Re: [pnfs] [PATCH 1/2] pnfs: trim write count to wsize when retrying via MDS

[Benny Halevy <bhalevy@panasas.com>]

On 2011-01-20 07:20, Fred Isaman wrote:
> I'm going over the write code carefully preparing for wave4, and came
> across some code I traced to this patch.
> 
> Why is this needed?  Why doesn't the pg_bsize check in
> nfs_pageio_do_add_request() prevent this from ever being invoked?

Apparently this got squashed in too early.
It's actually needed only after
"pnfs: Introduce pnfs_call_done and io done callbacks"
which is post pnfs-submit.

Benny

> 
> Fred
> 
> On Sat, Feb 20, 2010 at 4:06 PM, Benny Halevy <bhalevy@panasas.com> wrote:
>> We coalesce pages based on the strip size that may be bigger
>> than the server can handle in one write (and even exceed the
>> maximum RPC message size on the server)
>>
>> Signed-off-by: Benny Halevy <bhalevy@panasas.com>
>> ---
>>  fs/nfs/nfs4proc.c       |    7 +++++++
>>  fs/nfs/write.c          |    8 ++++++++
>>  include/linux/nfs_xdr.h |    1 +
>>  3 files changed, 16 insertions(+), 0 deletions(-)
>>
>> diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
>> index 8132a96..93b1963 100644
>> --- a/fs/nfs/nfs4proc.c
>> +++ b/fs/nfs/nfs4proc.c
>> @@ -3180,6 +3180,13 @@ static int pnfs4_write_done(struct rpc_task *task, struct nfs_write_data *data)
>>        struct nfs_client *client = mds_svr->nfs_client;
>>        int status = task->tk_status >= 0 ? 0 : task->tk_status;
>>
>> +       /* restore original count after retry? */
>> +       if (data->pdata.orig_count) {
>> +               dprintk("%s: restoring original count %u\n", __func__,
>> +                       data->pdata.orig_count);
>> +               data->args.count = data->pdata.orig_count;
>> +       }
>> +
>>        if (data->pdata.pnfsflags & PNFS_NO_RPC)
>>                return 0;
>>
>> diff --git a/fs/nfs/write.c b/fs/nfs/write.c
>> index 90ce78e..fee6f00 100644
>> --- a/fs/nfs/write.c
>> +++ b/fs/nfs/write.c
>> @@ -1108,6 +1108,14 @@ void nfs_write_prepare(struct rpc_task *task, void *calldata)
>>  #ifdef CONFIG_PNFS
>>        if (data->fldata.ds_nfs_client)
>>                clp = data->fldata.ds_nfs_client;
>> +       else if (data->args.count > NFS_SERVER(data->inode)->wsize) {
>> +               /* retrying via MDS? */
>> +               data->pdata.orig_count = data->args.count;
>> +               data->args.count = NFS_SERVER(data->inode)->wsize;
>> +               dprintk("%s: trimmed count %u to wsize %u\n", __func__,
>> +                       data->pdata.orig_count, data->args.count);
>> +       } else
>> +               data->pdata.orig_count = 0;
>>  #endif /* CONFIG_PNFS */
>>
>>        if (nfs4_setup_sequence(clp, &data->args.seq_args,
>> diff --git a/include/linux/nfs_xdr.h b/include/linux/nfs_xdr.h
>> index efc4ca0..13ccd48 100644
>> --- a/include/linux/nfs_xdr.h
>> +++ b/include/linux/nfs_xdr.h
>> @@ -970,6 +970,7 @@ struct nfs_page;
>>  struct pnfs_call_data {
>>        struct pnfs_layout_segment *lseg;
>>        const struct rpc_call_ops *call_ops;
>> +       u32                     orig_count;     /* for retry via MDS */
>>        int                     pnfs_error;
>>        u8                      pnfsflags;
>>        u8                      how;            /* for FLUSH_STABLE */
>> --
>> 1.6.4.4
>>
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>>