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Date: Thu, 30 Apr 2009 12:10:43 -0700
From: "Nicholas A. Bellinger" <nab@...ux-iscsi.org>
To: Boaz Harrosh <bharrosh@...asas.com>
Cc: linux-scsi <linux-scsi@...r.kernel.org>,
LKML <linux-kernel@...r.kernel.org>, Tejun Heo <tj@...nel.org>,
James Bottomley <James.Bottomley@...senPartnership.com>,
Hannes Reinecke <hare@...e.de>,
FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>,
Mike Christie <michaelc@...wisc.edu>,
Douglas Gilbert <dgilbert@...erlog.com>,
Christoph Hellwig <hch@....de>,
Jens Axboe <jens.axboe@...cle.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Vladislav Bolkhovitin <vst@...b.net>
Subject: Re: [PATCH] [Target_Core_Mod/pSCSI]: Add
block/blk-map.c:blk_rq_map_kern_sg() usage
On Thu, 2009-04-30 at 12:37 +0300, Boaz Harrosh wrote:
> On 04/29/2009 03:43 AM, Nicholas A. Bellinger wrote:
> > Greetings all,
> >
> > This patch adds a new version of pscsi_map_task_SG() for the Linux/SCSI
> > passthrough subsystem plugin for target_core_mod v3.0 that uses Tejun's blk-map
> > patches on v2.6.30-rcX from git.kernel.org/pub/scm/linux/kernel/tj/misc.git blk-map.
> > This patch adds a LINUX_USE_NEW_BLK_MAP define to allow both blk_rq_map_kern_sg() and
> > legacy, non blk_rq_map_kern_sg() operation (with some limitiations with the latter) to
> > function.
> >
> > Once Tejun's patches for block/blk-map.c:blk_rq_map_kern_sg() have been included
> > upstream, the legacy pscsi_map_task_SG() will be removed and blk-map will become
> > the preferred method for accessing struct scatterlist -> struct scsi_device for
> > SCSI target operations. For now, I have created a blk-map branch in lio-core-2.6.git with
> > LINUX_USE_NEW_BLK_MAP=1 and left LINUX_USE_NEW_BLK_MAP=0 in branch master.
> >
> > This patch also updates pscsi_map_task_non_SG()'s usage of blk_rq_map_kern(), whos
> > parameters have also been simplified in Tejun's patches. It has been tested with
> > lio-core-2.6.git branch master and blk-map and tested on v2.6.30-rc3 x86 32-bit
> > HVM. The lio-core-2.6.git tree can be found at:
> >
> > http://git.kernel.org/?p=linux/kernel/git/nab/lio-core-2.6.git;a=summary
> >
> > So far, using Tejun's new code with LINUX_USE_NEW_BLK_MAP=1 is passing badblocks from
> > target_core_Mod/pSCSI exported Vmware mpt-fusion virtual SCSI HBA of TYPE_DISK. Both the
> > ConfigFS 'file-descriptor' method and 'SCSI HCTL reference' method for accessing
> > struct scsi_device have been tested and are working with lio-core-2.6.git blk-map.
> >
> > Currently *without* the blk-map patches on v2.6.30-rc3, is target_core_mod/pSCSI export is
> > limited to TYPE_DISK and TYPE_ROM that reference a struct block_device using the ConfigFS
> > 'file descriptor' method. This is because bio_add_page() expects struct block_device to be
>
> Better use bio_add_pc_page(). bio_add_page is only meant for fs requests.
>
<nod>, I was only using bio_add_page() in the pre v2.6.30 code for
target_core_mod/pSCSI because bio_add_pc_page() is not exported from
fs/bio.c. Perhaps since bio_add_pc_page() is intended to be for SCSI
target mode with struct request it should be EXPORT_SYMBOL_GPL()..?
> > each struct bio associated with the struct request w/o Tejun's blk_rq_map_kern_sg().
> >
> > Thanks Tejun for this patch series! Things have been stable so far and I hope to try some
> > 'bare-metal' and IOV enabled Linux/SCSI target exports using this patch series, along with validating
> > blk-map on some non TYPE_DISK exports using target_core_mod/pSCSI. I believe you intend this series for
> > v2.6.31 correct..?
