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

[Scott Feldman <sfeldma@gmail.com>]

On Sun, Jun 14, 2015 at 10:46 PM, Jiri Pirko <jiri@resnulli.us> wrote:
> Sun, Jun 14, 2015 at 07:50:13PM CEST, sfeldma@gmail.com wrote:
>>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?
>
> I don't see why would someone call this from irq.

Ok, good point, I'll adjust to spin_lock.