acct.c

linux 2.6.19 kernel source code before patching

/*
 *  linux/kernel/acct.c
 *
 *  BSD Process Accounting for Linux
 *
 *  Author: Marco van Wieringen <[e-mail]>
 *
 *  Some code based on ideas and code from:
 *  Thomas K. Dyas <[e-mail]>
 *
 *  This file implements BSD-style process accounting. Whenever any
 *  process exits, an accounting record of type "struct acct" is
 *  written to the file specified with the acct() system call. It is
 *  up to user-level programs to do useful things with the accounting
 *  log. The kernel just provides the raw accounting information.
 *
 * (C) Copyright 1995 - 1997 Marco van Wieringen - ELM Consultancy B.V.
 *
 *  Plugged two leaks. 1) It didn't return acct_file into the free_filps if
 *  the file happened to be read-only. 2) If the accounting was suspended
 *  due to the lack of space it happily allowed to reopen it and completely
 *  lost the old acct_file. 3/10/98, Al Viro.
 *
 *  Now we silently close acct_file on attempt to reopen. Cleaned sys_acct().
 *  XTerms and EMACS are manifestations of pure evil. 21/10/98, AV.
 *
 *  Fixed a nasty interaction with with sys_umount(). If the accointing
 *  was suspeneded we failed to stop it on umount(). Messy.
 *  Another one: remount to readonly didn't stop accounting.
 *	Question: what should we do if we have CAP_SYS_ADMIN but not
 *  CAP_SYS_PACCT? Current code does the following: umount returns -EBUSY
 *  unless we are messing with the root. In that case we are getting a
 *  real mess with do_remount_sb(). 9/11/98, AV.
 *
 *  Fixed a bunch of races (and pair of leaks). Probably not the best way,
 *  but this one obviously doesn't introduce deadlocks. Later. BTW, found
 *  one race (and leak) in BSD implementation.
 *  OK, that's better. ANOTHER race and leak in BSD variant. There always
 *  is one more bug... 10/11/98, AV.
 *
 *	Oh, fsck... Oopsable SMP race in do_process_acct() - we must hold
 * ->mmap_sem to walk the vma list of current->mm. Nasty, since it leaks
 * a struct file opened for write. Fixed. 2/6/2000, AV.
 */

#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/acct.h>
#include <linux/capability.h>
#include <linux/file.h>
#include <linux/tty.h>
#include <linux/security.h>
#include <linux/vfs.h>
#include <linux/jiffies.h>
#include <linux/times.h>
#include <linux/syscalls.h>
#include <linux/mount.h>
#include <asm/uaccess.h>
#include <asm/div64.h>
#include <linux/blkdev.h> /* sector_div */

/*
 * These constants control the amount of freespace that suspend and
 * resume the process accounting system, and the time delay between
 * each check.
 * Turned into sysctl-controllable parameters. AV, 12/11/98
 */

int acct_parm[3] = {4, 2, 30};
#define RESUME		(acct_parm[0])	/* >foo% free space - resume */
#define SUSPEND		(acct_parm[1])	/* <foo% free space - suspend */
#define ACCT_TIMEOUT	(acct_parm[2])	/* foo second timeout between checks */

/*
 * External references and all of the globals.
 */
static void do_acct_process(struct file *);

/*
 * This structure is used so that all the data protected by lock
 * can be placed in the same cache line as the lock.  This primes
 * the cache line to have the data after getting the lock.
 */
struct acct_glbs {
	spinlock_t		lock;
	volatile int		active;
	volatile int		needcheck;
	struct file		*file;
	struct timer_list	timer;
};

static struct acct_glbs acct_globals __cacheline_aligned =
	{__SPIN_LOCK_UNLOCKED(acct_globals.lock)};

/*
 * Called whenever the timer says to check the free space.
 */
static void acct_timeout(unsigned long unused)
{
	acct_globals.needcheck = 1;
}

/*
 * Check the amount of free space and suspend/resume accordingly.
 */
static int check_free_space(struct file *file)
{
	struct kstatfs sbuf;
	int res;
	int act;
	sector_t resume;
	sector_t suspend;

	spin_lock(&acct_globals.lock);
	res = acct_globals.active;
	if (!file || !acct_globals.needcheck)
		goto out;
	spin_unlock(&acct_globals.lock);

	/* May block */
	if (vfs_statfs(file->f_path.dentry, &sbuf))
		return res;
	suspend = sbuf.f_blocks * SUSPEND;
	resume = sbuf.f_blocks * RESUME;

	sector_div(suspend, 100);
	sector_div(resume, 100);

	if (sbuf.f_bavail <= suspend)
		act = -1;
	else if (sbuf.f_bavail >= resume)
		act = 1;
	else
		act = 0;

