This is a note to let you know that I've just added the patch titled
mm: silently skip readahead for DAX inodes
to the 4.7-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
mm-silently-skip-readahead-for-dax-inodes.patch
and it can be found in the queue-4.7 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 11bd969fdefea3ac0cb9791224f1e09784e21e58 Mon Sep 17 00:00:00 2001
From: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
Date: Thu, 25 Aug 2016 15:17:17 -0700
Subject: mm: silently skip readahead for DAX inodes
From: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
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@xxxxxxxxxxxxxxx
Signed-off-by: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
Reported-by: Jeff Moyer <jmoyer@xxxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Dave Chinner <david@xxxxxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Jan Kara <jack@xxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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);
}
Patches currently in stable-queue which might be from ross.zwisler@xxxxxxxxxxxxxxx are
queue-4.7/libnvdimm-nd_blk-mask-off-reserved-status-bits.patch
queue-4.7/mm-silently-skip-readahead-for-dax-inodes.patch
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