> >
> > Boaz, have you had a chance to port your stuff over to this yet..? Other comments..?
> >
>
> No. As I said, these patches were not good for me. I do not have scatterlist at all.
> I have a pre-made bio, both from filesystem and a block device. So my needs are different.
Understood..
> Please note that the patches as last sent, were not good in my opinion, for regressing on
> some robustness and performance issues.
>
> There might be another solution for you, BTW. I'll be reposting a James Bottomley's
> patch in 1-2 days that makes blk_rq_map_kern() append the buffers it receives instead
> of only supporting a single call. So you can allocate the request and call blk_rq_map_kern()
> in a loop for-each-sg. The bad thing with this is that the biovec inside will be allocated
> multiple times, jumping from small pools to bigger ones.
Ok, I will plan on testing both methods (single call
blk_rq_map_kern_sg() vs. appending buffers with blk_rq_map_kern()) using
the pSCSI export on v2.6.30-rc3..
> If only there was a way to specify a pre-allocated bio-size.
Hrrmm, can you explain a bit more about what this would entail..? From
the SCSI target API side, mapping a contigious array of struct
scatterlist's from the caller into struct request (and struct bio) in
place of bvec would still make the most sense I think.
In the OSD case where you are already passing into pre-formatted bio's
it would be up to the caller to format and validate the your pages via
an internally allocated (or preallocated) array of scatterlists.
Anyways, I will think about it some more and see what can be found..
>
> Patch is attached for convenience
>
> > --nab
> >
> > Signed-off-by: Nicholas A. Bellinger <nab@...ux-iscsi.org>
> > ---
> > drivers/target/MCONFIG_TARGET | 1 +
> > drivers/target/Makefile | 4 ++-
> > drivers/target/target_core_pscsi.c | 49 ++++++++++++++++++++++++++++++++++-
> > 3 files changed, 51 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/target/MCONFIG_TARGET b/drivers/target/MCONFIG_TARGET
> > index 8023deb..96541c4 100644
> > --- a/drivers/target/MCONFIG_TARGET
> > +++ b/drivers/target/MCONFIG_TARGET
> > @@ -22,3 +22,4 @@ LINUX_FILEIO ?= 1
> > LINUX_VPD_PAGE_CHECK?=1
> >
> > LIO_TARGET_CONFIGFS?=1
> > +LINUX_USE_NEW_BLK_MAP?=0
> > diff --git a/drivers/target/Makefile b/drivers/target/Makefile
> > index 47fef07..a19490d 100644
> > --- a/drivers/target/Makefile
> > +++ b/drivers/target/Makefile
> > @@ -73,7 +73,9 @@ endif
> > ifeq ($(LINUX_SCSI_MEDIA_ROM), 1)
> > EXTRA_CFLAGS += -DLINUX_SCSI_MEDIA_ROM
> > endif
> > -
> > +ifeq ($(LINUX_USE_NEW_BLK_MAP), 1)
> > +EXTRA_CFLAGS += -DLINUX_USE_NEW_BLK_MAP
> > +endif
> > ifeq ($(DEBUG_DEV), 1)
> > EXTRA_CFLAGS += -DDEBUG_DEV
> > endif
> > diff --git a/drivers/target/target_core_pscsi.c b/drivers/target/target_core_pscsi.c
> > index 0962563..0edcb9a 100644
> > --- a/drivers/target/target_core_pscsi.c
> > +++ b/drivers/target/target_core_pscsi.c
> > @@ -518,7 +518,12 @@ se_device_t *pscsi_create_virtdevice(
> > " parameter\n");
> > return NULL;
> > }
> > -
> > +#ifndef LINUX_USE_NEW_BLK_MAP
> > + printk(KERN_ERR "Sorry, when running on >= v2.6.30 w/o blk-map branch"
> > + " you need to use the ConfigFS file descriptor method for"
> > + " accessing Linux/SCSI passthrough storage objects\n");
> > + return -EINVAL;
> > +#endif
> > spin_lock_irq(sh->host_lock);
> > list_for_each_entry(sd, &sh->__devices, siblings) {
> > if (!(pdv->pdv_channel_id == sd->channel) ||
> > @@ -1269,6 +1274,39 @@ static inline struct bio *pscsi_get_bio(pscsi_dev_virt_t *pdv, int sg_num)
> > #define DEBUG_PSCSI(x...)
