Re: [RFC PATCH net-next 2/4] switchdev: add fwd_mark generator helper

Scott Feldman
2015-06-14T17:50:34Z

On Sat, Jun 13, 2015 at 11:56 PM, Jiri Pirko <jiri@resnulli.us> wrote:
> Sat, Jun 13, 2015 at 08:04:28PM CEST, sfeldma@gmail.com wrote:
>>From: Scott Feldman <sfeldma@gmail.com>
>>
>>skb->fwd_mark and dev->fwd_mark are 32-bit and should be unique for device
>>and maybe even unique for a sub-set of ports within device, so add
>>switchdev helper function to generate unique marks based on driver-supplied
>>key. Typically, the driver would use device switch ID for key, and maybe
>>additional fields in key for grouped ports such as bridge ifindex. The key
>>can be of arbitrary length.
>>
>>The generator uses a global hash table to store fwd_marks hashed by key.
>>
>>Signed-off-by: Scott Feldman <sfeldma@gmail.com>

<snip>

>>+u32 switchdev_mark_get(void *key, size_t key_len)
>>+{
>>+ struct switchdev_mark_ht_entry {
>>+ struct hlist_node entry;
>>+ void *key;
>>+ size_t key_len;
>>+ u32 key_crc32;
>>+ u32 mark;
>>+ } *entry;
>>+ u32 key_crc32 = crc32(~0, key, key_len);
>>+ u32 mark = 0;
>>+ unsigned long flags;
>>+
>>+ spin_lock_irqsave(&switchdev_mark_lock, flags);
>
> I fail to see why _irqsave variant is needed here.

I don't know what context caller is in, so using most conservative
spinlock. Is there a better way?