From 20e44c3acfa49a02645456047e9dc32274a6e559 Mon Sep 17 00:00:00 2001 From: Trond Myklebust Date: Sat, 3 Sep 2016 10:39:51 -0400 Subject: [PATCH] pNFS: Ensure LAYOUTGET and LAYOUTRETURN are properly serialised commit bf0291dd2267a2b9a4cd74d65249553d11bb45d6 upstream. According to RFC5661, the client is responsible for serialising LAYOUTGET and LAYOUTRETURN to avoid ambiguity. Consider the case where we send both in parallel. Client Server ====== ====== LAYOUTGET(seqid=X) LAYOUTRETURN(seqid=X) LAYOUTGET return seqid=X+1 LAYOUTRETURN return seqid=X+2 Process LAYOUTRETURN Forget layout stateid Process LAYOUTGET Set seqid=X+1 The client processes the layoutget/layoutreturn in the wrong order, and since the result of the layoutreturn was to clear the only existing layout segment, the client forgets the layout stateid. When the LAYOUTGET comes in, it is treated as having a completely new stateid, and so the client sets the wrong sequence id... Fix is to check if there are outstanding LAYOUTGET requests before we send the LAYOUTRETURN (note that LAYOUGET will already wait if it sees an outstanding LAYOUTRETURN). Signed-off-by: Trond Myklebust Signed-off-by: Trond Myklebust Signed-off-by: Greg Kroah-Hartman --- fs/nfs/pnfs.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c index ae340aca84c1..5cd3568eea06 100644 --- a/fs/nfs/pnfs.c +++ b/fs/nfs/pnfs.c @@ -365,6 +365,9 @@ pnfs_layout_need_return(struct pnfs_layout_hdr *lo, static bool pnfs_prepare_layoutreturn(struct pnfs_layout_hdr *lo) { + /* Serialise LAYOUTGET/LAYOUTRETURN */ + if (atomic_read(&lo->plh_outstanding) != 0) + return false; if (test_and_set_bit(NFS_LAYOUT_RETURN, &lo->plh_flags)) return false; lo->plh_return_iomode = 0; -- 2.34.1