From owner-cvs-src@FreeBSD.ORG Fri Sep 30 03:27:12 2005 Return-Path: X-Original-To: cvs-src@FreeBSD.org Delivered-To: cvs-src@FreeBSD.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 49E0116A41F; Fri, 30 Sep 2005 03:27:12 +0000 (GMT) (envelope-from csjp@FreeBSD.org) Received: from freefall.freebsd.org (freefall.freebsd.org [216.136.204.21]) by mx1.FreeBSD.org (Postfix) with ESMTP id E876343D4C; Fri, 30 Sep 2005 03:27:11 +0000 (GMT) (envelope-from csjp@FreeBSD.org) Received: from freefall.freebsd.org (csjp@localhost [127.0.0.1]) by freefall.freebsd.org (8.13.3/8.13.3) with ESMTP id j8U3RBgZ054584; Fri, 30 Sep 2005 03:27:11 GMT (envelope-from csjp@freefall.freebsd.org) Received: (from csjp@localhost) by freefall.freebsd.org (8.13.3/8.13.1/Submit) id j8U3RBtH054583; Fri, 30 Sep 2005 03:27:11 GMT (envelope-from csjp) Date: Fri, 30 Sep 2005 03:27:11 +0000 From: "Christian S.J. Peron" To: Don Lewis Message-ID: <20050930032711.GA24607@freefall.freebsd.org> References: <200509300130.j8U1U2nb098515@repoman.freebsd.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200509300130.j8U1U2nb098515@repoman.freebsd.org> User-Agent: Mutt/1.4.2.1i Cc: cvs-src@FreeBSD.org, src-committers@FreeBSD.org, cvs-all@FreeBSD.org Subject: Re: cvs commit: src/sys/kern vfs_bio.c vfs_subr.c src/sys/sys buf.h proc.h src/sys/ufs/ffs ffs_snapshot.c X-BeenThere: cvs-src@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: CVS commit messages for the src tree List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 30 Sep 2005 03:27:12 -0000 Hooooorraay! On Fri, Sep 30, 2005 at 01:30:02AM +0000, Don Lewis wrote: > truckman 2005-09-30 01:30:01 UTC > > FreeBSD src repository > > Modified files: > sys/kern vfs_bio.c vfs_subr.c > sys/sys buf.h proc.h > sys/ufs/ffs ffs_snapshot.c > Log: > Un-staticize runningbufwakeup() and staticize updateproc. > > Add a new private thread flag to indicate that the thread should > not sleep if runningbufspace is too large. > > Set this flag on the bufdaemon and syncer threads so that they skip > the waitrunningbufspace() call in bufwrite() rather than than > checking the proc pointer vs. the known proc pointers for these two > threads. A way of preventing these threads from being starved for > I/O but still placing limits on their outstanding I/O would be > desirable. > > Set this flag in ffs_copyonwrite() to prevent bufwrite() calls from > blocking on the runningbufspace check while holding snaplk. This > prevents snaplk from being held for an arbitrarily long period of > time if runningbufspace is high and greatly reduces the contention > for snaplk. The disadvantage is that ffs_copyonwrite() can start > a large amount of I/O if there are a large number of snapshots, > which could cause a deadlock in other parts of the code. > > Call runningbufwakeup() in ffs_copyonwrite() to decrement runningbufspace > before attempting to grab snaplk so that I/O requests waiting on > snaplk are not counted in runningbufspace as being in-progress. > Increment runningbufspace again before actually launching the > original I/O request. > > Prior to the above two changes, the system could deadlock if enough > I/O requests were blocked by snaplk to prevent runningbufspace from > falling below lorunningspace and one of the bawrite() calls in > ffs_copyonwrite() blocked in waitrunningbufspace() while holding > snaplk. > > See > > Revision Changes Path > 1.495 +3 -3 src/sys/kern/vfs_bio.c > 1.648 +2 -1 src/sys/kern/vfs_subr.c > 1.190 +1 -0 src/sys/sys/buf.h > 1.436 +1 -1 src/sys/sys/proc.h > 1.104 +16 -4 src/sys/ufs/ffs/ffs_snapshot.c -- Christian S.J. Peron csjp@FreeBSD.ORG FreeBSD Committer FreeBSD Security Team