Date: Mon, 10 Apr 2017 01:28:01 +0000 (UTC) From: Rick Macklem <rmacklem@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r316669 - head/sys/fs/nfsclient Message-ID: <201704100128.v3A1S1b2045657@repo.freebsd.org>
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Author: rmacklem Date: Mon Apr 10 01:28:01 2017 New Revision: 316669 URL: https://svnweb.freebsd.org/changeset/base/316669 Log: 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 Modified: head/sys/fs/nfsclient/nfs_clstate.c Modified: head/sys/fs/nfsclient/nfs_clstate.c ============================================================================== --- head/sys/fs/nfsclient/nfs_clstate.c Mon Apr 10 01:26:12 2017 (r316668) +++ head/sys/fs/nfsclient/nfs_clstate.c Mon Apr 10 01:28:01 2017 (r316669) @@ -797,8 +797,18 @@ nfscl_getcl(struct mount *mp, struct ucr (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
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