tree 52e8c6f6bea775cb623cfca46012b91657b7dc47
parent c6dcf52c23d2d3fb5235cec42d7dd3f786b87d55
author Jan Kara <jack@suse.cz> 1470841828 +0200
committer Dan Williams <dan.j.williams@intel.com> 1482812964 -0800

dax: Avoid page invalidation races and unnecessary radix tree traversals

Currently dax_iomap_rw() takes care of invalidating page tables and
evicting hole pages from the radix tree when write(2) to the file
happens. This invalidation is only necessary when there is some block
allocation resulting from write(2). Furthermore in current place the
invalidation is racy wrt page fault instantiating a hole page just after
we have invalidated it.

So perform the page invalidation inside dax_iomap_actor() where we can
do it only when really necessary and after blocks have been allocated so
nobody will be instantiating new hole pages anymore.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>