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SubjectRe: [PATCH v2]: New implementation of scsi_execute_async()
Vladislav Bolkhovitin, on 07/14/2009 08:17 PM wrote:
> This patch reimplements scsi_execute_async(). In the new version it's a lot less
> hackish and also has additional features. Namely:
>
> 1. Possibility to insert commands both in tail and in head of the queue.
>
> 2. Possibility to explicitly specify if the last SG element has space for padding.
>
> This patch based on the previous patches posted by Tejun Heo. Comparing to them
> it has the following improvements:
>
> 1. It uses BIOs chaining instead of kmalloc()ing the whole bio.
>
> 2. It uses SGs chaining instead of kmalloc()ing one big SG in case if direct
> mapping failed (e.g. because of DMA alignment or padding).
>
> 3. If direct mapping failed, if possible, it copies only the last SG element,
> not the whole SG.
>
> 4. When needed, copy_page() is used instead of memcpy() to copy the whole pages.
>
> Also this patch adds and exports functions sg_copy() and sg_copy_elem(), which
> cop one SG to another and one SG element to another respectively.
>
> At the moment SCST is the only user of this functionality. It needs it, because
> its target drivers, which are, basically, SCSI drivers, can deal only with SGs,
> not with BIOs. But, according the latest discussions, there are other potential
> users for of this functionality, so I'm sending this patch in a hope that it will be
> also useful for them and eventually will be merged in the mainline kernel.
>
> This patch requires previously sent patch with subject "[PATCH]: Rename REQ_COPY_USER
> to more descriptive REQ_HAS_TAIL_SPACE_FOR_PADDING".
>
> It's against 2.6.30.1, but if necessary, I can update it to any necessary
> kernel version.
>
> Signed-off-by: Vladislav Bolkhovitin <vst@vlnb.net>
>
> block/blk-map.c | 408 ++++++++++++++++++++++++++++++++++++++++++++
> drivers/scsi/scsi_lib.c | 108 +++++++++++
> include/linux/blkdev.h | 3
> include/linux/scatterlist.h | 7
> include/scsi/scsi_device.h | 11 +
> lib/scatterlist.c | 147 +++++++++++++++
> 6 files changed, 683 insertions(+), 1 deletion(-)

Oops, sorry, forgot to write the change log from v1. V2 has fixes
according to comments made by Joe Eykholt and Boaz Harrosh.

Vlad



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