freebsd-skq/sys/kern/kern_acct.c
rwatson 257af099d1 Significant refactoring of the accounting code to improve locking and VFS
happiness, as well as correct other bugs:

- Replace notion of current and saved accounting credential/vnode with a
  single credential/vnode and an acct_suspended flag.  This simplifies the
  accounting logic substantially.

- Replace acct_mtx with acct_sx, a sleepable lock held exclusively during
  reconfiguration and space polling, but shared during log entry
  generation.  This avoids holding a mutex over sleepable VFS operations.

- Hold the sx lock over the duration of the I/O so that the vnode I/O
  cannot occur after vnode close, which could occur previously if
  accounting was disabled as a process exited.

- Write the accounting log entry with Giant conditionally acquired based
  on the file system where the log is stored.  Previously, the accounting
  code relied on the caller acquiring Giant.

- Acquire Giant conditionally in the accounting callout based on the file
  system where the accounting log is stored.  Run the callout MPSAFE.

- Expose acct_suspended via a read-only sysctl so it is possibly to
  programmatically determine whether accounting is suspended or not without
  attempting to parse logs.

- Check both acct_vp and acct_suspended lock-free before entering the
  accounting sx lock in acct().

- When accounting is disabled due to a VBAD vnode (i.e., forceable unmount),
  generate a log message indicating accounting has been disabled.

- Correct a long-standing bug in how free space is calculated and compared
  to the required space: generate and compare signed results, not unsigned
  results, or negative free space will cause accounting to not be suspended
  when required, or worse, incorrectly resumed once negative free space is
  reached.

