linux-kernel - Re: [Patch v2 12/15] CIFS: Pass page offset for encrypting

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Date:   Sat, 23 Jun 2018 22:28:43 -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 12/15] CIFS: Pass page offset for encrypting

On 5/30/2018 3:48 PM, Long Li wrote:
> From: Long Li <longli@...rosoft.com>
> 
> Encryption function needs to read data starting page offset from input
> buffer.
> 
> This doesn't affect decryption path since it allocates its own page
> buffers.
> 
> Signed-off-by: Long Li <longli@...rosoft.com>
> ---
>   fs/cifs/smb2ops.c | 20 +++++++++++++-------
>   1 file changed, 13 insertions(+), 7 deletions(-)
> 
> diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
> index 1fa1c29..38d19b6 100644
> --- a/fs/cifs/smb2ops.c
> +++ b/fs/cifs/smb2ops.c
> @@ -2189,9 +2189,10 @@ init_sg(struct smb_rqst *rqst, u8 *sign)
>   		smb2_sg_set_buf(&sg[i], rqst->rq_iov[i].iov_base,
>   						rqst->rq_iov[i].iov_len);
>   	for (j = 0; i < sg_len - 1; i++, j++) {
> -		unsigned int len = (j < rqst->rq_npages - 1) ? rqst->rq_pagesz
> -							: rqst->rq_tailsz;
> -		sg_set_page(&sg[i], rqst->rq_pages[j], len, 0);
> +		unsigned int len, offset;
> +
> +		rqst_page_get_length(rqst, j, &len, &offset);
> +		sg_set_page(&sg[i], rqst->rq_pages[j], len, offset);
>   	}
>   	smb2_sg_set_buf(&sg[sg_len - 1], sign, SMB2_SIGNATURE_SIZE);
>   	return sg;
> @@ -2332,6 +2333,7 @@ smb3_init_transform_rq(struct TCP_Server_Info *server, struct smb_rqst *new_rq,
>   		return rc;
>   
>   	new_rq->rq_pages = pages;
> +	new_rq->rq_offset = old_rq->rq_offset;
>   	new_rq->rq_npages = old_rq->rq_npages;
>   	new_rq->rq_pagesz = old_rq->rq_pagesz;
>   	new_rq->rq_tailsz = old_rq->rq_tailsz;
> @@ -2363,10 +2365,14 @@ smb3_init_transform_rq(struct TCP_Server_Info *server, struct smb_rqst *new_rq,
>   
>   	/* copy pages form the old */
>   	for (i = 0; i < npages; i++) {
> -		char *dst = kmap(new_rq->rq_pages[i]);
> -		char *src = kmap(old_rq->rq_pages[i]);
> -		unsigned int len = (i < npages - 1) ? new_rq->rq_pagesz :
> -							new_rq->rq_tailsz;
> +		char *dst, *src;
> +		unsigned int offset, len;
> +
> +		rqst_page_get_length(new_rq, i, &len, &offset);
> +
> +		dst = (char *) kmap(new_rq->rq_pages[i]) + offset;
> +		src = (char *) kmap(old_rq->rq_pages[i]) + offset;

Ouch! TWO kmap/kunmaps per page of data? Is there not already a kva,
at least for the destination (message)?

Tom.


> +
>   		memcpy(dst, src, len);
>   		kunmap(new_rq->rq_pages[i]);
>   		kunmap(old_rq->rq_pages[i]);
>