs_page *, struct nfs_page *);
> +	size_t	(*pg_test)(struct nfs_pageio_descriptor *, struct nfs_page *,
> +			   struct nfs_page *);
>  	int	(*pg_doio)(struct nfs_pageio_descriptor *);
>  };
>  
> @@ -89,7 +90,7 @@ extern	int nfs_pageio_add_request(struct nfs_pageio_descriptor *,
>  				   struct nfs_page *);
>  extern	void nfs_pageio_complete(struct nfs_pageio_descriptor *desc);
>  extern	void nfs_pageio_cond_complete(struct nfs_pageio_descriptor *, pgoff_t);
> -extern bool nfs_generic_pg_test(struct nfs_pageio_descriptor *desc,
> +extern size_t nfs_generic_pg_test(struct nfs_pageio_descriptor *desc,
>  				struct nfs_page *prev,
>  				struct nfs_page *req);
>  extern  int nfs_wait_on_request(struct nfs_page *);
>