Re: [PATCH RESEND] svcrdma: handle rdma read with a non-zero initial page offset

[Doug Ledford <dledford@redhat.com>]

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On 10/07/2015 01:01 PM, J. Bruce Fields wrote:
> On Tue, Oct 06, 2015 at 01:44:25PM -0400, Doug Ledford wrote:
>> On 09/28/2015 05:46 PM, Steve Wise wrote:
>>> The server rdma_read_chunk_lcl() and rdma_read_chunk_frmr() functions
>>> were not taking into account the initial page_offset when determining
>>> the rdma read length.  This resulted in a read who's starting address
>>> and length exceeded the base/bounds of the frmr.
>>>
>>> Most work loads don't tickle this bug apparently, but one test hit it
>>> every time: building the linux kernel on a 16 core node with 'make -j
>>> 16 O=/mnt/0' where /mnt/0 is a ramdisk mounted via NFSRDMA.
>>>
>>> This bug seems to only be tripped with devices having small fastreg page
>>> list depths.  I didn't see it with mlx4, for instance.
>>
>> Bruce, what's you're take on this?  Do you want to push this through or
>> would you care if I push it through my tree?
> 
> Whoops, sorry, I meant to send a pull request for that last week.  Uh, I
> think I'll go ahead and do that now if it's OK with you.

Fine with me.  I was just trying to make sure it didn't get forgotten ;-)

> --b.
> 
>>
>>> Fixes: 0bf4828983df ('svcrdma: refactor marshalling logic')
>>> Signed-off-by: Steve Wise <swise@opengridcomputing.com>
>>> Tested-by: Chuck Lever <chuck.lever@oracle.com>
>>> ---
>>>
>>>  net/sunrpc/xprtrdma/svc_rdma_recvfrom.c |    6 ++++--
>>>  1 files changed, 4 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
>>> index cb51742..5f6ca47 100644
>>> --- a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
>>> +++ b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
>>> @@ -136,7 +136,8 @@ int rdma_read_chunk_lcl(struct svcxprt_rdma *xprt,
>>>  	ctxt->direction = DMA_FROM_DEVICE;
>>>  	ctxt->read_hdr = head;
>>>  	pages_needed = min_t(int, pages_needed, xprt->sc_max_sge_rd);
>>> -	read = min_t(int, pages_needed << PAGE_SHIFT, rs_length);
>>> +	read = min_t(int, (pages_needed << PAGE_SHIFT) - *page_offset,
>>> +		     rs_length);
>>>  
>>>  	for (pno = 0; pno < pages_needed; pno++) {
>>>  		int len = min_t(int, rs_length, PAGE_SIZE - pg_off);
>>> @@ -235,7 +236,8 @@ int rdma_read_chunk_frmr(struct svcxprt_rdma *xprt,
>>>  	ctxt->direction = DMA_FROM_DEVICE;
>>>  	ctxt->frmr = frmr;
>>>  	pages_needed = min_t(int, pages_needed, xprt->sc_frmr_pg_list_len);
>>> -	read = min_t(int, pages_needed << PAGE_SHIFT, rs_length);
>>> +	read = min_t(int, (pages_needed << PAGE_SHIFT) - *page_offset,
>>> +		     rs_length);
>>>  
>>>  	frmr->kva = page_address(rqstp->rq_arg.pages[pg_no]);
>>>  	frmr->direction = DMA_FROM_DEVICE;
>>>
>>> --
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>>
>>
>> -- 
>> Doug Ledford <dledford@redhat.com>
>>               GPG KeyID: 0E572FDD
>>
>>
> 
> 


-- 
Doug Ledford <dledford@redhat.com>
              GPG KeyID: 0E572FDD



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