From: Trond Myklebust Date: Sat, 3 Sep 2016 14:39:51 +0000 (-0400) Subject: pNFS: Ensure LAYOUTGET and LAYOUTRETURN are properly serialised X-Git-Tag: v4.7.5~139 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f8421e38337f3b19d202932af1b1b37b515e5063;p=thirdparty%2Fkernel%2Fstable.git 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 --- diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c index 8b03cd3692792..229fa6139e0a3 100644 --- a/fs/nfs/pnfs.c +++ b/fs/nfs/pnfs.c @@ -876,6 +876,9 @@ void pnfs_clear_layoutreturn_waitbit(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;