linux-kernel - Re: [Patch v2 06/15] CIFS: Introduce helper function to get page offset and length in smb

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Date:   Sat, 23 Jun 2018 22:09:14 -0400
From:   Tom Talpey <tom@...pey.com>
To:     longli@...rosoft.com, Steve French <sfrench@...ba.org>,
        linux-cifs@...r.kernel.org, samba-technical@...ts.samba.org,
        linux-kernel@...r.kernel.org, linux-rdma@...r.kernel.org
Subject: Re: [Patch v2 06/15] CIFS: Introduce helper function to get page
 offset and length in smb_rqst

On 5/30/2018 3:47 PM, Long Li wrote:
> From: Long Li <longli@...rosoft.com>
> 
> Introduce a function rqst_page_get_length to return the page offset and
> length for a given page in smb_rqst. This function is to be used by
> following patches.
> 
> Signed-off-by: Long Li <longli@...rosoft.com>
> ---
>   fs/cifs/cifsproto.h |  3 +++
>   fs/cifs/misc.c      | 17 +++++++++++++++++
>   2 files changed, 20 insertions(+)
> 
> diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h
> index 7933c5f..89dda14 100644
> --- a/fs/cifs/cifsproto.h
> +++ b/fs/cifs/cifsproto.h
> @@ -557,4 +557,7 @@ int cifs_alloc_hash(const char *name, struct crypto_shash **shash,
>   		    struct sdesc **sdesc);
>   void cifs_free_hash(struct crypto_shash **shash, struct sdesc **sdesc);
>   
> +extern void rqst_page_get_length(struct smb_rqst *rqst, unsigned int page,
> +				unsigned int *len, unsigned int *offset);
> +
>   #endif			/* _CIFSPROTO_H */
> diff --git a/fs/cifs/misc.c b/fs/cifs/misc.c
> index 96849b5..e951417 100644
> --- a/fs/cifs/misc.c
> +++ b/fs/cifs/misc.c
> @@ -905,3 +905,20 @@ cifs_free_hash(struct crypto_shash **shash, struct sdesc **sdesc)
>   		crypto_free_shash(*shash);
>   	*shash = NULL;
>   }
> +
> +/**
> + * rqst_page_get_length - obtain the length and offset for a page in smb_rqst
> + * Input: rqst - a smb_rqst, page - a page index for rqst
> + * Output: *len - the length for this page, *offset - the offset for this page
> + */
> +void rqst_page_get_length(struct smb_rqst *rqst, unsigned int page,
> +				unsigned int *len, unsigned int *offset)
> +{
> +	*len = rqst->rq_pagesz;
> +	*offset = (page == 0) ? rqst->rq_offset : 0;

Really? Page 0 always has a zero offset??

> +
> +	if (rqst->rq_npages == 1 || page == rqst->rq_npages-1)
> +		*len = rqst->rq_tailsz;
> +	else if (page == 0)
> +		*len = rqst->rq_pagesz - rqst->rq_offset;
> +}
> 

This subroutine does what patch 5 does inline. Why not push this patch
up in the sequence and use the helper?

Tom.