NFS client/buffer cache deadlock
Brian Fundakowski Feldman
green at freebsd.org
Tue Apr 19 13:48:36 PDT 2005
On Tue, Apr 19, 2005 at 12:16:16PM -0400, Brian Fundakowski Feldman wrote:
> On Tue, Apr 19, 2005 at 06:09:00PM +0200, Marc Olzheim wrote:
> > On Tue, Apr 19, 2005 at 06:02:58PM +0200, Marc Olzheim wrote:
> > > On Tue, Apr 19, 2005 at 11:18:00AM -0400, Brian Fundakowski Feldman wrote:
> > > > Does this work for you?
> > >
> > > ...
> > >
> > > cc -c -O -pipe -Wall -Wredundant-decls -Wnested-externs -Wstrict-prototypes -Wmissing-prototypes -Wpointer-arith -Winline -Wcast-qual -fformat-extensions -std=c99 -g -nostdinc -I- -I. -I/usr/src/sys -I/usr/src/sys/contrib/dev/acpica -I/usr/src/sys/contrib/altq -I/usr/src/sys/contrib/ipfilter -I/usr/src/sys/contrib/pf -I/usr/src/sys/contrib/dev/ath -I/usr/src/sys/contrib/dev/ath/freebsd -I/usr/src/sys/contrib/ngatm -I/usr/src/sys/dev/twa -D_KERNEL -include opt_global.h -fno-common -finline-limit=8000 --param inline-unit-growth=100 --param large-function-growth=1000 -mno-align-long-strings -mpreferred-stack-boundary=2 -mno-mmx -mno-3dnow -mno-sse -mno-sse2 -ffreestanding -Werror /usr/src/sys/nfsclient/nfs_bio.c
> > > /usr/src/sys/nfsclient/nfs_bio.c: In function `nfs_write':
> > > /usr/src/sys/nfsclient/nfs_bio.c:976: error: invalid type argument of `->'
> > > /usr/src/sys/nfsclient/nfs_bio.c:976: error: invalid type argument of `->'
> > > /usr/src/sys/nfsclient/nfs_bio.c:984: error: invalid type argument of `->'
> > > /usr/src/sys/nfsclient/nfs_bio.c:984: error: invalid type argument of `->'
> > > *** Error code 1
> >
> > That's about the BO_LOCK(vp->v_bufobj); and the BO_UNLOCK(vp->v_bufobj);
>
> Yeah, I get that too. I have no clue why it's doing that, I was figuring
> it was just my compile setup...
Okay, stupid me. This compiles.
cvs diff: Diffing sys
Index: sys/buf.h
===================================================================
RCS file: /usr/ncvs/src/sys/sys/buf.h,v
retrieving revision 1.185
diff -u -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. */
Index: sys/bufobj.h
===================================================================
RCS file: /usr/ncvs/src/sys/sys/bufobj.h,v
retrieving revision 1.13
diff -u -u -r1.13 bufobj.h
--- sys/bufobj.h 19 Feb 2005 11:44:57 -0000 1.13
+++ sys/bufobj.h 19 Apr 2005 20:39:10 -0000
@@ -109,13 +109,13 @@
#define BO_LOCK(bo) \
do { \
- KASSERT (bo->bo_mtx != NULL, ("No lock in bufobj")); \
+ KASSERT((bo)->bo_mtx != NULL, ("No lock in bufobj")); \
mtx_lock((bo)->bo_mtx); \
} while (0)
#define BO_UNLOCK(bo) \
do { \
- KASSERT (bo->bo_mtx != NULL, ("No lock in bufobj")); \
+ KASSERT((bo)->bo_mtx != NULL, ("No lock in bufobj")); \
mtx_unlock((bo)->bo_mtx); \
} while (0)
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 -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 -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 20:38:34 -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 -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 -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 -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 at FreeBSD.org \ The Power to Serve! \
Opinions expressed are my own. \,,,,,,,,,,,,,,,,,,,,,,\
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