Never mind my ranting.
The problem was in the extent disk format of ext4. I had forgot that
ext4 uses extents for all new files by default. Old grub won't read extents.
Oh, well... nothing like wasting hard working peoples time with stupid
things. Anyway. SWIOTLB for 32-bit PAE should be a good thing though. :)
Regards,
Christian
On 10/05/2015 01:35 PM, Christian Melki wrote:
Hi.
I think I rang the bell a bit early. The corruption is in grub legacy (I
assumed that would be in Linux too, but it wasn't). The on disk format
of ext4 apparently stores byte ordering somehow? I thought the on disk
format of ext4 was a specific endian (little). Since only that file is
unreadable in grub, but readable in Linux.. I am guessing endian issues
somehow.. which still is strange.
Regards,
Christian
On 10/03/2015 08:00 PM, Konrad Rzeszutek Wilk wrote:
On Sat, Oct 03, 2015 at 09:36:30AM -0500, Bjorn Helgaas wrote:
[+cc Konrad, Joerg, iommu list]
On Fri, Oct 02, 2015 at 04:20:16PM +0200, Christian Melki wrote:
I discovered a strange error on my machine. 32-bit PAE 4.2.0 without
IOMMU code (yeah, I know).
When writing to an ext4 filesystem on a USB disk my kernel would hang
and not return control to userspace. It would spew kernel messages to
syslog as fast as it could without giving userspace any time, ie "hang"
as far as a user sees it. The device itself is ok and the filesystem is
clean.
I get messages like this, millions of them.
Oct 2 14:33:06 voodoochild kernel: [ 223.287447] nommu_map_sg:
overflow 25dcac000+1024 of device mask ffffffff
Oct 2 14:33:06 voodoochild kernel: [ 223.287448] nommu_map_sg:
overflow 25dcac000+1024 of device mask ffffffff
Oct 2 14:33:06 voodoochild kernel: [ 223.287449] nommu_map_sg:
overflow 25dcac000+1024 of device mask ffffffff
I disovered that SWIOTLB was not on. It is only provided for 64-bit
machines where it is default. On 32-bit SWIOTLB seems disabled
unless you are running with some IOMMU/AGPGART code.
But what about 32-bit PAE? Would that not qualify for SWIOTLB
without IOMMU?
It most certainly would!
I am a novice in this area. Maybe this is a Kconfig "bug" for us
that like to hang ourselves with CONFIG_* rope? :) I'd like to think
that SWIOTLB should be default for 32-bit PAE too?
Aye. I presume that you had done a small change already for this?
Would you be willing to post it on lkml and CC me ?
Thank you.
Best regards,
Christian
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