thr3ads.net - Linux Virtualization - [PATCH 1/1] hv: Use only one txf buffer per channel and kmalloc on initialize [Dec 2010]

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Hank Janssen

2010-Dec-13 21:14 UTC

[PATCH 1/1] hv: Use only one txf buffer per channel and kmalloc on initialize

Correct issue with not checking kmalloc return value.
This fix now only uses one receive buffer for all hv_utils 
channels, and will do only one kmalloc on init and will return
with a -ENOMEM if kmalloc fails on initialize.

And properly clean up memory on failure.

Thanks to Evgeniy Polyakov <zbr at ioremap.net> for pointing this out.
And thanks to Jesper Juhl <jj at chaosbits.net> and Ky Srinivasan 
<ksrinivasan at novell.com> for suggesting a better implementation of
my original patch.

Signed-off-by: Haiyang Zhang <haiyangz at microsoft.com>
Signed-off-by: Hank Janssen <hjanssen at microsoft.com>
Cc: Evgeniy Polyakov <zbr at ioremap.net>
Cc: Jesper Juhl <jj at chaosbits.net>
Cc: Ky Srinivasan <ksrinivasan at novell.com>

---
 drivers/staging/hv/hv_utils.c |   84 +++++++++++++++++++++-------------------
 1 files changed, 44 insertions(+), 40 deletions(-)

diff --git a/drivers/staging/hv/hv_utils.c b/drivers/staging/hv/hv_utils.c
index 53e1e29..e0ecc23 100644
--- a/drivers/staging/hv/hv_utils.c
+++ b/drivers/staging/hv/hv_utils.c
@@ -38,12 +38,14 @@
 #include "vmbus_api.h"
 #include "utils.h"
 
+static u8 *shut_txf_buf;
+static u8 *time_txf_buf;
+static u8 *hbeat_txf_buf;
 
 static void shutdown_onchannelcallback(void *context)
 {
 	struct vmbus_channel *channel = context;
-	u8 *buf;
-	u32 buflen, recvlen;
+	u32 recvlen;
 	u64 requestid;
 	u8  execute_shutdown = false;
 
@@ -52,24 +54,23 @@ static void shutdown_onchannelcallback(void *context)
 	struct icmsg_hdr *icmsghdrp;
 	struct icmsg_negotiate *negop = NULL;
 
-	buflen = PAGE_SIZE;
-	buf = kmalloc(buflen, GFP_ATOMIC);
-
-	vmbus_recvpacket(channel, buf, buflen, &recvlen, &requestid);
+	vmbus_recvpacket(channel, shut_txf_buf,
+			 PAGE_SIZE, &recvlen, &requestid);
 
 	if (recvlen > 0) {
 		DPRINT_DBG(VMBUS, "shutdown packet: len=%d, requestid=%lld",
 			   recvlen, requestid);
 
-		icmsghdrp = (struct icmsg_hdr *)&buf[
+		icmsghdrp = (struct icmsg_hdr *)&shut_txf_buf[
 			sizeof(struct vmbuspipe_hdr)];
 
 		if (icmsghdrp->icmsgtype == ICMSGTYPE_NEGOTIATE) {
-			prep_negotiate_resp(icmsghdrp, negop, buf);
+			prep_negotiate_resp(icmsghdrp, negop, shut_txf_buf);
 		} else {
-			shutdown_msg = (struct shutdown_msg_data *)&buf[
-				sizeof(struct vmbuspipe_hdr) +
-				sizeof(struct icmsg_hdr)];
+			shutdown_msg +				(struct shutdown_msg_data *)&shut_txf_buf[
+					sizeof(struct vmbuspipe_hdr) +
+					sizeof(struct icmsg_hdr)];
 
 			switch (shutdown_msg->flags) {
 			case 0:
@@ -93,13 +94,11 @@ static void shutdown_onchannelcallback(void *context)
 		icmsghdrp->icflags = ICMSGHDRFLAG_TRANSACTION
 			| ICMSGHDRFLAG_RESPONSE;
 
-		vmbus_sendpacket(channel, buf,
+		vmbus_sendpacket(channel, shut_txf_buf,
 				       recvlen, requestid,
 				       VmbusPacketTypeDataInBand, 0);
 	}
 
-	kfree(buf);
-
 	if (execute_shutdown == true)
 		orderly_poweroff(false);
 }
@@ -150,28 +149,25 @@ static inline void adj_guesttime(u64 hosttime, u8 flags)
 static void timesync_onchannelcallback(void *context)
 {
 	struct vmbus_channel *channel = context;
-	u8 *buf;
-	u32 buflen, recvlen;
+	u32 recvlen;
 	u64 requestid;
 	struct icmsg_hdr *icmsghdrp;
 	struct ictimesync_data *timedatap;
 
