![Al Viro](/assets/img/avatar_default.png)
Add a new field to fs_pin - kill(pin). That's what umount and r/o remount will be calling for all pins attached to vfsmount and superblock resp. Called after bumping the refcount, so it won't go away under us. Dropping the refcount is responsibility of the instance. All generic stuff moved to fs/fs_pin.c; the next step will rip all the knowledge of kernel/acct.c from fs/super.c and fs/namespace.c. After that - death to mnt_pin(); it was intended to be usable as generic mechanism for code that wants to attach objects to vfsmount, so that they would not make the sucker busy and would get killed on umount. Never got it right; it remained acct.c-specific all along. Now it's very close to being killable. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
583 lines
15 KiB
C
583 lines
15 KiB
C
/*
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* linux/kernel/acct.c
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*
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* BSD Process Accounting for Linux
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*
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* Author: Marco van Wieringen <mvw@planets.elm.net>
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*
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* Some code based on ideas and code from:
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* Thomas K. Dyas <tdyas@eden.rutgers.edu>
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*
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* This file implements BSD-style process accounting. Whenever any
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* process exits, an accounting record of type "struct acct" is
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* written to the file specified with the acct() system call. It is
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* up to user-level programs to do useful things with the accounting
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* log. The kernel just provides the raw accounting information.
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*
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* (C) Copyright 1995 - 1997 Marco van Wieringen - ELM Consultancy B.V.
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*
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* Plugged two leaks. 1) It didn't return acct_file into the free_filps if
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* the file happened to be read-only. 2) If the accounting was suspended
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* due to the lack of space it happily allowed to reopen it and completely
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* lost the old acct_file. 3/10/98, Al Viro.
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*
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* Now we silently close acct_file on attempt to reopen. Cleaned sys_acct().
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* XTerms and EMACS are manifestations of pure evil. 21/10/98, AV.
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*
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* Fixed a nasty interaction with with sys_umount(). If the accointing
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* was suspeneded we failed to stop it on umount(). Messy.
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* Another one: remount to readonly didn't stop accounting.
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* Question: what should we do if we have CAP_SYS_ADMIN but not
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* CAP_SYS_PACCT? Current code does the following: umount returns -EBUSY
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* unless we are messing with the root. In that case we are getting a
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* real mess with do_remount_sb(). 9/11/98, AV.
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*
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* Fixed a bunch of races (and pair of leaks). Probably not the best way,
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* but this one obviously doesn't introduce deadlocks. Later. BTW, found
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* one race (and leak) in BSD implementation.
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* OK, that's better. ANOTHER race and leak in BSD variant. There always
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* is one more bug... 10/11/98, AV.
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*
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* Oh, fsck... Oopsable SMP race in do_process_acct() - we must hold
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* ->mmap_sem to walk the vma list of current->mm. Nasty, since it leaks
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* a struct file opened for write. Fixed. 2/6/2000, AV.
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*/
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#include <linux/mm.h>
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#include <linux/slab.h>
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#include <linux/acct.h>
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#include <linux/capability.h>
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#include <linux/file.h>
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#include <linux/tty.h>
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#include <linux/security.h>
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#include <linux/vfs.h>
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#include <linux/jiffies.h>
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#include <linux/times.h>
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#include <linux/syscalls.h>
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#include <linux/mount.h>
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#include <linux/uaccess.h>
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#include <asm/div64.h>
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#include <linux/blkdev.h> /* sector_div */
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#include <linux/pid_namespace.h>
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#include <linux/fs_pin.h>
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/*
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* These constants control the amount of freespace that suspend and
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* resume the process accounting system, and the time delay between
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* each check.
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* Turned into sysctl-controllable parameters. AV, 12/11/98
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*/
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int acct_parm[3] = {4, 2, 30};
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#define RESUME (acct_parm[0]) /* >foo% free space - resume */
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#define SUSPEND (acct_parm[1]) /* <foo% free space - suspend */
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#define ACCT_TIMEOUT (acct_parm[2]) /* foo second timeout between checks */
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/*
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* External references and all of the globals.
