Re: [PATCH v2 1/3] pNFS: recoalesce when ld write pagelist fails

[Peng Tao <bergwolf@gmail.com>]

Hi, Boaz,

On Sat, Aug 27, 2011 at 10:43 AM, Boaz Harrosh <bharrosh@panasas.com> wrote:
> On 08/23/2011 07:45 AM, Peng Tao wrote:
>> Hi, Benny and Boaz,
>>
>> On Sat, Aug 13, 2011 at 9:00 AM, Peng Tao <bergwolf@gmail.com> wrote:
>>> For pnfs pagelist write failure, we need to pg_recoalesce and resend
>>> IO to mds.
>>>
>>> Signed-off-by: Peng Tao <peng_tao@emc.com>
>>> ---
>>>  fs/nfs/pnfs.c  |   20 +++++++-------------
>>>  fs/nfs/pnfs.h  |    2 +-
>>>  fs/nfs/write.c |   25 ++++++++++++++++++++++++-
>>>  3 files changed, 32 insertions(+), 15 deletions(-)
>>>
>>> diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
>>> index e550e88..ad0579a 100644
>>> --- a/fs/nfs/pnfs.c
>>> +++ b/fs/nfs/pnfs.c
>>> @@ -1168,23 +1168,17 @@ EXPORT_SYMBOL_GPL(pnfs_generic_pg_test);
>>>  /*
>>>  * Called by non rpc-based layout drivers
>>>  */
>>> -int
>>> -pnfs_ld_write_done(struct nfs_write_data *data)
>>> +void pnfs_ld_write_done(struct nfs_write_data *data)
>>>  {
>>> -       int status;
>>> -
>>> -       if (!data->pnfs_error) {
>>> +       if (likely(!data->pnfs_error)) {
>>>                pnfs_set_layoutcommit(data);
>>>                data->mds_ops->rpc_call_done(&data->task, data);
>>> -               data->mds_ops->rpc_release(data);
>>> -               return 0;
>>> +       } else {
>>> +               put_lseg(data->lseg);
>>> +               data->lseg = NULL;
>>> +               dprintk("pnfs write error = %d\n", data->pnfs_error);
>>>        }
>>> -
>>> -       dprintk("%s: pnfs_error=%d, retry via MDS\n", __func__,
>>> -               data->pnfs_error);
>>> -       status = nfs_initiate_write(data, NFS_CLIENT(data->inode),
>>> -                                   data->mds_ops, NFS_FILE_SYNC);
>>> -       return status ? : -EAGAIN;
>>> +       data->mds_ops->rpc_release(data);
>>>  }
>>>  EXPORT_SYMBOL_GPL(pnfs_ld_write_done);
>>>
>>> diff --git a/fs/nfs/pnfs.h b/fs/nfs/pnfs.h
>>> index 01cbfd5..0fb0a41 100644
>>> --- a/fs/nfs/pnfs.h
>>> +++ b/fs/nfs/pnfs.h
>>> @@ -200,7 +200,7 @@ void pnfs_set_layoutcommit(struct nfs_write_data *wdata);
>>>  void pnfs_cleanup_layoutcommit(struct nfs4_layoutcommit_data *data);
>>>  int pnfs_layoutcommit_inode(struct inode *inode, bool sync);
>>>  int _pnfs_return_layout(struct inode *);
>>> -int pnfs_ld_write_done(struct nfs_write_data *);
>>> +void pnfs_ld_write_done(struct nfs_write_data *);
>>>  int pnfs_ld_read_done(struct nfs_read_data *);
>>>  struct pnfs_layout_segment *pnfs_update_layout(struct inode *ino,
>>>                                               struct nfs_open_context *ctx,
>>> diff --git a/fs/nfs/write.c b/fs/nfs/write.c
>>> index b39b37f..26b8d90 100644
>>> --- a/fs/nfs/write.c
>>> +++ b/fs/nfs/write.c
>>> @@ -1165,7 +1165,13 @@ static void nfs_writeback_done_full(struct rpc_task *task, void *calldata)
>>>  static void nfs_writeback_release_full(void *calldata)
>>>  {
>>>        struct nfs_write_data   *data = calldata;
>>> -       int status = data->task.tk_status;
>>> +       int ret, status = data->task.tk_status;
>>> +       struct nfs_pageio_descriptor pgio;
>>> +
>>> +       if (data->pnfs_error) {
>>> +               nfs_pageio_init_write_mds(&pgio, data->inode, FLUSH_STABLE);
>>> +               pgio.pg_recoalesce = 1;
>>> +       }
>>>
>>>        /* Update attributes as result of writeback. */
>>>        while (!list_empty(&data->pages)) {
>>> @@ -1181,6 +1187,11 @@ static void nfs_writeback_release_full(void *calldata)
>>>                        req->wb_bytes,
>>>                        (long long)req_offset(req));
>>>
>>> +               if (data->pnfs_error) {
>>> +                       dprintk(", pnfs error = %d\n", data->pnfs_error);
>>> +                       goto next;
>>> +               }
>>> +
>>>                if (status < 0) {
>>>                        nfs_set_pageerror(page);
>>>                        nfs_context_set_write_error(req->wb_context, status);
>>> @@ -1200,7 +1211,19 @@ remove_request:
>>>        next:
>>>                nfs_clear_page_tag_locked(req);
>>>                nfs_end_page_writeback(page);
>>> +               if (data->pnfs_error) {
>>> +                       lock_page(page);
>>> +                       nfs_pageio_cond_complete(&pgio, page->index);
>>> +                       ret = nfs_page_async_flush(&pgio, page, 0);
>>> +                       if (ret) {
>>> +                               nfs_set_pageerror(page);
>> My only concern about the patch is here. If we fail at
>> nfs_page_async_flush(), is it enough to just call nfs_set_pageerror()
>> on the page? Do we need to redirty the page as well, and maybe some
>> other things?
>>
>
> Hum? That's a very good question. nfs_end_page_writeback above does
> an end_page_writeback(), which does test_clear_page_writeback().
> Now in nfs_page_async_flush() you are adding the page back to the nfs writeback
> queue. So the question is when does test_set_page_writeback() is called?
> If it is called as part of the re-issue of write by NFS then you are
> fine because you clear it here but it will be set later on. But if
> it was done on entry into the queue. At the original sight of the call to
> nfs_page_async_flush(). Then it will not be set again and it might confuse
> the VFS since we will be re-clearing a cleared bit.
nfs_set_page_tag_locked() and nfs_set_page_writeback() are called
inside nfs_page_async_flush(), so we need to call
nfs_clear_page_tag_locked() and nfs_end_page_writeback() before
invoking nfs_page_async_flush(). But I am not quite sure about how to
handle nfs_page_async_flush() failure properly here (e.g., OOM). If we
don't re-dirty the page, will it break NFS writeback assumptions?

Thanks,
Tao
>
> So in short we should investigate if nfs_clear_page_tag_locked() &&
> nfs_end_page_writeback() sould only be called at the *else* clause
> of the "if (unlikely(data->pnfs_error))" above.
>
> I'll be testing this next week and we'll see.
>
> Trond do you know?
>
> Boaz
>
>
>> Thanks,
>> Tao
>>> +                               dprintk(", error = %d\n", ret);
>>> +                       }
>>> +                       unlock_page(page);
>>> +               }
>>>        }
>>> +       if (data->pnfs_error)
>>> +               nfs_pageio_complete(&pgio);
>>>        nfs_writedata_release(calldata);
>>>  }
>>>
>>> --
>>> 1.7.1.262.g5ef3d
>>>
>>>
>>
>>
>>
>
>