MFC after:	2 weeks
2005-11-12 10:45:13 +00:00

423 lines
12 KiB
C

/*-
* Copyright (c) 1982, 1986, 1989, 1993
* The Regents of the University of California. All rights reserved.
* (c) UNIX System Laboratories, Inc.
* All or some portions of this file are derived from material licensed
* to the University of California by American Telephone and Telegraph
* Co. or Unix System Laboratories, Inc. and are reproduced herein with
* the permission of UNIX System Laboratories, Inc.
*
* Copyright (c) 1994 Christopher G. Demetriou
* Copyright (c) 2005 Robert N. M. Watson
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* @(#)kern_acct.c 8.1 (Berkeley) 6/14/93
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include "opt_mac.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/sysproto.h>
#include <sys/proc.h>
#include <sys/mac.h>
#include <sys/mount.h>
#include <sys/vnode.h>
#include <sys/fcntl.h>
#include <sys/syslog.h>
#include <sys/kernel.h>
#include <sys/sx.h>
#include <sys/sysent.h>
#include <sys/sysctl.h>
#include <sys/namei.h>
#include <sys/acct.h>
#include <sys/resourcevar.h>
#include <sys/tty.h>
/*
* The routines implemented in this file are described in:
* Leffler, et al.: The Design and Implementation of the 4.3BSD
* UNIX Operating System (Addison Welley, 1989)
* on pages 62-63.
*
* Arguably, to simplify accounting operations, this mechanism should
* be replaced by one in which an accounting log file (similar to /dev/klog)
* is read by a user process, etc. However, that has its own problems.
*/
/*
* Internal accounting functions.
* The former's operation is described in Leffler, et al., and the latter
* was provided by UCB with the 4.4BSD-Lite release
*/
static comp_t encode_comp_t(u_long, u_long);
static void acctwatch(void *);
/*
* Accounting callout used for periodic scheduling of acctwatch.
*/
static struct callout acctwatch_callout;
/*
* Accounting vnode pointer, saved vnode pointer, and flags for each.
* acct_sx protects against changes to the active vnode and credentials
* while accounting records are being committed to disk.
*/
static int acct_suspended;
static struct vnode *acct_vp;
static struct ucred *acct_cred;
static int acct_flags;
static struct sx acct_sx;
SX_SYSINIT(acct, &acct_sx, "acct_sx");
/*
* Values associated with enabling and disabling accounting
*/
static int acctsuspend = 2; /* stop accounting when < 2% free space left */
SYSCTL_INT(_kern, OID_AUTO, acct_suspend, CTLFLAG_RW,
&acctsuspend, 0, "percentage of free disk space below which accounting stops");
static int acctresume = 4; /* resume when free space risen to > 4% */
SYSCTL_INT(_kern, OID_AUTO, acct_resume, CTLFLAG_RW,
&acctresume, 0, "percentage of free disk space above which accounting resumes");
static int acctchkfreq = 15; /* frequency (in seconds) to check space */
SYSCTL_INT(_kern, OID_AUTO, acct_chkfreq, CTLFLAG_RW,
&acctchkfreq, 0, "frequency for checking the free space");
SYSCTL_INT(_kern, OID_AUTO, acct_suspended, CTLFLAG_RD, &acct_suspended, 0,
"Accounting suspended or not");
/*
* Accounting system call. Written based on the specification and
* previous implementation done by Mark Tinguely.
*
* MPSAFE
*/
int
acct(struct thread *td, struct acct_args *uap)
{
struct nameidata nd;
int error, flags;
/* Make sure that the caller is root. */
error = suser(td);
if (error)
return (error);
/*
* If accounting is to be started to a file, open that file for
* appending and make sure it's a 'normal'. While we could
* conditionally acquire Giant here, we're actually interacting with
* vnodes from possibly two file systems, making the logic a bit
* complicated. For now, use Giant unconditionally.
*/
mtx_lock(&Giant);
if (uap->path != NULL) {
NDINIT(&nd, LOOKUP, NOFOLLOW, UIO_USERSPACE, uap->path, td);
flags = FWRITE | O_APPEND;
error = vn_open(&nd, &flags, 0, -1);
if (error)
goto done;
NDFREE(&nd, NDF_ONLY_PNBUF);
#ifdef MAC
error = mac_check_system_acct(td->td_ucred, nd.ni_vp);
if (error) {
VOP_UNLOCK(nd.ni_vp, 0, td);
vn_close(nd.ni_vp, flags, td->td_ucred, td);
goto done;
}
#endif
VOP_UNLOCK(nd.ni_vp, 0, td);
if (nd.ni_vp->v_type != VREG) {
vn_close(nd.ni_vp, flags, td->td_ucred, td);
error = EACCES;
goto done;
}
#ifdef MAC
} else {
error = mac_check_system_acct(td->td_ucred, NULL);
if (error)
goto done;
#endif
}
/*
* Disallow concurrent access to the accounting vnode while we swap
* it out, in order to prevent access after close.
*/
sx_xlock(&acct_sx);
/*
* If accounting was previously enabled, kill the old space-watcher,
* close the file, and (if no new file was specified, leave). Reset
* the suspended state regardless of whether accounting remains
* enabled.
*/
acct_suspended = 0;
if (acct_vp != NULL) {
callout_stop(&acctwatch_callout);
error = vn_close(acct_vp, acct_flags, acct_cred, td);
crfree(acct_cred);
acct_vp = NULL;
acct_cred = NULL;
acct_flags = 0;
log(LOG_NOTICE, "Accounting disabled\n");
}
if (uap->path == NULL) {
sx_xunlock(&acct_sx);
goto done;
}
/*
* Save the new accounting file vnode, and schedule the new
* free space watcher.
*/
acct_vp = nd.ni_vp;
acct_cred = crhold(td->td_ucred);
acct_flags = flags;
