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>

Author: Ian Campbell

drivers/block/xen-blkfront.c

@@ -584,7 +584,7 @@ static int setup_blkring(struct xenbus_device *dev,
 
 	info->ring_ref = GRANT_INVALID_REF;
 
-	sring = (struct blkif_sring *)__get_free_page(GFP_KERNEL);
+	sring = (struct blkif_sring *)__get_free_page(GFP_NOIO | __GFP_HIGH);
 	if (!sring) {
 		xenbus_dev_fatal(dev, -ENOMEM, "allocating shared ring");
 		return -ENOMEM;
@@ -741,7 +741,8 @@ static int blkif_recover(struct blkfront_info *info)
 	int j;
 
 	/* Stage 1: Make a safe copy of the shadow state. */
-	copy = kmalloc(sizeof(info->shadow), GFP_KERNEL);
+	copy = kmalloc(sizeof(info->shadow),
+		       GFP_NOIO | __GFP_REPEAT | __GFP_HIGH);
 	if (!copy)
 		return -ENOMEM;
 	memcpy(copy, info->shadow, sizeof(info->shadow));

drivers/net/xen-netfront.c

@@ -1324,7 +1324,7 @@ static int setup_netfront(struct xenbus_device *dev, struct netfront_info *info)
 		goto fail;
 	}
 
-	txs = (struct xen_netif_tx_sring *)get_zeroed_page(GFP_KERNEL);
+	txs = (struct xen_netif_tx_sring *)get_zeroed_page(GFP_NOIO | __GFP_HIGH);
 	if (!txs) {
 		err = -ENOMEM;
 		xenbus_dev_fatal(dev, err, "allocating tx ring page");
@@ -1340,7 +1340,7 @@ static int setup_netfront(struct xenbus_device *dev, struct netfront_info *info)
 	}
 
 	info->tx_ring_ref = err;
-	rxs = (struct xen_netif_rx_sring *)get_zeroed_page(GFP_KERNEL);
+	rxs = (struct xen_netif_rx_sring *)get_zeroed_page(GFP_NOIO | __GFP_HIGH);
 	if (!rxs) {
 		err = -ENOMEM;
 		xenbus_dev_fatal(dev, err, "allocating rx ring page");

drivers/xen/xenbus/xenbus_client.c

@@ -117,7 +117,7 @@ int xenbus_watch_pathfmt(struct xenbus_device *dev,
 	char *path;
 
 	va_start(ap, pathfmt);
-	path = kvasprintf(GFP_KERNEL, pathfmt, ap);
+	path = kvasprintf(GFP_NOIO | __GFP_HIGH, pathfmt, ap);
 	va_end(ap);
 
 	if (!path) {

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;