-	buflen = PAGE_SIZE;
-	buf = kmalloc(buflen, GFP_ATOMIC);
-
-	vmbus_recvpacket(channel, buf, buflen, &recvlen, &requestid);
+	vmbus_recvpacket(channel, time_txf_buf,
+			 PAGE_SIZE, &recvlen, &requestid);
 
 	if (recvlen > 0) {
 		DPRINT_DBG(VMBUS, "timesync packet: recvlen=%d, requestid=%lld",
 			recvlen, requestid);
 
-		icmsghdrp = (struct icmsg_hdr *)&buf[
+		icmsghdrp = (struct icmsg_hdr *)&time_txf_buf[
 				sizeof(struct vmbuspipe_hdr)];
 
 		if (icmsghdrp->icmsgtype == ICMSGTYPE_NEGOTIATE) {
-			prep_negotiate_resp(icmsghdrp, NULL, buf);
+			prep_negotiate_resp(icmsghdrp, NULL, time_txf_buf);
 		} else {
-			timedatap = (struct ictimesync_data *)&buf[
+			timedatap = (struct ictimesync_data *)&time_txf_buf[
 				sizeof(struct vmbuspipe_hdr) +
 				sizeof(struct icmsg_hdr)];
 			adj_guesttime(timedatap->parenttime, timedatap->flags);
@@ -180,12 +176,10 @@ static void timesync_onchannelcallback(void *context)
 		icmsghdrp->icflags = ICMSGHDRFLAG_TRANSACTION
 			| ICMSGHDRFLAG_RESPONSE;
 
-		vmbus_sendpacket(channel, buf,
+		vmbus_sendpacket(channel, time_txf_buf,
 				recvlen, requestid,
 				VmbusPacketTypeDataInBand, 0);
 	}
-
-	kfree(buf);
 }
 
 /*
@@ -196,30 +190,28 @@ static void timesync_onchannelcallback(void *context)
 static void heartbeat_onchannelcallback(void *context)
 {
 	struct vmbus_channel *channel = context;
-	u8 *buf;
-	u32 buflen, recvlen;
+	u32 recvlen;
 	u64 requestid;
 	struct icmsg_hdr *icmsghdrp;
 	struct heartbeat_msg_data *heartbeat_msg;
 
-	buflen = PAGE_SIZE;
-	buf = kmalloc(buflen, GFP_ATOMIC);
-
-	vmbus_recvpacket(channel, buf, buflen, &recvlen, &requestid);
+	vmbus_recvpacket(channel, hbeat_txf_buf,
+			 PAGE_SIZE, &recvlen, &requestid);
 
 	if (recvlen > 0) {
 		DPRINT_DBG(VMBUS, "heartbeat packet: len=%d, requestid=%lld",
 			   recvlen, requestid);
 
-		icmsghdrp = (struct icmsg_hdr *)&buf[
+		icmsghdrp = (struct icmsg_hdr *)&hbeat_txf_buf[
 				sizeof(struct vmbuspipe_hdr)];
 
 		if (icmsghdrp->icmsgtype == ICMSGTYPE_NEGOTIATE) {
-			prep_negotiate_resp(icmsghdrp, NULL, buf);
+			prep_negotiate_resp(icmsghdrp, NULL, hbeat_txf_buf);
 		} else {
-			heartbeat_msg = (struct heartbeat_msg_data *)&buf[
-				sizeof(struct vmbuspipe_hdr) +
-				sizeof(struct icmsg_hdr)];
+			heartbeat_msg +				(struct heartbeat_msg_data *)&hbeat_txf_buf[
+					sizeof(struct vmbuspipe_hdr) +
+					sizeof(struct icmsg_hdr)];
 
 			DPRINT_DBG(VMBUS, "heartbeat seq = %lld",
 				   heartbeat_msg->seq_num);
@@ -230,12 +222,10 @@ static void heartbeat_onchannelcallback(void *context)
 		icmsghdrp->icflags = ICMSGHDRFLAG_TRANSACTION
 			| ICMSGHDRFLAG_RESPONSE;
 
-		vmbus_sendpacket(channel, buf,
+		vmbus_sendpacket(channel, hbeat_txf_buf,
 				       recvlen, requestid,
 				       VmbusPacketTypeDataInBand, 0);
 	}
-
-	kfree(buf);
 }
 
 static const struct pci_device_id __initconst
@@ -268,6 +258,19 @@ static int __init init_hyperv_utils(void)
 	if (!dmi_check_system(hv_utils_dmi_table))
 		return -ENODEV;
 
