From: Jason Gunthorpe <jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
To: Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
Cc: linux-nvdimm-y27Ovi1pjclAfugRpC6u6w@public.gmane.org,
dri-devel-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org,
dm-devel-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org,
target-devel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
Sumit Semwal
<sumit.semwal-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>,
devel-gWbeCf7V1WCQmaza687I9mD2FQJk+8+b@public.gmane.org,
"James E.J. Bottomley"
<jejb-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>,
linux-scsi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
Matthew Wilcox <mawilcox-0li6OtcxBFHby3iVrkZq2A@public.gmane.org>,
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Jens Axboe <axboe-tSWWG44O7X1aa/9Udqfwiw@public.gmane.org>,
"Martin K. Petersen"
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Subject: Re: [PATCH v2 01/21] scatterlist: Introduce sg_map helper functions
Date: Thu, 27 Apr 2017 09:27:20 -0600 [thread overview]
Message-ID: <20170427152720.GA7662@obsidianresearch.com> (raw)
In-Reply-To: <20170427065338.GA20677-jcswGhMUV9g@public.gmane.org>
On Thu, Apr 27, 2017 at 08:53:38AM +0200, Christoph Hellwig wrote:
> > The main difficulty we
> > have now is that neither of those functions are expected to fail and we
> > need them to be able to in cases where the page doesn't map to system
> > RAM. This patch series is trying to address it for users of scatterlist.
> > I'm certainly open to other suggestions.
>
> I think you'll need to follow the existing kmap semantics and never
> fail the iomem version either. Otherwise you'll have a special case
> that's almost never used that has a different error path.
How about first switching as many call sites as possible to use
sg_copy_X_buffer instead of kmap?
A random audit of Logan's series suggests this is actually a fairly
common thing.
eg drivers/mmc/host/sdhci.c is only doing this:
buffer = sdhci_kmap_atomic(sg, &flags);
memcpy(buffer, align, size);
sdhci_kunmap_atomic(buffer, &flags);
drivers/scsi/mvsas/mv_sas.c is this:
+ to = sg_map(sg_resp, 0, SG_KMAP_ATOMIC);
+ memcpy(to,
+ slot->response + sizeof(struct mvs_err_info),
+ sg_dma_len(sg_resp));
+ sg_unmap(sg_resp, to, 0, SG_KMAP_ATOMIC);
etc.
Lots of other places seem similar, if not sometimes a little bit more
convoluted..
Switching all the trivial cases to use copy might bring more clarity
as to what is actually required for the remaining few users? If there
are only a few then it may no longer matter if the API is not idyllic.
Jason
WARNING: multiple messages have this Message-ID (diff)
From: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Logan Gunthorpe <logang@deltatee.com>,
linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org,
linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org,
intel-gfx@lists.freedesktop.org, linux-raid@vger.kernel.org,
linux-mmc@vger.kernel.org, linux-nvdimm@ml01.01.org,
linux-scsi@vger.kernel.org, open-iscsi@googlegroups.com,
megaraidlinux.pdl@broadcom.com, sparmaintainer@unisys.com,
devel@driverdev.osuosl.org, target-devel@vger.kernel.org,
netdev@vger.kernel.org, linux-rdma@vger.kernel.org,
dm-devel@redhat.com,
"Martin K. Petersen" <martin.petersen@oracle.com>,
"James E.J. Bottomley" <jejb@linux.vnet.ibm.com>,
Jens Axboe <axboe@kernel.dk>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Dan Williams <dan.j.williams@intel.com>,
Ross Zwisler <ross.zwisler@linux.intel.com>,
Matthew Wilcox <mawilcox@microsoft.com>,
Sumit Semwal <sumit.semwal@linaro.org>,
Stephen Bates <sbates@raithlin.com>
Subject: Re: [PATCH v2 01/21] scatterlist: Introduce sg_map helper functions
Date: Thu, 27 Apr 2017 09:27:20 -0600 [thread overview]
Message-ID: <20170427152720.GA7662@obsidianresearch.com> (raw)
In-Reply-To: <20170427065338.GA20677@lst.de>
On Thu, Apr 27, 2017 at 08:53:38AM +0200, Christoph Hellwig wrote:
> > The main difficulty we
> > have now is that neither of those functions are expected to fail and we
> > need them to be able to in cases where the page doesn't map to system
> > RAM. This patch series is trying to address it for users of scatterlist.
> > I'm certainly open to other suggestions.
>
> I think you'll need to follow the existing kmap semantics and never
> fail the iomem version either. Otherwise you'll have a special case
> that's almost never used that has a different error path.
How about first switching as many call sites as possible to use
sg_copy_X_buffer instead of kmap?
