Re: [PATCH v2 4/9] nilfs2: add kmem_cache for SUFILE cache nodes

[Andreas Rohner <andreas.rohner-hi6Y0CQ0nG0@public.gmane.org>]

On 2015-05-09 04:41, Ryusuke Konishi wrote:
> On Sun,  3 May 2015 12:05:17 +0200, Andreas Rohner wrote:
>> This patch adds a kmem_cache to efficiently allocate SUFILE cache nodes.
>> One cache node contains a certain number of unsigned 32 bit values and
>> either a list_head, to string a number of nodes together into a linked
>> list, or an rcu_head to be able to use the node with an rcu
>> callback.
>>
>> These cache nodes can be used to cache small changes to the SUFILE and
>> apply them later at segment construction.
>>
>> Signed-off-by: Andreas Rohner <andreas.rohner-hi6Y0CQ0nG0@public.gmane.org>
>> ---
>>  fs/nilfs2/sufile.h | 14 ++++++++++++++
>>  fs/nilfs2/super.c  | 14 ++++++++++++++
>>  2 files changed, 28 insertions(+)
>>
>> diff --git a/fs/nilfs2/sufile.h b/fs/nilfs2/sufile.h
>> index da78edf..520614f 100644
>> --- a/fs/nilfs2/sufile.h
>> +++ b/fs/nilfs2/sufile.h
>> @@ -28,6 +28,20 @@
>>  #include <linux/nilfs2_fs.h>
>>  #include "mdt.h"
>>  
>> +#define NILFS_SUFILE_CACHE_NODE_SHIFT	6
>> +#define NILFS_SUFILE_CACHE_NODE_COUNT	(1 << NILFS_SUFILE_CACHE_NODE_SHIFT)
>> +
>> +struct nilfs_sufile_cache_node {
>> +	__u32 values[NILFS_SUFILE_CACHE_NODE_COUNT];
>> +	union {
>> +		struct rcu_head rcu_head;
>> +		struct list_head list_head;
>> +	};
>> +	unsigned long index;
>> +};
>> +
>> +extern struct kmem_cache *nilfs_sufile_node_cachep;
>> +
>>  static inline int
>>  nilfs_sufile_live_blks_ext_supported(const struct inode *sufile)
>>  {
>> diff --git a/fs/nilfs2/super.c b/fs/nilfs2/super.c
>> index f47585b..97a30db 100644
>> --- a/fs/nilfs2/super.c
>> +++ b/fs/nilfs2/super.c
>> @@ -71,6 +71,7 @@ static struct kmem_cache *nilfs_inode_cachep;
>>  struct kmem_cache *nilfs_transaction_cachep;
>>  struct kmem_cache *nilfs_segbuf_cachep;
>>  struct kmem_cache *nilfs_btree_path_cache;
>> +struct kmem_cache *nilfs_sufile_node_cachep;
>>  
>>  static int nilfs_setup_super(struct super_block *sb, int is_mount);
>>  static int nilfs_remount(struct super_block *sb, int *flags, char *data);
>> @@ -1397,6 +1398,11 @@ static void nilfs_segbuf_init_once(void *obj)
>>  	memset(obj, 0, sizeof(struct nilfs_segment_buffer));
>>  }
>>  
>> +static void nilfs_sufile_cache_node_init_once(void *obj)
>> +{
>> +	memset(obj, 0, sizeof(struct nilfs_sufile_cache_node));
>> +}
>> +
> 
> Note that nilfs_sufile_cache_node_init_once() is only called when each
> cache entry is allocated first time.  It doesn't ensure each cache
> entry is clean when it will be allocated with kmem_cache_alloc()
> the second time and afterwards.

I kind of assumed it would be called for every object returned by
kmem_cache_alloc(). In that case I have to do the initialization in
nilfs_sufile_alloc_cache_node() and remove this function.

Regards,
Andreas Rohner

> Regards,
> Ryusuke Konishi
> 
>>  static void nilfs_destroy_cachep(void)
>>  {
>>  	/*
>> @@ -1413,6 +1419,8 @@ static void nilfs_destroy_cachep(void)
>>  		kmem_cache_destroy(nilfs_segbuf_cachep);
>>  	if (nilfs_btree_path_cache)
>>  		kmem_cache_destroy(nilfs_btree_path_cache);
>> +	if (nilfs_sufile_node_cachep)
>> +		kmem_cache_destroy(nilfs_sufile_node_cachep);
>>  }
>>  
>>  static int __init nilfs_init_cachep(void)
>> @@ -1441,6 +1449,12 @@ static int __init nilfs_init_cachep(void)
>>  	if (!nilfs_btree_path_cache)
>>  		goto fail;
>>  
>> +	nilfs_sufile_node_cachep = kmem_cache_create("nilfs_sufile_node_cache",
>> +			sizeof(struct nilfs_sufile_cache_node), 0, 0,
>> +			nilfs_sufile_cache_node_init_once);
>> +	if (!nilfs_sufile_node_cachep)
>> +		goto fail;
>> +
>>  	return 0;
>>  
>>  fail:
>> -- 
>> 2.3.7
>>
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