Re: [PATCH 4/7] NFSv4.1: trigger LAYOUTGET for writes

[Benny Halevy <bhalevy@panasas.com>]

On 2011-02-21 17:06, Fred Isaman wrote:
> 
> On Feb 21, 2011, at 10:49 AM, Benny Halevy wrote:
> 
>> On 2011-02-21 09:49, Fred Isaman wrote:
>>> Signed-off-by: Fred Isaman <iisaman@netapp.com>
>>> ---
>>> fs/nfs/pnfs.c  |   25 +++++++++++++++++++++++++
>>> fs/nfs/pnfs.h  |    7 +++++++
>>> fs/nfs/write.c |   32 ++++++++++++++++++++------------
>>> 3 files changed, 52 insertions(+), 12 deletions(-)
>>>
>>> diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
>>> index a7ea646..0ed3948d 100644
>>> --- a/fs/nfs/pnfs.c
>>> +++ b/fs/nfs/pnfs.c
>>> @@ -876,6 +876,31 @@ pnfs_pageio_init_read(struct nfs_pageio_descriptor *pgio, struct inode *inode)
>>> 	pgio->pg_test = (ld && ld->pg_test) ? pnfs_read_pg_test : NULL;
>>> }
>>>
>>> +static int pnfs_write_pg_test(struct nfs_pageio_descriptor *pgio,
>>> +			      struct nfs_page *prev,
>>> +			      struct nfs_page *req)
>>> +{
>>> +	if (pgio->pg_count == prev->wb_bytes) {
>>> +		/* This is first coelesce call for a series of nfs_pages */
>>> +		pgio->pg_lseg = pnfs_update_layout(pgio->pg_inode,
>>> +						   prev->wb_context,
>>> +						   IOMODE_RW);
>>> +	}
>>> +	return NFS_SERVER(pgio->pg_inode)->pnfs_curr_ld->pg_test(pgio, prev, req);
>>> +}
>>> +
>>> +/*
>>> + * rsize is already set by caller to MDS rsize.
>>> + */
>>
>> This comment is confusing and looks out of place...
> 
> OK.  I suggest we  remove similar comment in the read code too.
> 

Yeah.  Works for me.

