On Wed, Dec 18, 2019 at 06:20:56PM -0500, Chuck Lever wrote: > > On Dec 13, 2019, at 3:12 PM, Trond Myklebust <trondmy@xxxxxxxxxxxxxxx> wrote: > > Does something like the following help? > > > > 8<--------------------------------------------------- > > From caf515c82ed572e4f92ac8293e5da4818da0c6ce Mon Sep 17 00:00:00 2001 > > From: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx> > > Date: Fri, 13 Dec 2019 15:07:33 -0500 > > Subject: [PATCH] nfsd: Fix a soft lockup race in > > nfsd_file_mark_find_or_create() > > > > If nfsd_file_mark_find_or_create() keeps winning the race for the > > nfsd_file_fsnotify_group->mark_mutex against nfsd_file_mark_put() > > then it can soft lock up, since fsnotify_add_inode_mark() ends > > up always finding an existing entry. > > > > Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx> > > --- > > fs/nfsd/filecache.c | 8 ++++++-- > > 1 file changed, 6 insertions(+), 2 deletions(-) > > > > diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c > > index 9c2b29e07975..f275c11c4e28 100644 > > --- a/fs/nfsd/filecache.c > > +++ b/fs/nfsd/filecache.c > > @@ -132,9 +132,13 @@ nfsd_file_mark_find_or_create(struct nfsd_file *nf) > > struct nfsd_file_mark, > > nfm_mark)); > > mutex_unlock(&nfsd_file_fsnotify_group->mark_mutex); > > - fsnotify_put_mark(mark); > > - if (likely(nfm)) > > + if (nfm) { > > + fsnotify_put_mark(mark); > > break; > > + } > > + /* Avoid soft lockup race with nfsd_file_mark_put() */ > > + fsnotify_destroy_mark(mark, nfsd_file_fsnotify_group); > > + fsnotify_put_mark(mark); > > } else > > mutex_unlock(&nfsd_file_fsnotify_group->mark_mutex); > > > > I've tried to reproduce the lockup for three days with this patch > applied to my server. No lockup. > > Tested-by: Chuck Lever <chuck.lever@xxxxxxxxxx> I'm applying this for 5.5 with Chuck's tested-by and: Fixes: 65294c1f2c5e "nfsd: add a new struct file caching facility to nfsd" --b.