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Subject[PATCH v2 2/5] Drivers: hv: allocate the exact needed memory for messages
Date
When we need to pass a buffer with Hyper-V message we don't need to always
allocate 256 bytes for the message: the real message length is known from
the header. Change 'struct onmessage_work_context' to make it possible to
not over-allocate.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
---
drivers/hv/vmbus_drv.c | 15 ++++++++++-----
1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index 943b23beb992..b114bb411d7e 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -991,7 +991,10 @@ static struct bus_type hv_bus = {

struct onmessage_work_context {
struct work_struct work;
- struct hv_message msg;
+ struct {
+ struct hv_message_header header;
+ u8 payload[];
+ } msg;
};

static void vmbus_onmessage_work(struct work_struct *work)
@@ -1044,7 +1047,8 @@ void vmbus_on_msg_dpc(unsigned long data)
goto msg_handled;

if (entry->handler_type == VMHT_BLOCKING) {
- ctx = kmalloc(sizeof(*ctx), GFP_ATOMIC);
+ ctx = kmalloc(sizeof(*ctx) + msg->header.payload_size,
+ GFP_ATOMIC);
if (ctx == NULL)
return;

@@ -1098,10 +1102,11 @@ static void vmbus_force_channel_rescinded(struct vmbus_channel *channel)
WARN_ON(!is_hvsock_channel(channel));

/*
- * sizeof(*ctx) is small and the allocation should really not fail,
+ * Allocation size is small and the allocation should really not fail,
* otherwise the state of the hv_sock connections ends up in limbo.
*/
- ctx = kzalloc(sizeof(*ctx), GFP_KERNEL | __GFP_NOFAIL);
+ ctx = kzalloc(sizeof(*ctx) + sizeof(*rescind),
+ GFP_KERNEL | __GFP_NOFAIL);

/*
* So far, these are not really used by Linux. Just set them to the
@@ -1111,7 +1116,7 @@ static void vmbus_force_channel_rescinded(struct vmbus_channel *channel)
ctx->msg.header.payload_size = sizeof(*rescind);

/* These values are actually used by Linux. */
- rescind = (struct vmbus_channel_rescind_offer *)ctx->msg.u.payload;
+ rescind = (struct vmbus_channel_rescind_offer *)ctx->msg.payload;
rescind->header.msgtype = CHANNELMSG_RESCIND_CHANNELOFFER;
rescind->child_relid = channel->offermsg.child_relid;

--
2.25.1
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