[3.5.y.z extended stable] Patch "dm: allocate buffer for messages with small number of arguments using" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    dm: allocate buffer for messages with small number of arguments using

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From d1801f79d595ed0b788e8ddf6c1ca85f76dc3b16 Mon Sep 17 00:00:00 2001
From: Mikulas Patocka <mpatocka at redhat.com>
Date: Thu, 31 Oct 2013 13:55:45 -0400
Subject: dm: allocate buffer for messages with small number of arguments using
 GFP_NOIO

commit f36afb3957353d2529cb2b00f78fdccd14fc5e9c upstream.

dm-mpath and dm-thin must process messages even if some device is
suspended, so we allocate argv buffer with GFP_NOIO. These messages have
a small fixed number of arguments.

On the other hand, dm-switch needs to process bulk data using messages
so excessive use of GFP_NOIO could cause trouble.

The patch also lowers the default number of arguments from 64 to 8, so
that there is smaller load on GFP_NOIO allocations.

Signed-off-by: Mikulas Patocka <mpatocka at redhat.com>
Acked-by: Alasdair G Kergon <agk at redhat.com>
Signed-off-by: Mike Snitzer <snitzer at redhat.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/md/dm-table.c | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index f220a69..d509f23 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -581,14 +581,28 @@ static int adjoin(struct dm_table *table, struct dm_target *ti)

 /*
  * Used to dynamically allocate the arg array.
+ *
+ * We do first allocation with GFP_NOIO because dm-mpath and dm-thin must
+ * process messages even if some device is suspended. These messages have a
+ * small fixed number of arguments.
+ *
+ * On the other hand, dm-switch needs to process bulk data using messages and
+ * excessive use of GFP_NOIO could cause trouble.
  */
 static char **realloc_argv(unsigned *array_size, char **old_argv)
 {
 	char **argv;
 	unsigned new_size;
+	gfp_t gfp;

-	new_size = *array_size ? *array_size * 2 : 64;
-	argv = kmalloc(new_size * sizeof(*argv), GFP_KERNEL);
+	if (*array_size) {
+		new_size = *array_size * 2;
+		gfp = GFP_KERNEL;
+	} else {
+		new_size = 8;
+		gfp = GFP_NOIO;
+	}
+	argv = kmalloc(new_size * sizeof(*argv), gfp);
 	if (argv) {
 		memcpy(argv, old_argv, *array_size * sizeof(*argv));
 		*array_size = new_size;
--
1.8.3.2