Need information regarding RAID 6 Async APIs for kernel version 2.6.27

Need information regarding RAID 6 Async APIs for kernel version 2.6.27

[Koti]

Hi All,

When I am using the linux kernel version 2.6.21, I applied the RAID5 and RAID6 
Async_tx APIs, and those are working fine.

But When I upgraded to linux kernel version 2.6.27, it has RAID5 async_tx APIs 
inline, but not the RAID6.

I downloaded the recent RAID6 async_tx APIs released on March2009, from the 
links

git://git.kernel.org/pub/scm/linux/kernel/git/djbw/async_tx.git raid6

git://git.kernel.org/pub/scm/linux/kernel/git/djbw/md.git raid6-for-neil


The following is my questions:
1) Is these are suitable for my kernel version, if not can you please provide 
me the link where I can get the patches for this kernel.

1) If these are currect one Iam looking, then I have a few more doubts while 
traversing the code, It has async calls like async_pq, async_r6_dd_recov, ...
From where these functions are invoked
how the link happens between these async calls and the md-raid driver.

Can anybody help in solving this problem, it is very useful for my work.
Thanks in advance for your support.


Thanks,
Satha Koti

Re: Need information regarding RAID 6 Async APIs for kernel version 2.6.27

[Dan Williams]

On Thu, May 28, 2009 at 10:57 AM, Koti <satha_koti@yahoo.co.in> wrote:
> Hi All,
>
> When I am using the linux kernel version 2.6.21, I applied the RAID5 and RAID6
> Async_tx APIs, and those are working fine.
>
> But When I upgraded to linux kernel version 2.6.27, it has RAID5 async_tx APIs
> inline, but not the RAID6.
>
> I downloaded the recent RAID6 async_tx APIs released on March2009, from the
> links
>
> git://git.kernel.org/pub/scm/linux/kernel/git/djbw/async_tx.git raid6
>
> git://git.kernel.org/pub/scm/linux/kernel/git/djbw/md.git raid6-for-neil
>
>
> The following is my questions:
> 1) Is these are suitable for my kernel version, if not can you please provide
> me the link where I can get the patches for this kernel.

The most up to date code is found in:
git://git.kernel.org/pub/scm/linux/kernel/git/djbw/async_tx.git raid6

It is based on the 2.6.29 kernel plus the patches that were merged for
drivers/md/ during the 2.6.30 merge window.  There is currently no
plan to provide updated patches for kernel versions prior to 2.6.29.

> 1) If these are currect one Iam looking, then I have a few more doubts while
> traversing the code, It has async calls like async_pq, async_r6_dd_recov, ...
> From where these functions are invoked
> how the link happens between these async calls and the md-raid driver.
>
> Can anybody help in solving this problem, it is very useful for my work.
> Thanks in advance for your support.

Please try the latest code in the raid6 branch, it has been updated
according to review comments and includes the changes to
drivers/md/raid5.c to invoke asynchronous raid6 operation.  Note that
this branch of the tree will periodically rebase as review feedback is
incorporated into the patches.  I understand this makes the tree
difficult to track with git.  My recommendation is to add it as a
remote branch and use git fetch and git reset to stay up to date:

git remote add async_tx
git://git.kernel.org/pub/scm/linux/kernel/git/djbw/async_tx.git
git fetch async_tx
git checkout -b test-raid6 async_tx/raid6

...then to update (assuming you are still on the test-raid6 branch):
git fetch async_tx
git reset async_tx/raid6

Regards,
Dan

Re: Need information regarding RAID 6 Async APIs for kernel version 2.6.27

[Dan Williams]

satha kottidi wrote:
> Hi all,
> 
> Dan thanks for your recommendations, I followed it, got the present 
> running branch and working on it.
> 
> I have one more rquest, presently I want to run the Async_tx APIs 
> (RAID6) in kernel 2.6.27, Is any suggestions for further process.
> 
> Is the only way I have to extract the changes in the branch and applied 
> to my kernel, or any other ways.
> 
> Can you please help me in this regard also.

Backporting is a black art, and is rarely straightforward.  In a perfect 
world you could use Stacked GIT to rebase all the relevant changes onto 
a 2.6.27 base with a script like:

git log --reverse v2.6.27..async_tx/raid6 --no-merges\
--pretty=format:"%H" drivers/md/md.c drivers/md/raid5.c drivers/dma/ \
crypto/async_tx/ > commits

git checkout -b 2.6.27-raid6 v2.6.27
stg init
cat commits | while read commit;
do
	stg pick $commit
done

...but there is a high likelihood to encounter merge conflicts and other 
  cross-tree dependencies especially when trying to backport across ~3 
kernel versions.

Good luck,
Dan