Re: Fwd: Ext4 bug with fallocate

[Eric Sandeen <sandeen@redhat.com>]

Fredrik Andersson wrote:
> Hi, I'd like to report what I'm fairly certain is an ext4 bug. I hope
> this is the right place to do so.
> 
> My program creates a big file (around 30 GB) with posix_fallocate (to
> utilize extents), fills it with data and uses ftruncate to crop it to
> its final size (usually somewhere between 20 and 25 GB).
> The problem is that in around 5% of the cases, the program locks up
> completely in a syscall. The process can thus not be killed even with
> kill -9, and a reboot is all that will do.


Not trying to ignore you, but trying to sort out some corruption issues 
that I'm afraid I have to rank higher than a hang for now...

 From the traces, things are hung up on the i_data_sem; several 
pdflushes want it for read in ext4_get_blocks_wrap, and drbdmakes 
presumably have it downed for write in ext4_ext_truncate.  I'm not 
immediately seeing the deadlock tonight, but then it's getting late...

Is the application that's triggering this something you can share?

Thanks,
-Eric