xen: Avoid allocations causing swap activity on the resume path

Avoid allocations causing swap activity on the resume path by
preventing the allocations from doing IO and allowing them
to access the emergency pools.

These paths are used when a frontend device is trying to connect
to its backend driver over Xenbus.  These reconnections are triggered
on demand by IO, so by definition there is already IO underway,
and further IO would naturally deadlock.  On resume, this path
is triggered when the running system tries to continue using its
devices.  If it cannot then the resume will fail; to try to avoid this
we let it dip into the emergency pools.

[ linux-2.6.18-xen changesets e8b49cfbdac, fdb998e79aba ]

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 5 insertions, 5 deletions

diff --git a/drivers/xen/xenbus/xenbus_xs.c b/drivers/xen/xenbus/xenbus_xs.c
index 227d53b12a5c..7f2f91c0e11d 100644
--- a/drivers/xen/xenbus/xenbus_xs.c
+++ b/drivers/xen/xenbus/xenbus_xs.c
@@ -283,9 +283,9 @@ static char *join(const char *dir, const char *name)
         char *buffer;
 
         if (strlen(name) == 0)
-                buffer = kasprintf(GFP_KERNEL, "%s", dir);
+                buffer = kasprintf(GFP_NOIO | __GFP_HIGH, "%s", dir);
         else
-                buffer = kasprintf(GFP_KERNEL, "%s/%s", dir, name);
+                buffer = kasprintf(GFP_NOIO | __GFP_HIGH, "%s/%s", dir, name);
         return (!buffer) ? ERR_PTR(-ENOMEM) : buffer;
 }
 
@@ -297,7 +297,7 @@ static char **split(char *strings, unsigned int len, unsigned int *num)
         *num = count_strings(strings, len);
 
         /* Transfer to one big alloc for easy freeing. */
-        ret = kmalloc(*num * sizeof(char *) + len, GFP_KERNEL);
+        ret = kmalloc(*num * sizeof(char *) + len, GFP_NOIO | __GFP_HIGH);
         if (!ret) {
                 kfree(strings);
                 return ERR_PTR(-ENOMEM);
@@ -751,7 +751,7 @@ static int process_msg(void)
         }
 
 
-        msg = kmalloc(sizeof(*msg), GFP_KERNEL);
+        msg = kmalloc(sizeof(*msg), GFP_NOIO | __GFP_HIGH);
         if (msg == NULL) {
                 err = -ENOMEM;
                 goto out;
@@ -763,7 +763,7 @@ static int process_msg(void)
                 goto out;
         }
 
-        body = kmalloc(msg->hdr.len + 1, GFP_KERNEL);
+        body = kmalloc(msg->hdr.len + 1, GFP_NOIO | __GFP_HIGH);
         if (body == NULL) {
                 kfree(msg);
                 err = -ENOMEM;