+	shut_txf_buf = kmalloc(PAGE_SIZE, GFP_ATOMIC);
+	time_txf_buf = kmalloc(PAGE_SIZE, GFP_ATOMIC);
+	hbeat_txf_buf = kmalloc(PAGE_SIZE, GFP_ATOMIC);
+
+	if (!shut_txf_buf || !time_txf_buf || !hbeat_txf_buf) {
+		printk(KERN_INFO
+		       "Unable to allocate memory for receive buffer\n");
+		kfree(shut_txf_buf);
+		kfree(time_txf_buf);
+		kfree(hbeat_txf_buf);
+		return -ENOMEM;
+	}
+
 	hv_cb_utils[HV_SHUTDOWN_MSG].channel->onchannel_callback  	
&shutdown_onchannelcallback;
 	hv_cb_utils[HV_SHUTDOWN_MSG].callback = &shutdown_onchannelcallback;
@@ -298,6 +298,10 @@ static void exit_hyperv_utils(void)
 	hv_cb_utils[HV_HEARTBEAT_MSG].channel->onchannel_callback  	
&chn_cb_negotiate;
 	hv_cb_utils[HV_HEARTBEAT_MSG].callback = &chn_cb_negotiate;
+
+	kfree(shut_txf_buf);
+	kfree(time_txf_buf);
+	kfree(hbeat_txf_buf);
 }
 
 module_init(init_hyperv_utils);
-- 
1.6.0.2

Jesper Juhl

2010-Dec-13 21:22 UTC

head link

[PATCH 1/1] hv: Use only one txf buffer per channel and kmalloc on initialize

On Mon, 13 Dec 2010, Hank Janssen wrote:
> Correct issue with not checking kmalloc return value.
> This fix now only uses one receive buffer for all hv_utils 
> channels, and will do only one kmalloc on init and will return
> with a -ENOMEM if kmalloc fails on initialize.
> 
> And properly clean up memory on failure.
> 
> Thanks to Evgeniy Polyakov <zbr at ioremap.net> for pointing this
out.
> And thanks to Jesper Juhl <jj at chaosbits.net> and Ky Srinivasan 
> <ksrinivasan at novell.com> for suggesting a better implementation of
> my original patch.
> 
> Signed-off-by: Haiyang Zhang <haiyangz at microsoft.com>
> Signed-off-by: Hank Janssen <hjanssen at microsoft.com>
> Cc: Evgeniy Polyakov <zbr at ioremap.net>
> Cc: Jesper Juhl <jj at chaosbits.net>
> Cc: Ky Srinivasan <ksrinivasan at novell.com>
> 
I can't spot any problems with these changes now, so feel free to add
  Reviewed-by: Jesper Juhl <jj at chaosbits.net>
if you like.


-- 
Jesper Juhl <jj at chaosbits.net>            http://www.chaosbits.net/
Don't top-post http://www.catb.org/~esr/jargon/html/T/top-post.html
Plain text mails only, please.

Evgeniy Polyakov

2010-Dec-13 22:03 UTC

head link

[PATCH 1/1] hv: Use only one txf buffer per channel and kmalloc on initialize

On Mon, Dec 13, 2010 at 01:14:21PM -0800, Hank Janssen (hjanssen at
microsoft.com) wrote:> +static u8 *shut_txf_buf;
> +static u8 *time_txf_buf;
> +static u8 *hbeat_txf_buf;
Those are accessed without any kind of synchronization. I do not know
exact context, but are you sure it is single-threaded?

-- 
	Evgeniy Polyakov

Hank Janssen

2010-Dec-13 22:57 UTC

head link

[PATCH 1/1] hv: Use only one txf buffer per channel and kmalloc on initialize

-----Original Message----->From: Evgeniy Polyakov [mailto:zbr at ioremap.net] 
>Sent: Monday, December 13, 2010 2:04 PM
>
>On Mon, Dec 13, 2010 at 01:14:21PM -0800, Hank Janssen (hjanssen at
microsoft.com) wrote:
>> +static u8 *shut_txf_buf;
>> +static u8 *time_txf_buf;
>> +static u8 *hbeat_txf_buf;
>
>Those are accessed without any kind of synchronization. I do not know exact
context, but are you sure it is single-threaded?
The hv_utils driver services are all single threaded. The other drivers are not,
but this one is.

Hank.

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