mm: silently skip readahead for DAX inodes
authorRoss Zwisler <ross.zwisler@linux.intel.com>
Thu, 25 Aug 2016 22:17:17 +0000 (15:17 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Sat, 27 Aug 2016 00:39:35 +0000 (17:39 -0700)
commit11bd969fdefea3ac0cb9791224f1e09784e21e58
tree0acb5b64edc970860174c068698448b94f3122c8
parentd0e5845561c238619de9f5b77e0d763f4c331ca5
mm: silently skip readahead for DAX inodes

For DAX inodes we need to be careful to never have page cache pages in
the mapping->page_tree.  This radix tree should be composed only of DAX
exceptional entries and zero pages.

ltp's readahead02 test was triggering a warning because we were trying
to insert a DAX exceptional entry but found that a page cache page had
already been inserted into the tree.  This page was being inserted into
the radix tree in response to a readahead(2) call.

Readahead doesn't make sense for DAX inodes, but we don't want it to
report a failure either.  Instead, we just return success and don't do
any work.

Link: http://lkml.kernel.org/r/20160824221429.21158-1-ross.zwisler@linux.intel.com
Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reported-by: Jeff Moyer <jmoyer@redhat.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Jan Kara <jack@suse.com>
Cc: <stable@vger.kernel.org> [4.5+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mm/readahead.c