[PATCH] pnfs: call layoutcommit after flushing inode's data to disk.

[Boaz Harrosh <bharrosh@panasas.com>]

From: Tao Guo <guotao@nrchpc.ac.cn>

This is for a bug introduced to 2.6.34. In 2.6.32 and 2.6.33 we call
layoutcommit in nfs_sync_mapping_wait(), but in 2.6.34 we use
sync_inode() to sync inode's data, so the layoutcommit code is gone.

BTW: In current code, layoutcommit_ctx will increase refcount of
nfs_inode's ctx, so if layoutcommit_ctx is not NULL, we could not
reach nfs4_close_context ... --> __nfs_close().
So pnfs_layoutcommit_inode() in __nfs_close() will not be called in
whatever situation.
Why we have to use nfs_inode's ctx as layoutcommit_ctx, since we
only need its rpc_creds actually?

Boaz:
  Without this patch none-files layouts which return NFS_FILE_SYNC
  from writes, will eventually hang on uncommitted inodes.

  This patch reveals a bad design pattern from the pnfs-client. On
  none-files layouts nfs_post_op_update_inode_force_wcc or friends
  are never called and i_size_write() is never preformed on client.
  What happens is that the layoutcommit eventually updates the server.
  In Linux the sever would update i_size_attr and mtime. It would then
  be detected by the client and i_size is fetched from server. This is
  not nice client behaviour, and is not done so for files and none-pnfs
  IO. Sigh! 
  I think also files-lo might suffer from this in some cases, which means
  if commit is not preformed (It's just an hint) then writeout will have
  i_size  corruption.

Signed-off-by: Tao Guo <guotao@nrchpc.ac.cn>
Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>
---
 fs/nfs/write.c |    8 +++++++-
 1 files changed, 7 insertions(+), 1 deletions(-)

diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index dad8da3..9424203 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -1558,6 +1558,7 @@ int nfs_write_inode(struct inode *inode, struct writeback_control *wbc)
  */
 int nfs_wb_all(struct inode *inode)
 {
+	int ret;
 	struct writeback_control wbc = {
 		.sync_mode = WB_SYNC_ALL,
 		.nr_to_write = LONG_MAX,
@@ -1565,7 +1566,12 @@ int nfs_wb_all(struct inode *inode)
 		.range_end = LLONG_MAX,
 	};
 
-	return sync_inode(inode, &wbc);
+	ret = sync_inode(inode, &wbc);
+#ifdef CONFIG_NFS_V4_1
+	if (!ret && do_layoutcommit(NFS_I(inode)))
+		ret = pnfs_layoutcommit_inode(inode, 1);
+#endif
+	return ret;
 }
 
 int nfs_wb_page_cancel(struct inode *inode, struct page *page)
-- 
1.6.6.1