From: Christoph Hellwig <hch@lst.de>
To: Logan Gunthorpe <logang@deltatee.com>
Cc: James Smart <james.smart@broadcom.com>,
linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org,
Christoph Hellwig <hch@lst.de>, Sagi Grimberg <sagi@grimberg.me>
Subject: Re: [PATCH 4/4] nvmet-fc: Use new SGL alloc/free helper for requests
Date: Thu, 29 Mar 2018 20:15:45 +0200 [thread overview]
Message-ID: <20180329181545.GA16116@lst.de> (raw)
In-Reply-To: <bd62c2e6-558c-e314-177f-c95cf842c741@deltatee.com>
On Thu, Mar 29, 2018 at 11:02:10AM -0600, Logan Gunthorpe wrote:
> Per the bug in the previous patch, I don't think that was ever a valid
> assumption. It doesn't have anything to do with the sgl_alloc change
> either. The dma_map interface is allowed to merge SGLs and that's why it
> can return fewer nents than it was passed. I'm not sure how many or
> which DMA ops actually do this which is why it hasn't actually
> manifested itself as a bug; but it is part of how the interface is
> specified to work.
Most iommus can, it just is very unlikely do happen in block drivers
given that the block layer already merges segments higher up.
prev parent reply other threads:[~2018-03-29 18:15 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-29 16:07 [PATCH 0/4] SGL alloc and free helper functions for requests Logan Gunthorpe
2018-03-29 16:07 ` [PATCH 1/4] nvmet: Introduce helper functions to allocate and free request SGLs Logan Gunthorpe
2018-03-29 16:07 ` [PATCH 2/4] nvmet-rdma: Use new SGL alloc/free helper for requests Logan Gunthorpe
2018-04-04 12:43 ` Sagi Grimberg
2018-04-04 16:47 ` Logan Gunthorpe
2018-03-29 16:07 ` [PATCH 3/4] nvmet-fc: Don't use the count returned by the dma_map_sg call Logan Gunthorpe
2018-03-29 16:14 ` Bart Van Assche
2018-03-29 16:15 ` Logan Gunthorpe
2018-03-29 16:38 ` Logan Gunthorpe
2018-03-29 16:24 ` James Smart
2018-03-29 16:30 ` Logan Gunthorpe
2018-03-29 16:34 ` James Smart
2018-04-04 12:45 ` Sagi Grimberg
2018-03-29 16:07 ` [PATCH 4/4] nvmet-fc: Use new SGL alloc/free helper for requests Logan Gunthorpe
2018-03-29 16:52 ` James Smart
2018-03-29 17:02 ` Logan Gunthorpe
2018-03-29 17:39 ` James Smart
2018-03-29 18:15 ` Christoph Hellwig [this message]
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