Date: Tue, 19 Apr 2005 11:18:00 -0400 From: Brian Fundakowski Feldman <green@freebsd.org> To: Marc Olzheim <marcolz@stack.nl> Cc: freebsd-current@freebsd.org Subject: Re: NFS client/buffer cache deadlock Message-ID: <20050419151800.GE1157@green.homeunix.org> In-Reply-To: <20050419133227.GA11612@stack.nl> References: <20050415050821.GO981@green.homeunix.org> <20050415132108.GC85922@stack.nl> <20050415150708.GP981@green.homeunix.org> <20050418092550.GA97539@stack.nl> <20050418092752.GB97539@stack.nl> <20050418202213.GC1157@green.homeunix.org> <20050418203321.GA88774@stack.nl> <20050419133227.GA11612@stack.nl>
next in thread | previous in thread | raw e-mail | index | archive | help
On Tue, Apr 19, 2005 at 03:32:27PM +0200, Marc Olzheim wrote: > On Mon, Apr 18, 2005 at 10:33:21PM +0200, Marc Olzheim wrote: > > On Mon, Apr 18, 2005 at 04:22:13PM -0400, Brian Fundakowski Feldman wrote: > > > > > http://green.homeunix.org/~green/nfs_client.deadlock.patch > > > > Hmm, could you change it into a diff -u ? > > > > > > I replaced the patch with one with -u for you. > > > > Ok, great, I'll do some test on my -CURRENT machine at work > > in the morning (CEST). > > Hmm, sys/vnode.h has changed a lot from RELENG_5 to -CURRENT... Perhaps > someone with insight in this overhaul could change the patch to HEAD ? Does this work for you? cvs diff: Diffing sys Index: sys/buf.h =================================================================== RCS file: /usr/ncvs/src/sys/sys/buf.h,v retrieving revision 1.185 diff -u -r1.185 buf.h --- sys/buf.h 10 Feb 2005 12:17:48 -0000 1.185 +++ sys/buf.h 19 Apr 2005 14:30:54 -0000 @@ -465,6 +465,7 @@ extern int maxswzone; /* Max KVA for swap structures */ extern int maxbcache; /* Max KVA for buffer cache */ extern int runningbufspace; +extern int hibufspace; extern int buf_maxio; /* nominal maximum I/O for buffer */ extern struct buf *buf; /* The buffer headers. */ extern char *buffers; /* The buffer contents. */ cvs diff: Diffing kern Index: kern/vfs_bio.c =================================================================== RCS file: /usr/ncvs/src/sys/kern/vfs_bio.c,v retrieving revision 1.482 diff -u -r1.482 vfs_bio.c --- kern/vfs_bio.c 25 Mar 2005 00:20:37 -0000 1.482 +++ kern/vfs_bio.c 19 Apr 2005 14:30:54 -0000 @@ -127,7 +127,7 @@ static int lobufspace; SYSCTL_INT(_vfs, OID_AUTO, lobufspace, CTLFLAG_RD, &lobufspace, 0, "Minimum amount of buffers we want to have"); -static int hibufspace; +int hibufspace; SYSCTL_INT(_vfs, OID_AUTO, hibufspace, CTLFLAG_RD, &hibufspace, 0, "Maximum allowed value of bufspace (excluding buf_daemon)"); static int bufreusecnt; cvs diff: Diffing nfsclient Index: nfsclient/nfs_bio.c =================================================================== RCS file: /usr/ncvs/src/sys/nfsclient/nfs_bio.c,v retrieving revision 1.150 diff -u -r1.150 nfs_bio.c --- nfsclient/nfs_bio.c 18 Mar 2005 21:23:32 -0000 1.150 +++ nfsclient/nfs_bio.c 19 Apr 2005 15:11:13 -0000 @@ -844,6 +844,7 @@ struct vattr vattr; struct nfsmount *nmp = VFSTONFS(vp->v_mount); daddr_t