	/*
	 * If some joker switched acct_globals.file under us we'ld better be
	 * silent and _not_ touch anything.
	 */
	spin_lock(&acct_globals.lock);
	if (file != acct_globals.file) {
		if (act)
			res = act>0;
		goto out;
	}

	if (acct_globals.active) {
		if (act < 0) {
			acct_globals.active = 0;
			printk(KERN_INFO "Process accounting paused\n");
		}
	} else {
		if (act > 0) {
			acct_globals.active = 1;
			printk(KERN_INFO "Process accounting resumed\n");
		}
	}

	del_timer(&acct_globals.timer);
	acct_globals.needcheck = 0;
	acct_globals.timer.expires = jiffies + ACCT_TIMEOUT*HZ;
	add_timer(&acct_globals.timer);
	res = acct_globals.active;
out:
	spin_unlock(&acct_globals.lock);
	return res;
}

/*
 * Close the old accounting file (if currently open) and then replace
 * it with file (if non-NULL).
 *
 * NOTE: acct_globals.lock MUST be held on entry and exit.
 */
static void acct_file_reopen(struct file *file)
{
	struct file *old_acct = NULL;

	if (acct_globals.file) {
		old_acct = acct_globals.file;
		del_timer(&acct_globals.timer);
		acct_globals.active = 0;
		acct_globals.needcheck = 0;
		acct_globals.file = NULL;
	}
	if (file) {
		acct_globals.file = file;
		acct_globals.needcheck = 0;
		acct_globals.active = 1;
		/* It's been deleted if it was used before so this is safe */
		init_timer(&acct_globals.timer);
		acct_globals.timer.function = acct_timeout;
		acct_globals.timer.expires = jiffies + ACCT_TIMEOUT*HZ;
		add_timer(&acct_globals.timer);
	}
	if (old_acct) {
		mnt_unpin(old_acct->f_path.mnt);
		spin_unlock(&acct_globals.lock);
		do_acct_process(old_acct);
		filp_close(old_acct, NULL);
		spin_lock(&acct_globals.lock);
	}
}

static int acct_on(char *name)
{
	struct file *file;
	int error;

	/* Difference from BSD - they don't do O_APPEND */
	file = filp_open(name, O_WRONLY|O_APPEND|O_LARGEFILE, 0);
	if (IS_ERR(file))
		return PTR_ERR(file);

	if (!S_ISREG(file->f_path.dentry->d_inode->i_mode)) {
		filp_close(file, NULL);
		return -EACCES;
	}

	if (!file->f_op->write) {
		filp_close(file, NULL);
		return -EIO;
	}

	error = security_acct(file);
	if (error) {
		filp_close(file, NULL);
		return error;
	}

	spin_lock(&acct_globals.lock);
	mnt_pin(file->f_path.mnt);
	acct_file_reopen(file);
	spin_unlock(&acct_globals.lock);

	mntput(file->f_path.mnt); /* it's pinned, now give up active reference */

	return 0;
}

/**
 * sys_acct - enable/disable process accounting
 * @name: file name for accounting records or NULL to shutdown accounting
 *
 * Returns 0 for success or negative errno values for failure.
 *
 * sys_acct() is the only system call needed to implement process
 * accounting. It takes the name of the file where accounting records
 * should be written. If the filename is NULL, accounting will be
 * shutdown.
 */
asmlinkage long sys_acct(const char __user *name)
{
	int error;

	if (!capable(CAP_SYS_PACCT))
		return -EPERM;

	if (name) {
		char *tmp = getname(name);
		if (IS_ERR(tmp))
			return (PTR_ERR(tmp));
		error = acct_on(tmp);
		putname(tmp);
	} else {
		error = security_acct(NULL);
		if (!error) {
			spin_lock(&acct_globals.lock);
			acct_file_reopen(NULL);
			spin_unlock(&acct_globals.lock);
		}
	}
	return error;
}

/**
 * acct_auto_close - turn off a filesystem's accounting if it is on
 * @m: vfsmount being shut down
 *
 * If the accounting is turned on for a file in the subtree pointed to
 * to by m, turn accounting off.  Done when m is about to die.
 */
void acct_auto_close_mnt(struct vfsmount *m)
{
	spin_lock(&acct_globals.lock);
	if (acct_globals.file && acct_globals.file->f_path.mnt == m)
		acct_file_reopen(NULL);
	spin_unlock(&acct_globals.lock);
}

/**
 * acct_auto_close - turn off a filesystem's accounting if it is on
 * @sb: super block for the filesystem
 *
 * If the accounting is turned on for a file in the filesystem pointed
 * to by sb, turn accounting off.
 */
void acct_auto_close(struct super_block *sb)
{
	spin_lock(&acct_globals.lock);