[pnfs] [PATCH 02/28] pnfs: fix pnfs_{read|write}pages

[Fredric Isaman]

On Wed, 12 Mar 2008, Benny Halevy wrote:

>
> On Mar. 11, 2008, 21:31 +0200, Fred Isaman <iisaman at citi.umich.edu> wrote:
>> THIS WILL BREAK OTHER LAYOUT DRIVERS that rely on old behavior.
>
> Fred, do you have the cycles to fix the files and objects LDs
> for the new behavior so we can merge this patch onto the pnfs branch?
>

Yes, I'll work on that.

 	Fred

>>
>> This patch makes it possible to fall back to nfs from the layout driver's
>> read_pagelist or write_pagelist routines. It alters the call chain, and
>> expects ld_io_ops->{read|write}_pagelist to return either a 0 or 1,
>> consistent with its parents, putting any other information that needs to
>> be returned into the data.res and data.task structures.  The done routine
>> should be called by the layout driver if and only if it returns 0.
>>
>> Signed-off-by: Fred Isaman <iisaman at citi.umich.edu>
>> ---
>>  fs/nfs/pnfs.c             |   22 ++++++++++++----------
>>  include/linux/nfs4_pnfs.h |   16 ++++++++++++++--
>>  2 files changed, 26 insertions(+), 12 deletions(-)
>>
>> diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
>> index 8059181..7a7379d 100644
>> --- a/fs/nfs/pnfs.c
>> +++ b/fs/nfs/pnfs.c
>> @@ -1422,13 +1422,15 @@ pnfs_writepages(struct nfs_write_data *wdata, int how)
>>  							how,
>>  							wdata);
>>
>> -	if (status)
>> +	if (status) {
>
> a BUG_ON(status < 0) will be nice after all LDs are updated.
>
>>  		put_lseg(lseg);
>> -	if (status > 0) {
>> -		dprintk("%s: LD write_pagelist returned status %d > 0\n", __FUNCTION__, status);
>> -		pnfs_update_last_write(nfsi, args->offset, status);
>> +		wdata->pnfsflags &= ~PNFS_NO_RPC;
>> +	} else if (wdata->res.count > 0) {
>> +		/* Succesful synchronous case */
>> +		dprintk("%s: LD write_pagelist returned count %d > 0\n",
>> +			__func__, wdata->res.count);
>> +		pnfs_update_last_write(nfsi, args->offset, wdata->res.count);
>>  		pnfs_need_layoutcommit(nfsi, wdata->args.context);
>
> since the LD must call the done function also in the synchronous completion
> case, pnfs_update_last_write and pnfs_need_layoutcommit are called there.
>
>> -		status = 0;
>>  	}
>>
>>  out:
>> @@ -1503,12 +1505,12 @@ pnfs_readpages(struct nfs_read_data *rdata)
>>  							(loff_t)args->offset,
>>  							args->count,
>>  							rdata);
>> -	if (status)
>> +	if (status) {
>
> ditto BUG_ON(status < 0);
>
>>  		put_lseg(lseg);
>> -	if (status > 0) {
>> -		dprintk("%s: LD read_pagelist returned status %d > 0\n", __FUNCTION__, status);
>> -		status = 0;
>> -	}
>> +		rdata->pnfsflags &= ~PNFS_NO_RPC;
>> +	} else if (rdata->res.count > 0)
>> +		dprintk("%s: LD read_pagelist returned count %d > 0\n",
>> +			__func__, rdata->res.count);
>>
>>   out:
>>  	dprintk("%s: End Status %d\n", __FUNCTION__, status);
>> diff --git a/include/linux/nfs4_pnfs.h b/include/linux/nfs4_pnfs.h
>> index 381a599..2aaf526 100644
>> --- a/include/linux/nfs4_pnfs.h
>> +++ b/include/linux/nfs4_pnfs.h
>> @@ -116,8 +116,20 @@ struct layoutdriver_io_operations {
>>  	/* Functions that use the pagecache.
>>  	 * If use_pagecache == 1, then these functions must be implemented.
>>  	 */
>> -	ssize_t (*read_pagelist) (struct pnfs_layout_type *layoutid, struct page **pages, unsigned int pgbase, unsigned nr_pages, loff_t offset, size_t count, struct nfs_read_data *nfs_data);
>> -	ssize_t (*write_pagelist) (struct pnfs_layout_type *layoutid, struct page **pages, unsigned int pgbase, unsigned nr_pages, loff_t offset, size_t count, int sync, struct nfs_write_data *nfs_data);
>> +	/* read and write pagelist should return just 0 (to indicate
>> +	 * the layout code has taken control) or 1 (to indicate the
>> +	 * layoutcode wishes to fall back to normal nfs.)  If 0 is returned,
>> +	 * information can be passed back through nfs_data->res and
>> +	 * nfs_data->task.tk_status.
>
> "and the appropriate pnfs done function must be called (also when the I/O
> completes synchronously.)"
>
> Thanks,
>
> Benny
>
>> +	 */
>> +	int (*read_pagelist) (struct pnfs_layout_type *layoutid,
>> +			      struct page **pages, unsigned int pgbase,
>> +			      unsigned nr_pages, loff_t offset, size_t count,
>> +			      struct nfs_read_data *nfs_data);
>> +	int (*write_pagelist) (struct pnfs_layout_type *layoutid,
>> +			       struct page **pages, unsigned int pgbase,
>> +			       unsigned nr_pages, loff_t offset, size_t count,
>> +			       int sync, struct nfs_write_data *nfs_data);
>>  	int (*flush_one) (struct pnfs_layout_segment *, struct list_head *head, unsigned int npages, size_t count, int how);
>>  	void (*free_request_data) (struct nfs_page *);
>>
>
>