Re: [PATCH v1 09/10] Move read list XDR round-up logic

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On Jan 9, 2015, at 3:14 PM, J. Bruce Fields <bfields@xxxxxxxxxxxx> wrote:

> On Fri, Jan 09, 2015 at 02:23:11PM -0500, Chuck Lever wrote:
>> Simpler approach, and this needs to be done before the tail is
>> copied to the end of the read list (pre-requisite for a subsequent
>> patch).
>> 
>> Fixes: e560e3b510d2 ("svcrdma: Add zero padding if the client... ")
> 
> Wait, does this actually fix a bug in that previous commit is or it
> just cleanup?

No change in behavior.

> If the latter, the "Fixes:.." line is confusing, just mention it in the
> text ("Simpler approach compared to the original attempt in
> e560e3b510d2...”).

OK.

> 
> --b.
> 
>> Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
>> ---
>> 
>> net/sunrpc/xprtrdma/svc_rdma_recvfrom.c |   37 ++++++++-----------------------
>> 1 files changed, 9 insertions(+), 28 deletions(-)
>> 
>> diff --git a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
>> index 36cf51a..a345cad 100644
>> --- a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
>> +++ b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
>> @@ -43,7 +43,6 @@
>> #include <linux/sunrpc/debug.h>
>> #include <linux/sunrpc/rpc_rdma.h>
>> #include <linux/spinlock.h>
>> -#include <linux/highmem.h>
>> #include <asm/unaligned.h>
>> #include <rdma/ib_verbs.h>
>> #include <rdma/rdma_cm.h>
>> @@ -434,6 +433,15 @@ static int rdma_read_chunks(struct svcxprt_rdma *xprt,
>> 		}
>> 	}
>> 
>> +	/* Read list may need XDR round-up (see RFC 5666, s. 3.7) */
>> +	if (page_offset & 3) {
>> +		u32 pad = 4 - (page_offset & 3);
>> +
>> +		head->arg.page_len += pad;
>> +		head->arg.len += pad;
>> +		head->arg.buflen += pad;
>> +	}
>> +
>> 	ret = 1;
>> 	head->position = position;
>> 
>> @@ -446,32 +454,6 @@ static int rdma_read_chunks(struct svcxprt_rdma *xprt,
>> 	return ret;
>> }
>> 
>> -/*
>> - * To avoid a separate RDMA READ just for a handful of zero bytes,
>> - * RFC 5666 section 3.7 allows the client to omit the XDR zero pad
>> - * in chunk lists.
>> - */
>> -static void
>> -rdma_fix_xdr_pad(struct xdr_buf *buf)
>> -{
>> -	unsigned int page_len = buf->page_len;
>> -	unsigned int size = (XDR_QUADLEN(page_len) << 2) - page_len;
>> -	unsigned int offset, pg_no;
>> -	char *p;
>> -
>> -	if (size == 0)
>> -		return;
>> -
>> -	pg_no = page_len >> PAGE_SHIFT;
>> -	offset = page_len & ~PAGE_MASK;
>> -	p = page_address(buf->pages[pg_no]);
>> -	memset(p + offset, 0, size);
>> -
>> -	buf->page_len += size;
>> -	buf->buflen += size;
>> -	buf->len += size;
>> -}
>> -
>> static int rdma_read_complete(struct svc_rqst *rqstp,
>> 			      struct svc_rdma_op_ctxt *head)
>> {
>> @@ -499,7 +481,6 @@ static int rdma_read_complete(struct svc_rqst *rqstp,
>> 	}
>> 
>> 	/* Point rq_arg.pages past header */
>> -	rdma_fix_xdr_pad(&head->arg);
>> 	rqstp->rq_arg.pages = &rqstp->rq_pages[head->hdr_count];
>> 	rqstp->rq_arg.page_len = head->arg.page_len;
>> 	rqstp->rq_arg.page_base = head->arg.page_base;
>> 
>> --
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> --
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--
Chuck Lever
chuck[dot]lever[at]oracle[dot]com



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