Re: 2.6.19 file content corruption on ext3

[Andrei Popa <andrei.popa@i-neo.ro>]

On Mon, 2006-12-18 at 17:21 -0800, Andrew Morton wrote:
> On Mon, 18 Dec 2006 16:57:30 -0800 (PST)
> Linus Torvalds <torvalds@osdl.org> wrote:
> 
> > What happens if you only ifdef out that single thing? 
> > 
> > The actual page-cleaning functions make sure to only clear the TAG_DIRTY 
> > bit _after_ the page has been marked for writeback. Is there some ordering 
> > constraint there, perhaps?
> > 
> > I'm really reaching here. I'm trying to see the pattern, and I'm not 
> > seeing it. I'm asking you to test things just to get more of a feel for 
> > what triggers the failure, than because I actually have any kind of idea 
> > of what the heck is going on.
> > 
> > Andrew, Nick, Hugh - any ideas?
> 
> If all of test_clear_page_dirty() has been commented out then the page will
> never become clean hence will never fall out of pagecache, so unless Andrei
> is doing a reboot before checking for corruption, perhaps the underlying
> data on-disk is incorrect, but we can't see it.

if I do a sync and echo 1 > /proc/sys/vm/drop_caches does the reboot is
still necesary ?

> 
> Andrei, how _are_ you running this test?    What's the exact sequence of steps?
> 
> In particular, are you doing anything which would cause the corrupted file
> to be evicted from memory, thus forcing a read from disk?  Such as
> unmounting and then remounting the filesystem?

I boot linux, I start rtorrent and start the download, while it's
downloading I start evolution and i check my mail(my mbox is very large,
several hundered megabytes), I close evolution(I use evolution just to
have another application witch uses the filesystem and the memory), I
start evolution again. I start firefox. The download is complete.
Rtorrent says if the hash is good or not. I do a "unrar t qwe.rar" to
test that all 84 downloaded rar files are ok and see the result.

> 
> The point of my question is to check that the data is really incorrect
> on-disk, or whether it is incorrect in pagecache.
> 
> Also, it'd be useful if you could determine whether the bug appears with
> the ext2 filesystem: do s/ext3/ext2/ in /etc/fstab, or boot with
> rootfstype=ext2 if it's the root filesystem.

I will test.

> 
> Thanks.

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