Re: block allocator issue with ext4+DAX

From	Ross Zwisler <ross.zwisler@linux.intel.com>
Newsgroups	linux.kernel
Subject	Re: block allocator issue with ext4+DAX
Date	2016-03-31 17:20 +0200
Message-ID	<riMy6-71p-5@gated-at.bofh.it> (permalink)
References	<riwtk-3p2-1@gated-at.bofh.it> <riGCm-2kC-3@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Thu, Mar 31, 2016 at 10:59:25AM +0200, Jan Kara wrote:
> On Wed 30-03-16 16:01:29, Ross Zwisler wrote:
> > I've hit an issue in my testing which I believe to be related to the ext4
> > block allocator when using the DAX mount option.  I originally found this
> > issue with the generic/102 xfstest, but have reduced it to the minimal
> > reproducer at the bottom of this email.  I've been able to reproduce this with
> > both BRD and with PMEM as the underlying block device.
> > 
> > For this test we're running in a very small filesystem, only 512 MiB.  We
> > fallocate() 400 MiB of that space, unlink the file, then try and rewrite that
> > 400 MiB file one chunk at a time.
> > 
> > What actually happens is that during the rewrite we run out of memory and the
> > DAX call to get_block() in dax_io() fails with -ENOSPC.
> 
> Yes, I have already sent a fix for this bug here:
> 
> http://www.spinics.net/lists/linux-ext4/msg51649.html
> 
> Ted, can you please pick it up? Thanks!
> 
> 								Honza

Yay!

Ted, you can add my

Tested-by: Ross Zwisler <ross.zwisler@linux.intel.com>

to that patch.

Thanks for the fix, Jan!

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block allocator issue with ext4+DAX Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-03-31 00:10 +0200
  Re: block allocator issue with ext4+DAX Jan Kara <jack@suse.cz> - 2016-03-31 11:00 +0200
    Re: block allocator issue with ext4+DAX Ross Zwisler <ross.zwisler@linux.intel.com> - 2016-03-31 17:20 +0200

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