lbn; + off_t commitleft; /* if non-zero, the amount left we may write */ int bcount; int n, on, error = 0; int haverslock = 0; @@ -873,6 +874,14 @@ */ if (ioflag & (IO_APPEND | IO_SYNC)) { if (np->n_flag & NMODIFIED) { +flush_and_restart: + /* + * Require non-blocking, synchronous writes to + * dirty files to inform the program it needs + * to fsync(2) explicitly. + */ + if (ioflag & IO_NDELAY) + return (EAGAIN); np->n_attrstamp = 0; error = nfs_vinvalbuf(vp, V_SAVE, td, 1); if (error) @@ -953,12 +962,65 @@ } biosize = vp->v_mount->mnt_stat.f_iosize; + commitleft = 0; + /* + * If there are possible modifications, find all of this file's + * B_NEEDCOMMIT buffers. If our writes would exceed the local + * maximum per-file write commit size when combined with those, + * we decide to flush and/or do a short write. + */ + if ((ioflag & (IO_SYNC | IO_INVAL)) != (IO_SYNC | IO_INVAL)) { + commitleft = nmp->nm_wcommitsize; + if (np->n_flag & NMODIFIED) { + int wouldcommit = 0; + BO_LOCK(vp->v_bufobj); + if (vp->v_bufobj.bo_dirty.bv_cnt != 0) { + TAILQ_FOREACH(bp, &vp->v_bufobj.bo_dirty.bv_hd, + b_bobufs) { + if (bp->b_flags & B_NEEDCOMMIT) + wouldcommit += bp->b_bcount; + } + } + BO_UNLOCK(vp->v_bufobj); + /* + * Since we're not operating synchronously and + * bypassing the buffer cache, we are in a commit + * and holding all of these buffers whether + * transmitted or not. If not limited, this + * will lead to the buffer cache deadlocking, + * as no one else can flush our uncommitted buffers. + */ + wouldcommit += uio->uio_resid; + /* + * If we would initially exceed the maximum + * outstanding write commit size, flush and restart. + */ + if (wouldcommit > commitleft) { + if (haverslock) { + nfs_rsunlock(np, td); + haverslock = 0; + } + goto flush_and_restart; + } + } else { + /* + * With no outstanding commits, we are limited only + * by commitleft as to how far we can go. + */ + } + } do { nfsstats.biocache_writes++; lbn = uio->uio_offset / biosize; on = uio->uio_offset & (biosize-1); n = min((unsigned)(biosize - on), uio->uio_resid); + /* Always allow at least the very first write. */ + if (commitleft > 0) { + commitleft -= n; + if (commitleft == 0) + commitleft = -1; + } again: /* * Handle direct append and file extension cases, calculate @@ -1146,10 +1208,21 @@ } else { bdwrite(bp); } - } while (uio->uio_resid > 0 && n > 0); + } while (uio->uio_resid > 0 && n > 0 && commitleft >= 0); - if (haverslock) + if (haverslock) { + haverslock = 0; nfs_rsunlock(np, td); + } + + /* + * On the off chance that we're trying to do a very large + * and non-atomic write, go ahead and let that just continue + * within the same call after flushing out what's been written. + */ + if (error == 0 && uio->uio_resid > 0 && n > 0 && commitleft < 0 && + !