On Dec 22, 2010, at 5:00 PM, Trond Myklebust wrote:
> On Tue, 2010-12-21 at 23:00 -0500, Fred Isaman wrote:
>> A lsyout can request return-on-close. How this interacts with the
>> forgetful model of never sending LAYOUTRETURNS is a bit ambiguous.
>> We forget any layouts marked roc, and wait for them to be completely
>> forgotten before continuing with the close. In addition, to compensate
>> for races with any inflight LAYOUTGETs, and the fact that we do not get
>> any layout stateid back from the server, we set the barrier to the worst
>> case scenario of current_seqid + number of outstanding LAYOUTGETS.
>>
>> Signed-off-by: Fred Isaman <iisaman@xxxxxxxxxx>
>> ---
>> fs/nfs/inode.c | 1 +
>> fs/nfs/nfs4_fs.h | 2 +-
>> fs/nfs/nfs4proc.c | 21 +++++++++++-
>> fs/nfs/nfs4state.c | 7 +++-
>> fs/nfs/pnfs.c | 83 ++++++++++++++++++++++++++++++++++++++++++++++++
>> fs/nfs/pnfs.h | 28 ++++++++++++++++
>> include/linux/nfs_fs.h | 1 +
>> 7 files changed, 138 insertions(+), 5 deletions(-)
>>
>> diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
>> index 43a69da..c64bb40 100644
>> diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h
>> index 29d504d..90515de 100644
>> --- a/include/linux/nfs_fs.h
>> +++ b/include/linux/nfs_fs.h
>> @@ -190,6 +190,7 @@ struct nfs_inode {
>> struct rw_semaphore rwsem;
>>
>> /* pNFS layout information */
>> + struct rpc_wait_queue lo_rpcwaitq;
>> struct pnfs_layout_hdr *layout;
>> #endif /* CONFIG_NFS_V4*/
>> #ifdef CONFIG_NFS_FSCACHE
>
> I believe that I've asked this before. Why do we need a per-inode
> rpc_wait_queue just to support pnfs? That's a significant expansion of
> an already bloated structure.
>
> Can we please either make this a single per-filesystem wait queue, or
> else possibly a pool of wait queues?
>
> Trond
This was introduced to avoid deadlocks that were occurring when we had a single wait queue. However, the deadlocks I remember were due to a combination of the fact that, at the time, we handled EAGAIN errors of IO outside the RPC code, and we sent LAYOUTRETURN on such error. Since we do neither now, I believe a single per-filesystem wait queue will suffice. Anyone disagree?
Fred
>
> --
> Trond Myklebust
> Linux NFS client maintainer
>
> NetApp
> Trond.Myklebust@xxxxxxxxxx
> www.netapp.com
>
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