From 8efffe80ba0d6efb892b42ee19d2313ac972c480 Mon Sep 17 00:00:00 2001 From: Rick Macklem Date: Mon, 10 Apr 2017 01:28:01 +0000 Subject: [PATCH] Avoid starvation of the server crash recovery thread for the NFSv4 client. This patch gives a requestor of the exclusive lock on the client state in the NFSv4 client priority over shared lock requestors. This avoids the server crash recovery thread being starved out by other threads doing RPCs. Tested by: cperciva PR: 216087 MFC after: 2 weeks --- sys/fs/nfsclient/nfs_clstate.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/sys/fs/nfsclient/nfs_clstate.c b/sys/fs/nfsclient/nfs_clstate.c index 5ae331151c72..4ec42b9f0db1 100644 --- a/sys/fs/nfsclient/nfs_clstate.c +++ b/sys/fs/nfsclient/nfs_clstate.c @@ -797,8 +797,18 @@ nfscl_getcl(struct mount *mp, struct ucred *cred, NFSPROC_T *p, (mp->mnt_kern_flag & MNTK_UNMOUNTF) == 0) igotlock = nfsv4_lock(&clp->nfsc_lock, 1, NULL, NFSCLSTATEMUTEXPTR, mp); - if (!igotlock) + if (igotlock == 0) { + /* + * Call nfsv4_lock() with "iwantlock == 0" so that it will + * wait for a pending exclusive lock request. This gives the + * exclusive lock request priority over this shared lock + * request. + * An exclusive lock on nfsc_lock is used mainly for server + * crash recoveries. + */ + nfsv4_lock(&clp->nfsc_lock, 0, NULL, NFSCLSTATEMUTEXPTR, mp); nfsv4_getref(&clp->nfsc_lock, NULL, NFSCLSTATEMUTEXPTR, mp); + } if (igotlock == 0 && (mp->mnt_kern_flag & MNTK_UNMOUNTF) != 0) { /* * Both nfsv4_lock() and nfsv4_getref() know to check