netdev - Re: [RFC PATCH net-next 2/4] switchdev: add fwd

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Message-ID: <CAE4R7bCABXELpMjqL1x1qyRy11JGmtMGZ6-Yo_5hXbWuFFF8_Q@mail.gmail.com>
Date:	Mon, 15 Jun 2015 06:52:47 -0700
From:	Scott Feldman <sfeldma@...il.com>
To:	Jiri Pirko <jiri@...nulli.us>
Cc:	Netdev <netdev@...r.kernel.org>,
	"simon.horman@...ronome.com" <simon.horman@...ronome.com>,
	Roopa Prabhu <roopa@...ulusnetworks.com>,
	"Arad, Ronen" <ronen.arad@...el.com>,
	"Fastabend, John R" <john.r.fastabend@...el.com>,
	"andrew@...n.ch" <andrew@...n.ch>,
	Florian Fainelli <f.fainelli@...il.com>,
	Guenter Roeck <linux@...ck-us.net>,
	davidch <davidch@...adcom.com>,
	"stephen@...workplumber.org" <stephen@...workplumber.org>
Subject: Re: [RFC PATCH net-next 2/4] switchdev: add fwd_mark generator helper

On Sun, Jun 14, 2015 at 10:46 PM, Jiri Pirko <jiri@...nulli.us> wrote:
> Sun, Jun 14, 2015 at 07:50:13PM CEST, sfeldma@...il.com wrote:
>>On Sat, Jun 13, 2015 at 11:56 PM, Jiri Pirko <jiri@...nulli.us> wrote:
>>> Sat, Jun 13, 2015 at 08:04:28PM CEST, sfeldma@...il.com wrote:
>>>>From: Scott Feldman <sfeldma@...il.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@...il.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.
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