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SubjectRe: Rampant ext3/4 corruption on 2.6.34-rc7 with VIVT ARM (Marvell 88f5182)
On Tue, 2010-05-11 at 19:23 +1000, Benjamin Herrenschmidt wrote:

> Since I doubt ext3 is busted so dramatically in mainline for "normal" machines,
> I tend to suspect things could be related to the infamous vivt caches. On the
> other hand, it's pretty clearly metadata or journal corruption and I'm not
> sure we ever do things that could cause aliases (such as vmap etc..) on
> these things, and they shouldn't be mapped into userspace... unless it's fsck
> itself that causes aliases to occur at the block device level ? (I do unmount
> though before I run fsck).
> On the other hand, it could also be a busticated marvell SATA driver :-)
> I have no problem with the vendor kernel, but it's ancient (2.6.12) and based
> on an out of tree variant of a Marvell originated BSP, so everything is
> completely different, especially in the area of drivers for the chipset.
> Anyways, I'll see if I can gather more data tomorrow as time, viruses and sick
> kids permits.
> In the meantime, any hint appreciated.

A quick other test which brings more infos, using a smaller (about 5GB)
partition and no md or raid involved:

- Boot with NFS root
- mkfs /dev/sdb2 (no md or raid involved)
- mount /dev/sdb2 /mnt/test
- rsync -avx /test-stuff /mnt/test
- cd /mnt/test
- md5sum -c ~/test-stuff-sums.txt

That gives me a whole bunch of:

md5sum: ./usr/bin/debconf-escape: No such file or directory
./usr/bin/debconf-escape: FAILED open or read
./usr/bin/stat: OK
md5sum: ./usr/bin/chrt: No such file or directory
./usr/bin/chrt: FAILED open or read

In fact, if I do ls /mnt/test/usr/bin/ I see debconf but if I do
ls /mnt/test/usr/bin/chrt then I get No such file or directory.

So something is badly wrong :-)

Now, trying without the dir_index feature (mkfs.ext3 -O ^dir_index)
and it works fine. All my md5sum's are correct and fsck passes.

So there's what looks like a problem specific to htree's. I don't think
it's a SATA driver problem (doesn't smell like it but we can't
completely dismiss the possibility yet). Could be a VIVT issue but then
why ? I don't see ext3 playing with virtual mappings and none of that
should alias with userspace...

Or is it incorrectly accessing pages while they are DMA'ed to or from ?
IE. Accessing with the CPU pages between dma_map_* and dma_unmap_* ?
That will break on a number of setups including swiotlb on x86 so I tend
to doubt it but who knows...

Anyways, enough for tonight.


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