Patchwork [3.11,125/272] dm: allocate buffer for messages with small number of arguments using GFP_NOIO

login
register
mail settings
Submitter Luis Henriques
Date Dec. 6, 2013, 12:56 p.m.
Message ID <1386334761-25517-126-git-send-email-luis.henriques@canonical.com>
Download mbox | patch
Permalink /patch/297843/
State New
Headers show

Comments

Luis Henriques - Dec. 6, 2013, 12:56 p.m.
3.11.10.1 -stable review patch.  If anyone has any objections, please let me know.

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

From: Mikulas Patocka <mpatocka@redhat.com>

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

Patch

diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index f221812..bbd7369 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -545,14 +545,28 @@  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;