3.10-stable patches

added patches:
	md-raid5-disable-discard-by-default-due-to-safety-concerns.patch

diff --git a/queue-3.10/md-raid5-disable-discard-by-default-due-to-safety-concerns.patch b/queue-3.10/md-raid5-disable-discard-by-default-due-to-safety-concerns.patch
new file mode 100644 (file)
index 0000000..3fd976f
--- /dev/null
+++ b/queue-3.10/md-raid5-disable-discard-by-default-due-to-safety-concerns.patch
@@ -0,0 +1,94 @@
+From 8e0e99ba64c7ba46133a7c8a3e3f7de01f23bd93 Mon Sep 17 00:00:00 2001
+From: NeilBrown <neilb@suse.de>
+Date: Thu, 2 Oct 2014 13:45:00 +1000
+Subject: md/raid5: disable 'DISCARD' by default due to safety concerns.
+
+From: NeilBrown <neilb@suse.de>
+
+commit 8e0e99ba64c7ba46133a7c8a3e3f7de01f23bd93 upstream.
+
+It has come to my attention (thanks Martin) that 'discard_zeroes_data'
+is only a hint.  Some devices in some cases don't do what it
+says on the label.
+
+The use of DISCARD in RAID5 depends on reads from discarded regions
+being predictably zero.  If a write to a previously discarded region
+performs a read-modify-write cycle it assumes that the parity block
+was consistent with the data blocks.  If all were zero, this would
+be the case.  If some are and some aren't this would not be the case.
+This could lead to data corruption after a device failure when
+data needs to be reconstructed from the parity.
+
+As we cannot trust 'discard_zeroes_data', ignore it by default
+and so disallow DISCARD on all raid4/5/6 arrays.
+
+As many devices are trustworthy, and as there are benefits to using
+DISCARD, add a module parameter to over-ride this caution and cause
+DISCARD to work if discard_zeroes_data is set.
+
+If a site want to enable DISCARD on some arrays but not on others they
+should select DISCARD support at the filesystem level, and set the
+raid456 module parameter.
+    raid456.devices_handle_discard_safely=Y
+
+As this is a data-safety issue, I believe this patch is suitable for
+-stable.
+DISCARD support for RAID456 was added in 3.7
+
+Cc: Shaohua Li <shli@kernel.org>
+Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
+Cc: Mike Snitzer <snitzer@redhat.com>
+Cc: Heinz Mauelshagen <heinzm@redhat.com>
+Cc: stable@vger.kernel.org (3.7+)
+Acked-by: Martin K. Petersen <martin.petersen@oracle.com>
+Acked-by: Mike Snitzer <snitzer@redhat.com>
+Fixes: 620125f2bf8ff0c4969b79653b54d7bcc9d40637
+Signed-off-by: NeilBrown <neilb@suse.de>
+[bwh: Backported to 3.10: adjust context]
+Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ drivers/md/raid5.c |   18 +++++++++++++++++-
+ 1 file changed, 17 insertions(+), 1 deletion(-)
+
+--- a/drivers/md/raid5.c
++++ b/drivers/md/raid5.c
+@@ -60,6 +60,10 @@
+ #include "raid0.h"
+ #include "bitmap.h"
+ 
++static bool devices_handle_discard_safely = false;
++module_param(devices_handle_discard_safely, bool, 0644);
++MODULE_PARM_DESC(devices_handle_discard_safely,
++               "Set to Y if all devices in each array reliably return zeroes on reads from discarded regions");
+ /*
+  * Stripe cache
+  */
+@@ -5611,7 +5615,7 @@ static int run(struct mddev *mddev)
+               mddev->queue->limits.discard_granularity = stripe;
+               /*
+                * unaligned part of discard request will be ignored, so can't
+-               * guarantee discard_zerors_data
++               * guarantee discard_zeroes_data
+                */
+               mddev->queue->limits.discard_zeroes_data = 0;
+ 
+@@ -5636,6 +5640,18 @@ static int run(struct mddev *mddev)
+                           !bdev_get_queue(rdev->bdev)->
+                                               limits.discard_zeroes_data)
+                               discard_supported = false;
++                      /* Unfortunately, discard_zeroes_data is not currently
++                       * a guarantee - just a hint.  So we only allow DISCARD
++                       * if the sysadmin has confirmed that only safe devices
++                       * are in use by setting a module parameter.
++                       */
++                      if (!devices_handle_discard_safely) {
++                              if (discard_supported) {
++                                      pr_info("md/raid456: discard support disabled due to uncertainty.\n");
++                                      pr_info("Set raid456.devices_handle_discard_safely=Y to override.\n");
++                              }
++                              discard_supported = false;
++                      }
+               }
+ 
+               if (discard_supported &&

diff --git a/queue-3.10/series b/queue-3.10/series
index a2db7bc7032ee73bc6b65c1101294332f0d4beed..ead932062bbb4f42e199ed5e029c6f43d7d8fc41 100644 (file)
--- a/queue-3.10/series
+++ b/queue-3.10/series
@@ -5,3 +5,4 @@ ring-buffer-fix-infinite-spin-in-reading-buffer.patch
 mm-thp-move-invariant-bug-check-out-of-loop-in-__split_huge_page_map.patch
 mm-numa-do-not-mark-ptes-pte_numa-when-splitting-huge-pages.patch
 media-vb2-fix-vbi-poll-regression.patch
+md-raid5-disable-discard-by-default-due-to-safety-concerns.patch