callout_init(&acctwatch_callout, CALLOUT_MPSAFE);
sx_xunlock(&acct_sx);
log(LOG_NOTICE, "Accounting enabled\n");
acctwatch(NULL);
done:
mtx_unlock(&Giant);
return (error);
}
/*
* Write out process accounting information, on process exit.
* Data to be written out is specified in Leffler, et al.
* and are enumerated below. (They're also noted in the system
* "acct.h" header file.)
*/
int
acct_process(struct thread *td)
{
struct acct acct;
struct timeval ut, st, tmp;
struct plimit *newlim, *oldlim;
struct proc *p;
struct rusage *r;
int t, ret, vfslocked;
/*
* Lockless check of accounting condition before doing the hard
* work.
*/
if (acct_vp == NULL || acct_suspended)
return (0);
sx_slock(&acct_sx);
/*
* If accounting isn't enabled, don't bother. Have to check again
* once we own the lock in case we raced with disabling of accounting
* by another thread.
*/
if (acct_vp == NULL || acct_suspended) {
sx_sunlock(&acct_sx);
return (0);
}
p = td->td_proc;
/*
* Get process accounting information.
*/
PROC_LOCK(p);
/* (1) The name of the command that ran */
bcopy(p->p_comm, acct.ac_comm, sizeof acct.ac_comm);
/* (2) The amount of user and system time that was used */
calcru(p, &ut, &st);
acct.ac_utime = encode_comp_t(ut.tv_sec, ut.tv_usec);
acct.ac_stime = encode_comp_t(st.tv_sec, st.tv_usec);
/* (3) The elapsed time the command ran (and its starting time) */
tmp = boottime;
timevaladd(&tmp, &p->p_stats->p_start);
acct.ac_btime = tmp.tv_sec;
microuptime(&tmp);
timevalsub(&tmp, &p->p_stats->p_start);
acct.ac_etime = encode_comp_t(tmp.tv_sec, tmp.tv_usec);
/* (4) The average amount of memory used */
r = &p->p_stats->p_ru;
tmp = ut;
timevaladd(&tmp, &st);
t = tmp.tv_sec * hz + tmp.tv_usec / tick;
if (t)
acct.ac_mem = (r->ru_ixrss + r->ru_idrss + r->ru_isrss) / t;
else
acct.ac_mem = 0;
/* (5) The number of disk I/O operations done */
acct.ac_io = encode_comp_t(r->ru_inblock + r->ru_oublock, 0);
/* (6) The UID and GID of the process */
acct.ac_uid = p->p_ucred->cr_ruid;
acct.ac_gid = p->p_ucred->cr_rgid;
/* (7) The terminal from which the process was started */
SESS_LOCK(p->p_session);
if ((p->p_flag & P_CONTROLT) && p->p_pgrp->pg_session->s_ttyp)
acct.ac_tty = dev2udev(p->p_pgrp->pg_session->s_ttyp->t_dev);
else
acct.ac_tty = NODEV;
SESS_UNLOCK(p->p_session);
/* (8) The boolean flags that tell how the process terminated, etc. */
acct.ac_flag = p->p_acflag;
PROC_UNLOCK(p);
/*
* Eliminate any file size rlimit.
*/
newlim = lim_alloc();
PROC_LOCK(p);
oldlim = p->p_limit;
lim_copy(newlim, oldlim);
newlim->pl_rlimit[RLIMIT_FSIZE].rlim_cur = RLIM_INFINITY;
p->p_limit = newlim;
PROC_UNLOCK(p);
lim_free(oldlim);
/*
* Write the accounting information to the file.
*/
vfslocked = VFS_LOCK_GIANT(acct_vp->v_mount);
VOP_LEASE(acct_vp, td, acct_cred, LEASE_WRITE);
ret = vn_rdwr(UIO_WRITE, acct_vp, (caddr_t)&acct, sizeof (acct),
(off_t)0, UIO_SYSSPACE, IO_APPEND|IO_UNIT, acct_cred, NOCRED,
(int *)0, td);
VFS_UNLOCK_GIANT(vfslocked);
sx_sunlock(&acct_sx);
return (ret);
}
/*
* Encode_comp_t converts from ticks in seconds and microseconds
* to ticks in 1/AHZ seconds. The encoding is described in
* Leffler, et al., on page 63.
*/
#define MANTSIZE 13 /* 13 bit mantissa. */
#define EXPSIZE 3 /* Base 8 (3 bit) exponent. */
#define MAXFRACT ((1 << MANTSIZE) - 1) /* Maximum fractional value. */
static comp_t
encode_comp_t(u_long s, u_long us)
{
int exp, rnd;
exp = 0;
rnd = 0;
s *= AHZ;
s += us / (1000000 / AHZ); /* Maximize precision. */
while (s > MAXFRACT) {
rnd = s & (1 << (EXPSIZE - 1)); /* Round up? */
s >>= EXPSIZE; /* Base 8 exponent == 3 bit shift. */
exp++;
}
/* If we need to round up, do it (and handle overflow correctly). */
if (rnd && (++s > MAXFRACT)) {
s >>= EXPSIZE;
exp++;
}
/* Clean it up and polish it off. */
exp <<= MANTSIZE; /* Shift the exponent into place */
exp += s; /* and add on the mantissa. */
return (exp);
}
/*
* Periodically check the filesystem to see if accounting
* should be turned on or off. Beware the case where the vnode
* has been vgone()'d out from underneath us, e.g. when the file
* system containing the accounting file has been forcibly unmounted.
*/
/* ARGSUSED */
static void
acctwatch(void *a)
{
struct statfs sb;
int vfslocked;
sx_xlock(&acct_sx);
vfslocked = VFS_LOCK_GIANT(acct_vp->v_mount);
if (acct_vp->v_type == VBAD) {
(void) vn_close(acct_vp, acct_flags, acct_cred, NULL);
VFS_UNLOCK_GIANT(vfslocked);
crfree(acct_cred);
acct_vp = NULL;
acct_cred = NULL;
acct_flags = 0;
sx_xunlock(&acct_sx);
log(LOG_NOTICE, "Accounting disabled\n");
return;
}
/*
* Stopping here is better than continuing, maybe it will be VBAD
* next time around.
*/
if (VFS_STATFS(acct_vp->v_mount, &sb, curthread) < 0) {
VFS_UNLOCK_GIANT(vfslocked);
sx_xunlock(&acct_sx);
return;
}
VFS_UNLOCK_GIANT(vfslocked);
if (acct_suspended) {
if (sb.f_bavail > (int64_t)(acctresume * sb.f_blocks /
100)) {
acct_suspended = 0;
log(LOG_NOTICE, "Accounting resumed\n");
}
} else {
if (sb.f_bavail <= (int64_t)(acctsuspend * sb.f_blocks /
100)) {
acct_suspended = 1;
log(LOG_NOTICE, "Accounting suspended\n");
}
}
callout_reset(&acctwatch_callout, acctchkfreq * hz, acctwatch, NULL);
sx_xunlock(&acct_sx);
}