Re: [RFC 1/3] SQUASHME: Generalize the device cache so it can be used by all layouts

[Boaz Harrosh <bharrosh@panasas.com>]

On 09/12/2010 09:42 PM, Trond Myklebust wrote:
> On Sun, 2010-09-12 at 19:03 +0200, Boaz Harrosh wrote:
>> Current code thinks that there can be a single device_id per
>> layout segment. Change that to assume no relations between segments
>> and device_ids. It's now up to the layout-driver to make any relations.
>>
>> Files layout driver is fixed in next patch.
>>
>> Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>
>> ---
>>  fs/nfs/pnfs.c             |   20 +++++---------------
>>  include/linux/nfs4_pnfs.h |    6 +-----
>>  2 files changed, 6 insertions(+), 20 deletions(-)
>>
>> diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
>> index eb4e092..f26abc0 100644
>> --- a/fs/nfs/pnfs.c
>> +++ b/fs/nfs/pnfs.c
>> @@ -1892,26 +1892,16 @@ nfs4_init_deviceid_node(struct nfs4_deviceid *d)
>>  }
>>  EXPORT_SYMBOL(nfs4_init_deviceid_node);
>>  
>> -/* Called from layoutdriver_io_operations->alloc_lseg */
>> -void
>> -nfs4_set_layout_deviceid(struct pnfs_layout_segment *l, struct nfs4_deviceid *d)
>> -{
>> -	dprintk("%s [%d]\n", __func__, atomic_read(&d->de_kref.refcount));
>> -	l->deviceid = d;
>> -}
>> -EXPORT_SYMBOL(nfs4_set_layout_deviceid);
>> -
>>  /* Called from layoutdriver_io_operations->free_lseg */
>>  void
>> -nfs4_put_unset_layout_deviceid(struct pnfs_layout_segment *l,
>> -			   struct nfs4_deviceid *d,
>> -			   void (*free_callback)(struct kref *))
>> +nfs4_put_deviceid(struct nfs4_deviceid_cache *c,
>> +			   struct nfs4_deviceid *d)
>>  {
>>  	dprintk("%s [%d]\n", __func__, atomic_read(&d->de_kref.refcount));
>> -	l->deviceid = NULL;
>> -	kref_put(&d->de_kref, free_callback);
>> +	kref_put(&d->de_kref, c->dc_free_callback);
>> +	/* Do we need to return the deviceid_cache ref */
>>  }
>> -EXPORT_SYMBOL(nfs4_put_unset_layout_deviceid);
>> +EXPORT_SYMBOL(nfs4_put_deviceid);
>>  
>>  /* Find and reference a deviceid */
>>  struct nfs4_deviceid *
>> diff --git a/include/linux/nfs4_pnfs.h b/include/linux/nfs4_pnfs.h
>> index 577cd2b..dc3410e 100644
>> --- a/include/linux/nfs4_pnfs.h
>> +++ b/include/linux/nfs4_pnfs.h
>> @@ -111,7 +111,6 @@ struct pnfs_layout_segment {
>>  	struct kref kref;
>>  	bool valid;
>>  	struct pnfs_layout_hdr *layout;
>> -	struct nfs4_deviceid *deviceid;
>>  	u8 ld_data[];			/* layout driver private data */
>>  };
>>  
>> @@ -287,11 +286,8 @@ extern struct nfs4_deviceid *nfs4_find_get_deviceid(
>>  				struct pnfs_deviceid *);
>>  extern struct nfs4_deviceid *nfs4_add_get_deviceid(struct nfs4_deviceid_cache *,
>>  				struct nfs4_deviceid *);
>> -extern void nfs4_set_layout_deviceid(struct pnfs_layout_segment *,
>> +extern void nfs4_put_deviceid(struct nfs4_deviceid_cache *,
>>  				struct nfs4_deviceid *);
>> -extern void nfs4_put_unset_layout_deviceid(struct pnfs_layout_segment *,
>> -				struct nfs4_deviceid *,
>> -				void (*free_callback)(struct kref *));
>>  extern void nfs4_delete_device(struct nfs4_deviceid_cache *,
>>  				struct pnfs_deviceid *);
>>  
> 
> This doesn't look like it needs to be part of the initial single-layout
> submission. Why is it being labelled as a squashme?
> 
> Trond

No, this is a device_id cache per nfs-client it is part of the initial
getdeviceinfo call. Many "single-layout" may refer to the same device_id
therefor it is cached so the long getdeviceinfo call can be done only once.

Cheers
Boaz