(ioflag & IO_UNIT)) + goto flush_and_restart; return (error); } Index: nfsclient/nfs_vfsops.c =================================================================== RCS file: /usr/ncvs/src/sys/nfsclient/nfs_vfsops.c,v retrieving revision 1.172 diff -u -r1.172 nfs_vfsops.c --- nfsclient/nfs_vfsops.c 24 Mar 2005 07:37:22 -0000 1.172 +++ nfsclient/nfs_vfsops.c 19 Apr 2005 14:32:19 -0000 @@ -41,6 +41,8 @@ #include <sys/param.h> #include <sys/systm.h> #include <sys/kernel.h> +#include <sys/bio.h> +#include <sys/buf.h> #include <sys/lock.h> #include <sys/malloc.h> #include <sys/mbuf.h> @@ -626,6 +628,12 @@ else nmp->nm_readahead = NFS_MAXRAHEAD; } + if ((argp->flags & NFSMNT_WCOMMITSIZE) && argp->wcommitsize >= 0) { + if (argp->wcommitsize < nmp->nm_wsize) + nmp->nm_wcommitsize = nmp->nm_wsize; + else + nmp->nm_wcommitsize = argp->wcommitsize; + } if ((argp->flags & NFSMNT_DEADTHRESH) && argp->deadthresh >= 0) { if (argp->deadthresh <= NFS_MAXDEADTHRESH) nmp->nm_deadthresh = argp->deadthresh; @@ -808,6 +816,7 @@ nmp->nm_wsize = NFS_WSIZE; nmp->nm_rsize = NFS_RSIZE; } + nmp->nm_wcommitsize = hibufspace / (desiredvnodes / 1000); nmp->nm_readdirsize = NFS_READDIRSIZE; nmp->nm_numgrps = NFS_MAXGRPS; nmp->nm_readahead = NFS_DEFRAHEAD; Index: nfsclient/nfsargs.h =================================================================== RCS file: /usr/ncvs/src/sys/nfsclient/nfsargs.h,v retrieving revision 1.67 diff -u -r1.67 nfsargs.h --- nfsclient/nfsargs.h 7 Jan 2005 01:45:51 -0000 1.67 +++ nfsclient/nfsargs.h 19 Apr 2005 14:30:54 -0000 @@ -56,7 +56,7 @@ int retrans; /* times to retry send */ int maxgrouplist; /* Max. size of group list */ int readahead; /* # of blocks to readahead */ - int __pad1; /* was "leaseterm" */ + int wcommitsize; /* Max. write commit size in bytes */ int deadthresh; /* Retrans threshold */ char *hostname; /* server's name */ int acregmin; /* cache attrs for reg files min time */ @@ -80,7 +80,7 @@ #define NFSMNT_NFSV3 0x00000200 /* Use NFS Version 3 protocol */ /* 0x400 free, was NFSMNT_KERB */ #define NFSMNT_DUMBTIMR 0x00000800 /* Don't estimate rtt dynamically */ -/* 0x1000 free, was NFSMNT_LEASETERM */ +#define NFSMNT_WCOMMITSIZE 0x00001000 /* set max write commit size */ #define NFSMNT_READAHEAD 0x00002000 /* set read ahead */ #define NFSMNT_DEADTHRESH 0x00004000 /* set dead server retry thresh */ #define NFSMNT_RESVPORT 0x00008000 /* Allocate a reserved port */ Index: nfsclient/nfsmount.h =================================================================== RCS file: /usr/ncvs/src/sys/nfsclient/nfsmount.h,v retrieving revision 1.29 diff -u -r1.29 nfsmount.h --- nfsclient/nfsmount.h 7 Jan 2005 01:45:51 -0000 1.29 +++ nfsclient/nfsmount.h 19 Apr 2005 14:30:54 -0000 @@ -74,6 +74,7 @@ int nm_wsize; /* Max size of write rpc */ int nm_readdirsize; /* Size of a readdir rpc */ int nm_readahead; /* Num. of blocks to readahead */ + int nm_wcommitsize; /* Max size of commit for write */ int nm_acdirmin; /* Directory attr cache min lifetime */ int nm_acdirmax; /* Directory attr cache max lifetime */ int nm_acregmin; /* Reg file attr cache min lifetime */ -- Brian Fundakowski Feldman \'[ FreeBSD ]''''''''''\ <> green@FreeBSD.org \ The Power to Serve! \ Opinions expressed are my own. \,,,,,,,,,,,,,,,,,,,,,,\
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20050419151800.GE1157>