[PATCH 0/3] Add disk hotswap support to libata

[PATCH 0/3] Add disk hotswap support to libata

[Lukasz Kosewski]

Hey all, introductory blurb here.

This sequence of patches will add a framework to libata to allow for 
hot-swapping disks in and out.

There are three patches:
01-promise_sataII150_support
02-libata_hotswap_infrastructure
03-promise_hotswap_support

The rationale for each will be described in following emails.

I encourage anyone with design ideas to come forward and contribute, and 
anyone who can see concurrency problems (I will describe what I see as 
issues along with the second patch) to suggest fixes.

Thus far, I've tested this HEAVILY with a 2.6.11.12 kernel + 
2.6.11-libata-dev1.patch.  I have found no issues outstanding on that 
kernel.  All testing was done with Promise SATA150 and SATAII150 Tx4/Tx2 
  Plus controllers and a huge variety of Western Digital and Seagate disks.

I have ported my patches to 2.6.13-rc3 and 2.6.13-rc3-mm1, and have 
tested on the latter as well; they work identically to the 2.6.11 tests 
except for a breakage in the SCSI layer [1].

The patches I will attach apply to the latter (2.6.13-rc3-mm1) tree, 
since I expect that by the time people start looking at them seriously, 
the existing libata patches in that tree will have become part of 
mainline.  If this is NOT the right thing to do, please tell me, and 
I'll submit patches for the requested kernel version.

Enjoy!

Luke Kosewski
Human Cannonball
Net Integration Technologies

[1]  The SCSI error on 2.6.13-rc3-mm1 that I found:
'echo "scsi add-single-device a b c d" > /proc/scsi/scsi'  //works, or 
no-op if the sd corresponding to that device is there already
'echo "scsi remove-single-device a b c d" > /proc/scsi/scsi'  //works
'echo "scsi add-single-device a b c d" > /proc/scsi/scsi'  //works
'echo "scsi remove-single-device a b c d" > /proc/scsi/scsi'  //FAILS

As such, since the same underlying functions are called by hotplugging, 
you will only be able to remove a disk from a device once before it 
fails, until this error is fixed.  I'll look into it as well.

Re: [PATCH 0/3] Add disk hotswap support to libata

[Michael Tokarev]

Lukasz Kosewski wrote:
[]
> [1]  The SCSI error on 2.6.13-rc3-mm1 that I found:
> 'echo "scsi add-single-device a b c d" > /proc/scsi/scsi'  //works, or 
> no-op if the sd corresponding to that device is there already
> 'echo "scsi remove-single-device a b c d" > /proc/scsi/scsi'  //works
> 'echo "scsi add-single-device a b c d" > /proc/scsi/scsi'  //works
> 'echo "scsi remove-single-device a b c d" > /proc/scsi/scsi'  //FAILS

echo -n 1 > /sys/.../hostA/targetA:B:C/A:B:C:D/delete
still works.  I think.
And (again, I think) this same problem exists with 2.6.11 as well.
At least, I wasn't able to remove-single-device even once (I discovered
this mechanism only recently, haven't tried it with other kernels).

> As such, since the same underlying functions are called by hotplugging, 
> you will only be able to remove a disk from a device once before it 
> fails, until this error is fixed.  I'll look into it as well.

/mjt

Re: [PATCH 0/3] Add disk hotswap support to libata

[Lukasz Kosewski]

Michael Tokarev wrote:
> echo -n 1 > /sys/.../hostA/targetA:B:C/A:B:C:D/delete
> still works.  I think.
> And (again, I think) this same problem exists with 2.6.11 as well.
> At least, I wasn't able to remove-single-device even once (I discovered
> this mechanism only recently, haven't tried it with other kernels).

You're both correct and incorrect based on my testing; in 2.6.11.12, I 
have no problems.

However, in 2.6.13-rc1-mm1, you're right that echoing 1 into the delete 
node does remove the device.

It seems that there is some issue with the 'scsi_device_lookup' function 
then?

I'd have to debug further.

Luke Kosewski
Human Cannonball
Net Integration Technologies

Re: [PATCH 0/3] Add disk hotswap support to libata

[Jeff Garzik]

Lukasz Kosewski wrote:
> Hey all, introductory blurb here.
> 
> This sequence of patches will add a framework to libata to allow for 
> hot-swapping disks in and out.
> 
> There are three patches:
> 01-promise_sataII150_support
> 02-libata_hotswap_infrastructure
> 03-promise_hotswap_support

Pretty cool stuff!

As soon as I finish SATA ATAPI (this week[end]), I'll take a look at 
this.  A quick review of the patches didn't turn up anything terribly 
objectionable, though :)

	Jeff


P.S.  You might want to CC linux-ide as well, on libata patches.

Re: [PATCH 0/3] Add disk hotswap support to libata

[Lukasz Kosewski]

On 7/21/05, Jeff Garzik <jgarzik@pobox.com> wrote:
> 
> Pretty cool stuff!
> 
> As soon as I finish SATA ATAPI (this week[end]), I'll take a look at
> this.  A quick review of the patches didn't turn up anything terribly
> objectionable, though :)

Excellent!  Thanks for the quick turnaround!

> P.S.  You might want to CC linux-ide as well, on libata patches. 

I've CCed the original patches to Linux-ide for comments.  Also, I've
re-sent patch 3 with a minor fix to boolean logic with bits.

Enjoy!

Luke Kosewski
Human Cannonball
Net Integration Technologies

Re: [PATCH 0/3] Add disk hotswap support to libata

[Doug Maxey]

On Thu, 21 Jul 2005 21:35:24 EDT, Jeff Garzik wrote:
>As soon as I finish SATA ATAPI (this week[end]), I'll take a look at 
>this.  A quick review of the patches didn't turn up anything terribly 
>objectionable, though :)
>

I would like to offer to test when you are ready.  Some older and new SATAPI 
drives, various chipsets (ICH{5,6}, TX4 on the way).  And a SATA analyzer 
for anything really odd. 

++doug

Re: [PATCH 0/3] Add disk hotswap support to libata

[Jeff Garzik]

Doug Maxey wrote:
> On Thu, 21 Jul 2005 21:35:24 EDT, Jeff Garzik wrote:
> 
>>As soon as I finish SATA ATAPI (this week[end]), I'll take a look at 
>>this.  A quick review of the patches didn't turn up anything terribly 
>>objectionable, though :)
>>
> 
> 
> I would like to offer to test when you are ready.  Some older and new SATAPI 
> drives, various chipsets (ICH{5,6}, TX4 on the way).  And a SATA analyzer 
> for anything really odd. 

Great!

It'll be posted here on linux-ide, so just keep an eye out.

Analysis of any portion of libata, with a SATA analyzer, would be much 
appreciated.

	Jeff