lkml.org 
[lkml]   [2016]   [Sep]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 4.7 110/143] mm: silently skip readahead for DAX inodes
Date
4.7-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ross Zwisler <ross.zwisler@linux.intel.com>

commit 11bd969fdefea3ac0cb9791224f1e09784e21e58 upstream.

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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
mm/readahead.c | 9 +++++++++
1 file changed, 9 insertions(+)

--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -8,6 +8,7 @@
*/

#include <linux/kernel.h>
+#include <linux/dax.h>
#include <linux/gfp.h>
#include <linux/export.h>
#include <linux/blkdev.h>
@@ -545,6 +546,14 @@ do_readahead(struct address_space *mappi
if (!mapping || !mapping->a_ops)
return -EINVAL;

+ /*
+ * 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.
+ */
+ if (dax_mapping(mapping))
+ return 0;
+
return force_page_cache_readahead(mapping, filp, index, nr);
}


\
 
 \ /
  Last update: 2016-09-17 09:58    [W:0.491 / U:0.020 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site