From 43d3be7a9e067acde2fccfb666c07526cc8ece02 Mon Sep 17 00:00:00 2001 From: Trond Myklebust Date: Mon, 26 Jul 2021 07:58:49 -0400 Subject: [PATCH] NFSv4/pNFS: Fix a layoutget livelock loop [ Upstream commit e20772cbdf463c12088837e5a08bde1b876bfd25 ] If NFS_LAYOUT_RETURN_REQUESTED is set, but there is no value set for the layout plh_return_seq, we can end up in a livelock loop in which every layout segment retrieved by a new call to layoutget is immediately invalidated by pnfs_layout_need_return(). To get around this, we should just set plh_return_seq to the current value of the layout stateid's seqid. Fixes: d474f96104bd ("NFS: Don't return layout segments that are in use") Signed-off-by: Trond Myklebust Signed-off-by: Anna Schumaker Signed-off-by: Sasha Levin --- fs/nfs/pnfs.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c index be960e47d7f61..3ee607aa007bf 100644 --- a/fs/nfs/pnfs.c +++ b/fs/nfs/pnfs.c @@ -347,11 +347,15 @@ pnfs_set_plh_return_info(struct pnfs_layout_hdr *lo, enum pnfs_iomode iomode, iomode = IOMODE_ANY; lo->plh_return_iomode = iomode; set_bit(NFS_LAYOUT_RETURN_REQUESTED, &lo->plh_flags); - if (seq != 0) { - WARN_ON_ONCE(lo->plh_return_seq != 0 && lo->plh_return_seq != seq); + /* + * We must set lo->plh_return_seq to avoid livelocks with + * pnfs_layout_need_return() + */ + if (seq == 0) + seq = be32_to_cpu(lo->plh_stateid.seqid); + if (!lo->plh_return_seq || pnfs_seqid_is_newer(seq, lo->plh_return_seq)) lo->plh_return_seq = seq; - pnfs_barrier_update(lo, seq); - } + pnfs_barrier_update(lo, seq); } static void