Re: [PATCH 2/5] netdevtap: Use common helper function to create unique tap name

[Laine Stump <laine@xxxxxxxxxx>]

On 12/4/20 2:01 AM, Shi Lei wrote:
> Simplify GenerateName/ReserveName for netdevtap by using common
> functions.
>
> Signed-off-by: Shi Lei <shi_lei@xxxxxxxxxxxxxx>
> ---
>   src/util/virnetdevtap.c | 58 +++--------------------------------------
>   1 file changed, 4 insertions(+), 54 deletions(-)
>
> diff --git a/src/util/virnetdevtap.c b/src/util/virnetdevtap.c
> index 198607b5..38b2f171 100644
> --- a/src/util/virnetdevtap.c
> +++ b/src/util/virnetdevtap.c
> @@ -55,9 +55,6 @@
>   
>   VIR_LOG_INIT("util.netdevtap");
>   
> -virMutex virNetDevTapCreateMutex = VIR_MUTEX_INITIALIZER;
> -static int virNetDevTapLastID = -1; /* not "unsigned" because callers use %d */
> -
>   
>   /**
>    * virNetDevTapReserveName:
> @@ -72,25 +69,7 @@ static int virNetDevTapLastID = -1; /* not "unsigned" because callers use %d */
>   void
>   virNetDevTapReserveName(const char *name)
>   {
> -    unsigned int id;
> -    const char *idstr = NULL;
> -
> -
> -    if (STRPREFIX(name, VIR_NET_GENERATED_TAP_PREFIX)) {
> -
> -        VIR_INFO("marking device in use: '%s'", name);
> -
> -        idstr = name + strlen(VIR_NET_GENERATED_TAP_PREFIX);
> -
> -        if (virStrToLong_ui(idstr, NULL, 10, &id) >= 0) {
> -            virMutexLock(&virNetDevTapCreateMutex);
> -
> -            if (virNetDevTapLastID < (int)id)
> -                virNetDevTapLastID = id;
> -
> -            virMutexUnlock(&virNetDevTapCreateMutex);
> -        }
> -    }
> +    virNetDevReserveName(name, VIR_NET_DEV_GEN_NAME_TAP, true);


I think we can just call virNetDevReserveName() directly, rather than 
keeping virNetDevTapReserveName() as a go-between...



>   }
>   
>   
> @@ -199,36 +178,7 @@ virNetDevTapGetRealDeviceName(char *ifname G_GNUC_UNUSED)
>   static int
>   virNetDevTapGenerateName(char **ifname)
>   {
> -    int id;
> -    double maxIDd = pow(10, IFNAMSIZ - 1 - strlen(VIR_NET_GENERATED_TAP_PREFIX));
> -    int maxID = INT_MAX;
> -    int attempts = 0;
> -
> -    if (maxIDd <= (double)INT_MAX)
> -        maxID = (int)maxIDd;
> -
> -    do {
> -        g_autofree char *try = NULL;
> -
> -        id = ++virNetDevTapLastID;
> -
> -        /* reset before overflow */
> -        if (virNetDevTapLastID >= maxID)
> -            virNetDevTapLastID = -1;
> -
> -        try = g_strdup_printf(*ifname, id);
> -
> -        if (!virNetDevExists(try)) {
> -            g_free(*ifname);
> -            *ifname = g_steal_pointer(&try);
> -            return 0;
> -        }
> -    } while (++attempts < 10000);
> -
> -    virReportError(VIR_ERR_INTERNAL_ERROR,
> -                   _("no unused %s names available"),
> -                   VIR_NET_GENERATED_TAP_PREFIX);
> -    return -1;
> +    return virNetDevGenerateName(ifname, VIR_NET_DEV_GEN_NAME_TAP);


Same here.


>   }
>   
>   
> @@ -263,7 +213,7 @@ int virNetDevTapCreate(char **ifname,
>       int ret = -1;
>       int fd = -1;
>   
> -    virMutexLock(&virNetDevTapCreateMutex);
> +    virNetDevLockGenName(VIR_NET_DEV_GEN_NAME_TAP);
>   
>       /* if ifname is "vnet%d", then auto-generate a name for the new
>        * device (the kernel could do this for us, but has a bad habit of


The code around here is going to need to be updated to take advantage of 
the "g_strdup_printf(*ifname, id)" in your new Generate function. (as a 
matter of fact, the functions that call virNetDevTapCreate() should 
probably also be updated to stop them from adding in "vnet%d" when 
ifname is empty - we can just let it remain empty until the call to 
virNetDevGenerateName().


> @@ -333,7 +283,7 @@ int virNetDevTapCreate(char **ifname,
>       ret = 0;
>   
>    cleanup:
> -    virMutexUnlock(&virNetDevTapCreateMutex);
> +    virNetDevUnlockGenName(VIR_NET_DEV_GEN_NAME_TAP);
>       if (ret < 0) {
>           VIR_FORCE_CLOSE(fd);
>           while (i--)