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Message-ID: <20090611192037.GA5116@mit.edu>
Date: Thu, 11 Jun 2009 15:20:37 -0400
From: Theodore Tso <tytso@....edu>
To: Frederic Weisbecker <fweisbec@...il.com>
Cc: Christoph Hellwig <hch@...radead.org>,
Steven Rostedt <rostedt@...dmis.org>,
Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
Andrew Morton <akpm@...ux-foundation.org>,
Minchan Kim <minchan.kim@...il.com>,
Mel Gorman <mel@....ul.ie>, Rik van Riel <riel@...hat.com>,
Pekka Enberg <penberg@...helsinki.fi>,
Peter Zijlstra <peterz@...radead.org>,
Mathieu Desnoyers <compudj@...stal.dyndns.org>,
Lai Jiangshan <laijs@...fujitsu.com>,
Zhaolei <zhaolei@...fujitsu.com>,
KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
Jason Baron <jbaron@...hat.com>,
Jiaying Zhang <jiayingz@...gle.com>,
Tom Zanussi <tzanussi@...il.com>,
Xiao Guangrong <xiaoguangrong@...fujitsu.com>
Subject: Re: [PATCH 00/11] [GIT PULL] more updates for the tag format
On Thu, Jun 11, 2009 at 07:14:36PM +0200, Frederic Weisbecker wrote:
>
> For the filters, we could enter the text name which would be
> internally converted into a dev_t, there should be no problem.
>
> Also the raw dev_t can be stored and then human-friendly printed on
> print time.
>
> Both seem about trivial to add.
If someone wants to take this code and drop it into the core tracing
code, please feel free.
- Ted
/*
* jbd2_dev_to_name is a utility function used by the jbd2 and ext4
* tracing infrastructure to map a dev_t to a device name.
*
* The caller should use rcu_read_lock() in order to make sure the
* device name stays valid until its done with it. We use
* rcu_read_lock() as well to make sure we're safe in case the caller
* gets sloppy, and because rcu_read_lock() is cheap and can be safely
* nested.
*/
struct devname_cache {
struct rcu_head rcu;
dev_t device;
char devname[BDEVNAME_SIZE];
};
#define CACHE_SIZE_BITS 6
static struct devname_cache *devcache[1 << CACHE_SIZE_BITS];
static DEFINE_SPINLOCK(devname_cache_lock);
static void free_devcache(struct rcu_head *rcu)
{
kfree(rcu);
}
const char *jbd2_dev_to_name(dev_t device)
{
int i = hash_32(device, CACHE_SIZE_BITS);
char *ret;
struct block_device *bd;
rcu_read_lock();
if (devcache[i] && devcache[i]->device == device) {
ret = devcache[i]->devname;
rcu_read_unlock();
return ret;
}
rcu_read_unlock();
spin_lock(&devname_cache_lock);
if (devcache[i]) {
if (devcache[i]->device == device) {
ret = devcache[i]->devname;
spin_unlock(&devname_cache_lock);
return ret;
}
call_rcu(&devcache[i]->rcu, free_devcache);
}
devcache[i] = kmalloc(sizeof(struct devname_cache), GFP_KERNEL);
if (!devcache[i]) {
spin_unlock(&devname_cache_lock);
return "NODEV-ALLOCFAILURE"; /* Something non-NULL */
}
devcache[i]->device = device;
bd = bdget(device);
if (bd) {
bdevname(bd, devcache[i]->devname);
bdput(bd);
} else
__bdevname(device, devcache[i]->devname);
ret = devcache[i]->devname;
spin_unlock(&devname_cache_lock);
return ret;
}
EXPORT_SYMBOL(jbd2_dev_to_name);
--
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