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

Jesper Juhl jj at chaosbits.net
Mon Dec 13 23:50:48 UTC 2010


On Mon, 13 Dec 2010, Ky Srinivasan wrote:

> 
> 
> >>> On 12/13/2010 at  3:34 PM, in message
> <1292272498-29483-1-git-send-email-hjanssen at microsoft.com>, Hank Janssen
> <hjanssen at microsoft.com> 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.
> > 
> > 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 +258,16 @@ 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);
> Why are these allocations GFP_ATOMIC. Clearly this is in module loading context and you can afford to sleep. GFP_KERNEL should be fine.
> 

I actually also noticed this when I did my first review of the patch, but 
I didn't point it out since I thought that "there must be a good reason". 
But now that you point it out and I look at the code once more I can't 
actually think of a "good reason",, so I agree with you completely that 
these should just be GFP_KERNEL.

-- 
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.




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