Messages in this thread |  | | Subject | Re: [Patch v3 2/6] cifs: Allocate validate negotiation request through kmalloc | From | Tom Talpey <> | Date | Wed, 18 Apr 2018 10:07:52 -0400 |
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On 4/18/2018 9:08 AM, David Laight wrote: > From: Tom Talpey >> Sent: 18 April 2018 12:32 > ... >> On 4/17/2018 8:33 PM, Long Li wrote: >>> From: Long Li <longli@microsoft.com> >>> >>> The data buffer allocated on the stack can't be DMA'ed, and hence can't send >>> through RDMA via SMB Direct. >> >> This comment is confusing. Any registered memory can be DMA'd, need to >> state the reason for the choice here more clearly. > > The stack could be allocated with vmalloc(). > In which case the pages might not be physically contiguous and there is no > (sensible) call to get the physical address required by the dma controller > (or other bus master).
Memory registration does not requires pages to be physically contiguous. RDMA Regions can and do support very large physical page scatter/gather, and the adapter DMA's them readily. Is this the only reason?
Tom.
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