Re: [PATCH 1/2] block: fix leaks associated with discard requestpayload

From: FUJITA Tomonori
Date: Wed Jun 30 2010 - 07:56:26 EST

On Mon, 28 Jun 2010 17:25:36 +0200
Christoph Hellwig <hch@xxxxxx> wrote:

> On Mon, Jun 28, 2010 at 05:14:28PM +0900, FUJITA Tomonori wrote:
> > > While I see the problems with leaking ressources in that case I still
> > > can't quite explain the hang I see.
> >
> > Any way to reproduce the hang without ssd drives?
> Actually the SSDs don't fully hang, they just causes lots of I/O errors
> and hit the error handler hard. The hard hang is when running under
> qemu. Apply the patch below, then create an if=scsi drive that resides
> on an XFS filesystem, and you'll have scsi TP support in the guest:

Ok, I figured out what's wrong.

As I suspected, it's due to the partial completion.

qemu scsi driver tells that the WRITE_SAME command was successful but
somehow the command has resid. So we retry it again and again (and
leak some memory).

I don't know yet why qemu scsi driver is broken. Maybe there is a bug
in it or converting discard to FS sends broken commands to the driver.

I'll try to figure out it tomorrow.

I've put a patch to complete discard command in the all-or-nothing

git:// discard

At least, the guest kernel doesn't hang for me.
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