A random audit of Logan's series suggests this is actually a fairly
common thing.
eg drivers/mmc/host/sdhci.c is only doing this:
buffer = sdhci_kmap_atomic(sg, &flags);
memcpy(buffer, align, size);
sdhci_kunmap_atomic(buffer, &flags);
drivers/scsi/mvsas/mv_sas.c is this:
+ to = sg_map(sg_resp, 0, SG_KMAP_ATOMIC);
+ memcpy(to,
+ slot->response + sizeof(struct mvs_err_info),
+ sg_dma_len(sg_resp));
+ sg_unmap(sg_resp, to, 0, SG_KMAP_ATOMIC);
etc.
Lots of other places seem similar, if not sometimes a little bit more
convoluted..
Switching all the trivial cases to use copy might bring more clarity
as to what is actually required for the remaining few users? If there
are only a few then it may no longer matter if the API is not idyllic.
Jason
next prev parent reply other threads:[~2017-04-27 15:27 UTC|newest]
Thread overview: 183+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-25 18:20 [PATCH v2 00/21] Introduce common scatterlist map function Logan Gunthorpe
2017-04-25 18:20 ` Logan Gunthorpe
2017-04-25 18:20 ` Logan Gunthorpe
2017-04-25 18:20 ` Logan Gunthorpe
2017-04-25 18:20 ` [PATCH v2 01/21] scatterlist: Introduce sg_map helper functions Logan Gunthorpe
2017-04-25 18:20 ` Logan Gunthorpe
2017-04-25 18:20 ` Logan Gunthorpe
2017-04-25 18:20 ` Logan Gunthorpe
2017-04-26 7:44 ` Christoph Hellwig
2017-04-26 7:44 ` Christoph Hellwig
2017-04-26 7:44 ` Christoph Hellwig
2017-04-26 7:44 ` Christoph Hellwig
2017-04-26 7:44 ` Christoph Hellwig
2017-04-26 18:11 ` Logan Gunthorpe
2017-04-26 18:11 ` Logan Gunthorpe
2017-04-26 18:11 ` Logan Gunthorpe
2017-04-26 18:11 ` Logan Gunthorpe
2017-04-27 6:53 ` Christoph Hellwig
2017-04-27 6:53 ` Christoph Hellwig
2017-04-27 6:53 ` Christoph Hellwig
2017-04-27 6:53 ` Christoph Hellwig
2017-04-27 6:53 ` Christoph Hellwig
[not found] ` <20170427065338.GA20677-jcswGhMUV9g@public.gmane.org>
2017-04-27 15:27 ` Jason Gunthorpe [this message]
2017-04-27 15:27 ` Jason Gunthorpe
[not found] ` <20170427152720.GA7662-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
2017-04-27 15:57 ` Logan Gunthorpe
2017-04-27 15:57 ` Logan Gunthorpe
2017-04-27 15:44 ` Logan Gunthorpe
2017-04-27 15:44 ` Logan Gunthorpe
2017-04-27 15:44 ` Logan Gunthorpe
2017-04-27 15:44 ` Logan Gunthorpe
2017-04-27 20:13 ` Logan Gunthorpe
2017-04-27 20:13 ` Logan Gunthorpe
2017-04-27 20:13 ` Logan Gunthorpe
2017-04-27 20:13 ` Logan Gunthorpe
2017-04-26 8:59 ` Christian König
2017-04-26 8:59 ` Christian König
2017-04-26 8:59 ` Christian König
2017-04-26 8:59 ` Christian König
2017-04-26 8:59 ` Christian König
2017-04-26 23:30 ` Logan Gunthorpe
2017-04-26 23:30 ` Logan Gunthorpe
2017-04-26 23:30 ` Logan Gunthorpe
2017-04-26 23:30 ` Logan Gunthorpe
2017-04-25 18:20 ` [PATCH v2 02/21] libiscsi: Add an internal error code Logan Gunthorpe
2017-04-25 18:20 ` Logan Gunthorpe
2017-04-25 18:20 ` Logan Gunthorpe
2017-04-25 18:20 ` Logan Gunthorpe
2017-04-26 7:48 ` Christoph Hellwig
2017-04-26 7:48 ` Christoph Hellwig
2017-04-26 7:48 ` Christoph Hellwig
2017-04-26 7:48 ` Christoph Hellwig
2017-04-26 7:48 ` Christoph Hellwig
