[PATCH 07/20] nfs: add a comment explaining the use of PG_private in the NFS client

[Peter Zijlstra <a.p.zijlstra@chello.nl>]

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Add a little comment explaining the use of PG_private in the NFS client.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
CC: Trond Myklebust <trond.myklebust@fys.uio.no>
---
 fs/nfs/write.c |    5 +++++
 1 file changed, 5 insertions(+)

Index: linux-2.6/fs/nfs/write.c
===================================================================
--- linux-2.6.orig/fs/nfs/write.c
+++ linux-2.6/fs/nfs/write.c
@@ -417,6 +417,11 @@ static int nfs_inode_add_request(struct 
 		if (nfs_have_delegation(inode, FMODE_WRITE))
 			nfsi->change_attr++;
 	}
+	/*
+	 * The PG_private bit is unfortunately needed if we want to fix the
+	 * hole in the mmap semantics. If we do not set it, then the VM will
+	 * fail to call the "releasepage" address ops.
+	 */
 	SetPagePrivate(req->wb_page);
 	nfsi->npages++;
 	atomic_inc(&req->wb_count);

--