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Date: Thu, 24 Aug 2017 15:45:00 +0200
From: Christoph Hellwig <hch@lst.de>
To: Dan Williams <dan.j.williams@intel.com>
Cc: linux-nvdimm@lists.01.org, linux-fsdevel@vger.kernel.org
Subject: fs_dax_get_by_host in the hot path
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Hi Dan,

I just noticed that we now do a fs_dax_get_by_host in every
iomap_begin call for DAX.  This function iterates a list,
does a string compared and igrab.  I really think we need
to cache this in the superblock (possible even the fs
superblock) similar to what we do for the block device.