>>
>>> +void
>>> +pnfs_pageio_init_write(struct nfs_pageio_descriptor *pgio, struct inode *inode)
>>> +{
>>> +	struct pnfs_layoutdriver_type *ld;
>>> +
>>> +	ld = NFS_SERVER(inode)->pnfs_curr_ld;
>>> +	pgio->pg_test = (ld && ld->pg_test) ? pnfs_write_pg_test : NULL;
>>> +}
>>> +
>>> /*
>>>  * Call the appropriate parallel I/O subsystem read function.
>>>  */
>>> diff --git a/fs/nfs/pnfs.h b/fs/nfs/pnfs.h
>>> index acbb778..1d4e631 100644
>>> --- a/fs/nfs/pnfs.h
>>> +++ b/fs/nfs/pnfs.h
>>> @@ -123,6 +123,7 @@ void unset_pnfs_layoutdriver(struct nfs_server *);
>>> enum pnfs_try_status pnfs_try_to_read_data(struct nfs_read_data *,
>>> 					    const struct rpc_call_ops *);
>>> void pnfs_pageio_init_read(struct nfs_pageio_descriptor *, struct inode *);
>>> +void pnfs_pageio_init_write(struct nfs_pageio_descriptor *, struct inode *);
>>> int pnfs_layout_process(struct nfs4_layoutget *lgp);
>>> void pnfs_free_lseg_list(struct list_head *tmp_list);
>>> void pnfs_destroy_layout(struct nfs_inode *);
>>> @@ -235,6 +236,12 @@ pnfs_pageio_init_read(struct nfs_pageio_descriptor *pgio, struct inode *ino)
>>> 	pgio->pg_test = NULL;
>>> }
>>>
>>> +static inline void
>>> +pnfs_pageio_init_write(struct nfs_pageio_descriptor *pgio, struct inode *ino)
>>> +{
>>> +	pgio->pg_test = NULL;
>>> +}
>>> +
>>> #endif /* CONFIG_NFS_V4_1 */
>>>
>>> #endif /* FS_NFS_PNFS_H */
>>> diff --git a/fs/nfs/write.c b/fs/nfs/write.c
>>> index 0df18ae..6cf5de6 100644
>>> --- a/fs/nfs/write.c
>>> +++ b/fs/nfs/write.c
>>> @@ -919,6 +919,8 @@ static int nfs_flush_multi(struct inode *inode, struct list_head *head, unsigned
>>> 	} while (nbytes != 0);
>>> 	atomic_set(&req->wb_complete, requests);
>>>
>>> +	/* We know lseg==NULL */
>>
>> Then maybe BUG_ON or WARN_ON(lseg != NULL)?
> 
> OK.
> 
> 
>>
>>> +	lseg = pnfs_update_layout(inode, req->wb_context, IOMODE_RW);
>>> 	ClearPageError(page);
>>> 	offset = 0;
>>> 	nbytes = count;
>>> @@ -940,6 +942,7 @@ static int nfs_flush_multi(struct inode *inode, struct list_head *head, unsigned
>>> 		nbytes -= wsize;
>>> 	} while (nbytes != 0);
>>>
>>> +	put_lseg(lseg);
>>> 	return ret;
>>>
>>> out_bad:
>>> @@ -965,11 +968,18 @@ static int nfs_flush_one(struct inode *inode, struct list_head *head, unsigned i
>>> 	struct nfs_page		*req;
>>> 	struct page		**pages;
>>> 	struct nfs_write_data	*data;
>>> +	int ret;
>>>
>>> 	data = nfs_writedata_alloc(npages);
>>> -	if (!data)
>>> -		goto out_bad;
>>> -
>>> +	if (!data) {
>>> +		while (!list_empty(head)) {
>>> +			req = nfs_list_entry(head->next);
>>
>> nit: it'd be cleaner to define a nfs_list_first_entry helper in nfs_page.h
>> rather than using a combination of list helpers and open code (head->next).
> 
> I would think that would be a separate patch. As this is just a simple move of pre-existing code,
> it is easier to see what is happening if I leave the copied code the same.
> 
> 

OK, makes sense.

Benny

>>
>>> +			nfs_list_remove_request(req);
>>> +			nfs_redirty_request(req);
>>> +		}
>>> +		ret = -ENOMEM;
>>> +		goto out;
>>> +	}
>>> 	pages = data->pagevec;
>>> 	while (!list_empty(head)) {
>>> 		req = nfs_list_entry(head->next);
>>> @@ -979,16 +989,14 @@ static int nfs_flush_one(struct inode *inode, struct list_head *head, unsigned i
>>> 		*pages++ = req->wb_page;
>>> 	}
>>> 	req = nfs_list_entry(data->pages.next);
>>> +	if ((!lseg) && list_is_singular(&data->pages))
>>> +		lseg = pnfs_update_layout(inode, req->wb_context, IOMODE_RW);
>>>
>>> 	/* Set up the argument struct */
>>> -	return nfs_write_rpcsetup(req, data, &nfs_write_full_ops, count, 0, lseg, how);
>>> - out_bad:
>>> -	while (!list_empty(head)) {
>>> -		req = nfs_list_entry(head->next);
>>> -		nfs_list_remove_request(req);
>>> -		nfs_redirty_request(req);
>>> -	}
>>> -	return -ENOMEM;
>>> +	ret = nfs_write_rpcsetup(req, data, &nfs_write_full_ops, count, 0, lseg, how);
>>> +out:
>>> +	put_lseg(lseg);
>>
>> Shouldn't you do that only if lseg was updated above?
>>
> 
> No, this is the put matching the get done in the pg_test function.  I'll comment that.
> 
> Fred
>