2017-04-25 18:20 ` [PATCH v2 03/21] libiscsi: Make use of new the sg_map helper function Logan Gunthorpe
2017-04-25 18:20 ` Logan Gunthorpe
2017-04-25 18:20 ` Logan Gunthorpe
2017-04-25 18:20 ` Logan Gunthorpe
2017-04-25 18:20 ` [PATCH v2 04/21] target: Make use of the new sg_map function at 16 call sites Logan Gunthorpe
2017-04-25 18:20 ` Logan Gunthorpe
2017-04-25 18:20 ` Logan Gunthorpe
2017-04-25 18:20 ` Logan Gunthorpe
2017-04-25 18:20 ` [PATCH v2 05/21] drm/i915: Make use of the new sg_map helper function Logan Gunthorpe
2017-04-25 18:20 ` Logan Gunthorpe
2017-04-25 18:20 ` Logan Gunthorpe
2017-04-25 18:20 ` Logan Gunthorpe
2017-04-25 18:20 ` [PATCH v2 06/21] crypto: hifn_795x: " Logan Gunthorpe
2017-04-25 18:20 ` Logan Gunthorpe
2017-04-25 18:20 ` Logan Gunthorpe
2017-04-25 18:20 ` Logan Gunthorpe
2017-04-25 18:20 ` [PATCH v2 07/21] crypto: shash, caam: " Logan Gunthorpe
2017-04-25 18:20 ` Logan Gunthorpe
2017-04-25 18:20 ` Logan Gunthorpe
2017-04-25 18:20 ` Logan Gunthorpe
2017-04-27 3:56 ` Herbert Xu
2017-04-27 3:56 ` Herbert Xu
2017-04-27 3:56 ` Herbert Xu
2017-04-27 3:56 ` Herbert Xu
2017-04-27 3:56 ` Herbert Xu
2017-04-27 15:45 ` Logan Gunthorpe
2017-04-27 15:45 ` Logan Gunthorpe
2017-04-27 15:45 ` Logan Gunthorpe
2017-04-27 15:45 ` Logan Gunthorpe
2017-04-28 6:30 ` Herbert Xu
2017-04-28 6:30 ` Herbert Xu
2017-04-28 6:30 ` Herbert Xu
2017-04-28 6:30 ` Herbert Xu
2017-04-28 16:53 ` Logan Gunthorpe
2017-04-28 16:53 ` Logan Gunthorpe
2017-04-28 16:53 ` Logan Gunthorpe
2017-04-28 16:53 ` Logan Gunthorpe
2017-04-28 17:51 ` Herbert Xu
2017-04-28 17:51 ` Herbert Xu
2017-04-28 17:51 ` Herbert Xu
2017-04-28 17:51 ` Herbert Xu
2017-04-28 19:01 ` Logan Gunthorpe
2017-04-28 19:01 ` Logan Gunthorpe
2017-04-28 19:01 ` Logan Gunthorpe
2017-04-28 19:01 ` Logan Gunthorpe
2017-04-28 19:01 ` Logan Gunthorpe
2017-04-25 18:20 ` [PATCH v2 08/21] dm-crypt: Make use of the new sg_map helper in 4 call sites Logan Gunthorpe
2017-04-25 18:20 ` Logan Gunthorpe
2017-04-25 18:20 ` Logan Gunthorpe
2017-04-25 18:20 ` Logan Gunthorpe
2017-04-25 18:20 ` [PATCH v2 09/21] staging: unisys: visorbus: Make use of the new sg_map helper function Logan Gunthorpe
2017-04-25 18:20 ` Logan Gunthorpe
2017-04-25 18:20 ` Logan Gunthorpe
2017-04-25 18:20 ` Logan Gunthorpe
2017-04-25 18:20 ` [PATCH v2 10/21] RDS: " Logan Gunthorpe
2017-04-25 18:20 ` Logan Gunthorpe
2017-04-25 18:20 ` Logan Gunthorpe
2017-04-25 18:20 ` Logan Gunthorpe
2017-04-25 18:20 ` [PATCH v2 11/21] scsi: ipr, pmcraid, isci: Make use of the new sg_map helper Logan Gunthorpe
2017-04-25 18:20 ` Logan Gunthorpe
2017-04-25 18:20 ` Logan Gunthorpe
2017-04-25 18:20 ` Logan Gunthorpe
2017-04-25 18:20 ` [PATCH v2 12/21] scsi: hisi_sas, mvsas, gdth: Make use of the new sg_map helper function Logan Gunthorpe
2017-04-25 18:20 ` Logan Gunthorpe
2017-04-25 18:20 ` Logan Gunthorpe
2017-04-25 18:20 ` Logan Gunthorpe
2017-04-25 18:21 ` [PATCH v2 13/21] scsi: arcmsr, ips, megaraid: " Logan Gunthorpe
2017-04-25 18:21 ` Logan Gunthorpe
2017-04-25 18:21 ` Logan Gunthorpe
2017-04-25 18:21 ` Logan Gunthorpe
