From bf0291dd2267a2b9a4cd74d65249553d11bb45d6 Mon Sep 17 00:00:00 2001 From: Trond Myklebust Date: Sat, 3 Sep 2016 10:39:51 -0400 Subject: pNFS: Ensure LAYOUTGET and LAYOUTRETURN are properly serialised 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 Cc: stable@vger.kernel.org # v4.5+ Signed-off-by: Trond Myklebust --- fs/nfs/pnfs.c | 3 +++ 1 file changed, 3 insertions(+) (limited to 'fs') diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c index 6daf034645c8..519ad320f5cd 100644 --- a/fs/nfs/pnfs.c +++ b/fs/nfs/pnfs.c @@ -899,6 +899,9 @@ pnfs_prepare_layoutreturn(struct pnfs_layout_hdr *lo, nfs4_stateid *stateid, enum pnfs_iomode *iomode) { + /* 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; pnfs_get_layout_hdr(lo); -- cgit v1.2.3-58-ga151