> > #endif
> >
> > +#ifdef LINUX_USE_NEW_BLK_MAP
>
> As I understand, you have a full Linux tree, at the git above.
> The LINUX_USE_NEW_BLK_MAP define is not nice. And only causes more work
> for you.
>
> You leave master branch code based on current Kernel.
>
> Then at blk-map branch you apply the correct lio patches together with Tejun's
> at the proper places. After the fixture or change you are looking for. As if
> lio was in kernel and this is the proper propagation of patches.
>
> If you do this because of an out-of-tree compilation support, then here
> too, you keep two branches, easily rebase two chains of patches, and provide
> a tar-ball for the kernel in question. (git-web just does that for you
> automatically.)
>
> Because look, as long as you have LINUX_USE_NEW_BLK_MAP usage (in any branch)
> then the code is not acceptable into mainline, and is just an experiment.
>
Yeah, I was using LINUX_USE_NEW_BLK_MAP as a temporary measure so that I
could keep both branches in sync for now. I will kill it moving
forward.
Thanks for your comments,
--nab
> > +
> > +/* pscsi_map_task_SG()
> > + *
> > + * This function uses the new struct scatterlist-> struct request mapping
> > + * from git.kernel.org/pub/scm/linux/kernel/tj/misc.git blk-map
> > + *
> > + * This code is not upstream yet, so lio-core-2.6.git now has a blk-map
> > + * branch until this happens..
> > + */
> > +int pscsi_map_task_SG(se_task_t *task)
> > +{
> > + pscsi_plugin_task_t *pt = (pscsi_plugin_task_t *) task->transport_req;
> > + struct request *rq = pt->pscsi_req;
> > + int ret;
> > + /*
> > + * For SCF_SCSI_DATA_SG_IO_CDB, use block/blk-map.c:blk_rq_map_kern_sg()
> > + * for mapping struct scatterlist to struct request. Thanks Tejun!
> > + */
> > + ret = blk_rq_map_kern_sg(rq, task->task_sg, task->task_sg_num,
> > + GFP_KERNEL);
> > + if (ret != 0) {
> > + printk(KERN_ERR "blk_rq_map_kern_sg() failed for rq: %p"
> > + " task_sg: %p task_sg_num: %u\n",
> > + rq, task->task_sg, task->task_sg_num);
> > + return -1;
> > + }
> > +
> > + return task->task_sg_num;
> > +}
> > +
> > +#else
> > +
> > /* pscsi_map_task_SG():
> > *
> > *
> > @@ -1376,6 +1414,9 @@ fail:
> > return ret;
> > }
> >
> > +#endif /* LINUX_USE_NEW_BLK_MAP */
> > +
> > +
> > /* pscsi_map_task_non_SG():
> > *
> > *
> > @@ -1389,10 +1430,14 @@ int pscsi_map_task_non_SG(se_task_t *task)
> >
> > if (!task->task_size)
> > return 0;
> > -
> > +#ifdef LINUX_USE_NEW_BLK_MAP
>
> source code is not a version management system, Use git for that
>
> > + ret = blk_rq_map_kern(pt->pscsi_req, T_TASK(cmd)->t_task_buf,
> > + task->task_size, GFP_KERNEL);
> > +#else
> > ret = blk_rq_map_kern(pdv->pdv_sd->request_queue,
> > pt->pscsi_req, T_TASK(cmd)->t_task_buf,
> > task->task_size, GFP_KERNEL);
> > +#endif
> > if (ret < 0) {
> > printk(KERN_ERR "PSCSI: blk_rq_map_kern() failed: %d\n", ret);
> > return PYX_TRANSPORT_LOGICAL_UNIT_COMMUNICATION_FAILURE;
>
>
> Cheers
> Boaz
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