2017-04-25 18:21 ` [PATCH v2 14/21] scsi: libfc, csiostor: Change to sg_copy_buffer in two drivers Logan Gunthorpe
2017-04-25 18:21 ` Logan Gunthorpe
2017-04-25 18:21 ` Logan Gunthorpe
2017-04-25 18:21 ` Logan Gunthorpe
2017-04-25 18:21 ` [PATCH v2 15/21] xen-blkfront: Make use of the new sg_map helper function Logan Gunthorpe
2017-04-25 18:21 ` Logan Gunthorpe
2017-04-25 18:21 ` Logan Gunthorpe
2017-04-25 18:21 ` Logan Gunthorpe
2017-04-26 7:37 ` Roger Pau Monné
2017-04-26 7:37 ` Roger Pau Monné
2017-04-26 7:37 ` Roger Pau Monné
2017-04-26 7:37 ` Roger Pau Monné
2017-04-26 7:37 ` Roger Pau Monné
2017-04-27 20:19 ` Logan Gunthorpe
2017-04-27 20:19 ` Logan Gunthorpe
2017-04-27 20:19 ` Logan Gunthorpe
2017-04-27 20:19 ` Logan Gunthorpe
2017-04-27 20:19 ` Logan Gunthorpe
[not found] ` <df6586e2-7d45-6b0b-facb-4dea882df06e-OTvnGxWRz7hWk0Htik3J/w@public.gmane.org>
2017-04-27 20:53 ` Jason Gunthorpe
2017-04-27 20:53 ` Jason Gunthorpe
2017-04-27 20:53 ` Jason Gunthorpe
[not found] ` <20170427205339.GB26330-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
2017-04-27 21:53 ` Logan Gunthorpe
2017-04-27 21:53 ` Logan Gunthorpe
2017-04-27 21:53 ` Logan Gunthorpe
[not found] ` <02ba3c7b-5fab-a06c-fbbf-c3be1c0fae1b-OTvnGxWRz7hWk0Htik3J/w@public.gmane.org>
2017-04-27 22:11 ` Jason Gunthorpe
2017-04-27 22:11 ` Jason Gunthorpe
2017-04-27 22:11 ` Jason Gunthorpe
[not found] ` <20170427221132.GA30036-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
2017-04-27 23:03 ` Logan Gunthorpe
2017-04-27 23:03 ` Logan Gunthorpe
2017-04-27 23:03 ` Logan Gunthorpe
[not found] ` <3a7c0d27-0744-4e91-b37f-3885c50455e8-OTvnGxWRz7hWk0Htik3J/w@public.gmane.org>
2017-04-27 23:20 ` Jason Gunthorpe
2017-04-27 23:20 ` Jason Gunthorpe
2017-04-27 23:20 ` Jason Gunthorpe
2017-04-27 23:29 ` Logan Gunthorpe
2017-04-27 23:29 ` Logan Gunthorpe
2017-04-27 23:29 ` Logan Gunthorpe
2017-04-25 18:21 ` [PATCH v2 16/21] mmc: sdhci: " Logan Gunthorpe
2017-04-25 18:21 ` Logan Gunthorpe
2017-04-25 18:21 ` Logan Gunthorpe
2017-04-25 18:21 ` Logan Gunthorpe
2017-04-25 18:21 ` [PATCH v2 17/21] mmc: spi: " Logan Gunthorpe
2017-04-25 18:21 ` Logan Gunthorpe
2017-04-25 18:21 ` Logan Gunthorpe
2017-04-25 18:21 ` Logan Gunthorpe
2017-04-25 18:21 ` [PATCH v2 18/21] mmc: tmio: " Logan Gunthorpe
2017-04-25 18:21 ` Logan Gunthorpe
2017-04-25 18:21 ` Logan Gunthorpe
2017-04-25 18:21 ` Logan Gunthorpe
2017-04-25 18:21 ` [PATCH v2 19/21] mmc: sdricoh_cs: " Logan Gunthorpe
2017-04-25 18:21 ` Logan Gunthorpe
2017-04-25 18:21 ` Logan Gunthorpe
2017-04-25 18:21 ` Logan Gunthorpe
2017-04-25 18:21 ` [PATCH v2 20/21] mmc: tifm_sd: " Logan Gunthorpe
2017-04-25 18:21 ` Logan Gunthorpe
2017-04-25 18:21 ` Logan Gunthorpe
2017-04-25 18:21 ` Logan Gunthorpe
2017-04-25 18:21 ` [PATCH v2 21/21] memstick: " Logan Gunthorpe
2017-04-25 18:21 ` Logan Gunthorpe
2017-04-25 18:21 ` Logan Gunthorpe
2017-04-25 18:21 ` Logan Gunthorpe
2017-04-25 18:40 ` ✓ Fi.CI.BAT: success for Introduce common scatterlist map function (rev2) Patchwork
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