linux-kernel - Re: [PATCH] ext4: allow DAX writeback for hole punch

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Message-ID: <20160817180722.GB16779@linux.intel.com>
Date:	Wed, 17 Aug 2016 12:07:22 -0600
From:	Ross Zwisler <ross.zwisler@...ux.intel.com>
To:	Jan Kara <jack@...e.cz>
Cc:	Ross Zwisler <ross.zwisler@...ux.intel.com>,
	linux-kernel@...r.kernel.org, Theodore Ts'o <tytso@....edu>,
	Andreas Dilger <adilger.kernel@...ger.ca>,
	Dan Williams <dan.j.williams@...el.com>,
	Jan Kara <jack@...e.com>, linux-ext4@...r.kernel.org,
	linux-nvdimm@...ts.01.org
Subject: Re: [PATCH] ext4: allow DAX writeback for hole punch

On Wed, Aug 17, 2016 at 07:19:55PM +0200, Jan Kara wrote:
> On Wed 17-08-16 10:11:02, Ross Zwisler wrote:
> > Currently when doing a DAX hole punch with ext4 we fail to do a writeback.
> > This is because the logic around filemap_write_and_wait_range() in
> > ext4_punch_hole() only looks for dirty page cache pages in the radix tree,
> > not for dirty DAX exceptional entries.
> > 
> > Signed-off-by: Ross Zwisler <ross.zwisler@...ux.intel.com>
> 
> Thanks. The patch looks correct, you can add:
> 
> Reviewed-by: Jan Kara <jack@...e.cz>
> 
> Although why don't we just simplify the test below to
> mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)? After all the mapping should
> not have the dirty tag set if there are no pages / no entries?

Sure, that works.  I'll update to that in V2, and I'll add stable.  Thanks!