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

From: Jesper Juhl
Date: Mon Dec 13 2010 - 18:57:16 EST

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@xxxxxxxxxxxxx>, Hank Janssen
> <hjanssen@xxxxxxxxxxxxx> 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@xxxxxxxxxxx> for pointing this out.
> > And thanks to Jesper Juhl <jj@xxxxxxxxxxxxx> and Ky Srinivasan
> > <ksrinivasan@xxxxxxxxxx> for suggesting a better implementation of
> > my original patch.
> >
> > Signed-off-by: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>
> > Signed-off-by: Hank Janssen <hjanssen@xxxxxxxxxxxxx>
> > Cc: Evgeniy Polyakov <zbr@xxxxxxxxxxx>
> > Cc: Jesper Juhl <jj@xxxxxxxxxxxxx>
> > Cc: Ky Srinivasan <ksrinivasan@xxxxxxxxxx>
> >
> > ---
> > 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@xxxxxxxxxxxxx> http://www.chaosbits.net/
Don't top-post http://www.catb.org/~esr/jargon/html/T/top-post.html
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