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Subject: Re: [Patch v2 04/15] CIFS: Add support for direct pages in wdata
To:     longli@microsoft.com, Steve French <sfrench@samba.org>,
        linux-cifs@vger.kernel.org, samba-technical@lists.samba.org,
        linux-kernel@vger.kernel.org, linux-rdma@vger.kernel.org
References: <20180530194807.31657-1-longli@linuxonhyperv.com>
 <20180530194807.31657-5-longli@linuxonhyperv.com>
From:   Tom Talpey <tom@talpey.com>
Message-ID: <4edad13c-e257-ff1c-223a-324f484a936a@talpey.com>
Date:   Sat, 23 Jun 2018 22:01:59 -0400
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On 5/30/2018 3:47 PM, Long Li wrote:
> From: Long Li <longli@microsoft.com>
> 
> Add a function to allocate wdata without allocating pages for data
> transfer. This gives the caller an option to pass a number of pages that
> point to the data buffer to write to.
> 
> wdata is reponsible for free those pages after it's done.

Same comment as for the earlier patch. "Caller" is responsible for
"freeing" those pages? Confusing, as worded.

> 
> Signed-off-by: Long Li <longli@microsoft.com>
> ---
>   fs/cifs/cifsglob.h  |  2 +-
>   fs/cifs/cifsproto.h |  2 ++
>   fs/cifs/cifssmb.c   | 17 ++++++++++++++---
>   3 files changed, 17 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
> index 56864a87..7f62c98 100644
> --- a/fs/cifs/cifsglob.h
> +++ b/fs/cifs/cifsglob.h
> @@ -1205,7 +1205,7 @@ struct cifs_writedata {
>   	unsigned int			tailsz;
>   	unsigned int			credits;
>   	unsigned int			nr_pages;
> -	struct page			*pages[];
> +	struct page			**pages;

Also same comment as for earlier patch, these are syntactically
equivalent and maybe not needed to change.

>   };
>   
>   /*
> diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h
> index 1f27d8e..7933c5f 100644
> --- a/fs/cifs/cifsproto.h
> +++ b/fs/cifs/cifsproto.h
> @@ -533,6 +533,8 @@ int cifs_async_writev(struct cifs_writedata *wdata,
>   void cifs_writev_complete(struct work_struct *work);
>   struct cifs_writedata *cifs_writedata_alloc(unsigned int nr_pages,
>   						work_func_t complete);
> +struct cifs_writedata *cifs_writedata_direct_alloc(struct page **pages,
> +						work_func_t complete);
>   void cifs_writedata_release(struct kref *refcount);
>   int cifs_query_mf_symlink(unsigned int xid, struct cifs_tcon *tcon,
>   			  struct cifs_sb_info *cifs_sb,
> diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c
> index c8e4278..5aca336 100644
> --- a/fs/cifs/cifssmb.c
> +++ b/fs/cifs/cifssmb.c
> @@ -1952,6 +1952,7 @@ cifs_writedata_release(struct kref *refcount)
>   	if (wdata->cfile)
>   		cifsFileInfo_put(wdata->cfile);
>   
> +	kvfree(wdata->pages);
>   	kfree(wdata);
>   }
>   
> @@ -2075,12 +2076,22 @@ cifs_writev_complete(struct work_struct *work)
>   struct cifs_writedata *
>   cifs_writedata_alloc(unsigned int nr_pages, work_func_t complete)
>   {
> +	struct page **pages =
> +		kzalloc(sizeof(struct page *) * nr_pages, GFP_NOFS);

Why do you do a GFP_NOFS here but GFP_KERNEL in the earlier patch?

> +	if (pages)
> +		return cifs_writedata_direct_alloc(pages, complete);
> +
> +	return NULL;
> +}
> +
> +struct cifs_writedata *
> +cifs_writedata_direct_alloc(struct page **pages, work_func_t complete)
> +{
>   	struct cifs_writedata *wdata;
>   
> -	/* writedata + number of page pointers */
> -	wdata = kzalloc(sizeof(*wdata) +
> -			sizeof(struct page *) * nr_pages, GFP_NOFS);
> +	wdata = kzalloc(sizeof(*wdata), GFP_NOFS);
>   	if (wdata != NULL) {
> +		wdata->pages = pages;
>   		kref_init(&wdata->refcount);
>   		INIT_LIST_HEAD(&wdata->list);
>   		init_completion(&wdata->done);
>