On Tue, 2018-01-23 at 17:09 -0500, J. Bruce Fields wrote: > > The object still has useful information in it so we can't just > reinitalize it completely. I guess we could make nlm_get_host do > > if (refcount_read(&host->h_count)) > refcount_inc(&host->h_count); > else > refcount_set(&host->h_count, 1); > > Or we could just change the code so the refcount is always 1 higher > in > the NFS server case, so "1" instead of "0" is used to mean "nobody's > using this, you can garbage collect this", and then it won't go to 0 > until the garbage collector actually destroys it. > > This isn't an unusual pattern, what have other subsystems been doing? >
Hi Bruce, Sorry I forgot about the issues with the server garbage collector, and I applied these patches to my linux-next a couple of weeks ago. What say we fix the issue with something like the following? 8<------------------------------------------------------------ >From 83ce0f55ca54337a573f1d70038714815a9cd645 Mon Sep 17 00:00:00 2001 From: Trond Myklebust <[email protected]> Date: Tue, 23 Jan 2018 19:39:04 -0500 Subject: [PATCH] lockd: Fix server refcounting The server shouldn't actually delete the struct nlm_host until it hits the garbage collector. In order to make that work correctly with the refcount API, we can bump the refcount by one, and then use refcount_dec_if_one() in the garbage collector. Signed-off-by: Trond Myklebust <[email protected]> --- fs/lockd/host.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/fs/lockd/host.c b/fs/lockd/host.c index 7d6ab72bbe65..d35cd6be0675 100644 --- a/fs/lockd/host.c +++ b/fs/lockd/host.c @@ -388,6 +388,8 @@ struct nlm_host *nlmsvc_lookup_host(const struct svc_rqst *rqstp, ln->nrhosts++; nrhosts++; + refcount_inc(&host->h_count); + dprintk("lockd: %s created host %s (%s)\n", __func__, host->h_name, host->h_addrbuf); @@ -662,8 +664,7 @@ nlm_gc_hosts(struct net *net) for_each_host_safe(host, next, chain, nlm_server_hosts) { if (net && host->net != net) continue; - if (refcount_read(&host->h_count) || host->h_inuse - || time_before(jiffies, host->h_expires)) { + if (host->h_inuse || time_before(jiffies, host->h_expires)) { dprintk("nlm_gc_hosts skipping %s " "(cnt %d use %d exp %ld net %x)\n", host->h_name, refcount_read(&host->h_count), @@ -671,7 +672,8 @@ nlm_gc_hosts(struct net *net) host->net->ns.inum); continue; } - nlm_destroy_host_locked(host); + if (refcount_dec_if_one(&host->h_count)) + nlm_destroy_host_locked(host); } if (net) { -- 2.14.3 -- Trond Myklebust Linux NFS client maintainer, PrimaryData [email protected]