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*/
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static void do_acct_process(struct bsd_acct_struct *acct);
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struct bsd_acct_struct {
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struct fs_pin pin;
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struct mutex lock;
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int active;
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unsigned long needcheck;
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struct file *file;
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struct pid_namespace *ns;
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struct work_struct work;
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struct completion done;
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};
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/*
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* Check the amount of free space and suspend/resume accordingly.
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*/
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static int check_free_space(struct bsd_acct_struct *acct)
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{
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struct kstatfs sbuf;
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if (time_is_before_jiffies(acct->needcheck))
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goto out;
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/* May block */
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if (vfs_statfs(&acct->file->f_path, &sbuf))
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goto out;
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if (acct->active) {
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u64 suspend = sbuf.f_blocks * SUSPEND;
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do_div(suspend, 100);
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if (sbuf.f_bavail <= suspend) {
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acct->active = 0;
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printk(KERN_INFO "Process accounting paused\n");
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}
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} else {
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u64 resume = sbuf.f_blocks * RESUME;
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do_div(resume, 100);
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if (sbuf.f_bavail >= resume) {
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acct->active = 1;
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printk(KERN_INFO "Process accounting resumed\n");
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}
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}
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acct->needcheck = jiffies + ACCT_TIMEOUT*HZ;
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out:
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return acct->active;
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}
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static struct bsd_acct_struct *acct_get(struct pid_namespace *ns)
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{
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struct bsd_acct_struct *res;
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again:
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smp_rmb();
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rcu_read_lock();
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res = ACCESS_ONCE(ns->bacct);
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if (!res) {
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rcu_read_unlock();
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return NULL;
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}
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if (!atomic_long_inc_not_zero(&res->pin.count)) {
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rcu_read_unlock();
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cpu_relax();
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goto again;
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}
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rcu_read_unlock();
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mutex_lock(&res->lock);
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if (!res->ns) {
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mutex_unlock(&res->lock);
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pin_put(&res->pin);
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goto again;
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}
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return res;
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}
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static void close_work(struct work_struct *work)
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{
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struct bsd_acct_struct *acct = container_of(work, struct bsd_acct_struct, work);
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struct file *file = acct->file;
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mnt_unpin(file->f_path.mnt);
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if (file->f_op->flush)
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file->f_op->flush(file, NULL);
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__fput_sync(file);
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complete(&acct->done);
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}
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static void acct_kill(struct bsd_acct_struct *acct,
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struct bsd_acct_struct *new)
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{
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if (acct) {
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struct pid_namespace *ns = acct->ns;
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do_acct_process(acct);
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INIT_WORK(&acct->work, close_work);
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init_completion(&acct->done);
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schedule_work(&acct->work);
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wait_for_completion(&acct->done);
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pin_remove(&acct->pin);
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ns->bacct = new;
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acct->ns = NULL;
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atomic_long_dec(&acct->pin.count);
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mutex_unlock(&acct->lock);
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pin_put(&acct->pin);
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}
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}
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static void acct_pin_kill(struct fs_pin *pin)
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{
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struct bsd_acct_struct *acct;
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acct = container_of(pin, struct bsd_acct_struct, pin);
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mutex_lock(&acct->lock);
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if (!acct->ns) {
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mutex_unlock(&acct->lock);
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pin_put(pin);
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acct = NULL;
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}
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acct_kill(acct, NULL);
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}
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static int acct_on(struct filename *pathname)
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{
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struct file *file;
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struct vfsmount *mnt;
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struct pid_namespace *ns = task_active_pid_ns(current);
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struct bsd_acct_struct *acct, *old;
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acct = kzalloc(sizeof(struct bsd_acct_struct), GFP_KERNEL);
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if (!acct)
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return -ENOMEM;
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/* Difference from BSD - they don't do O_APPEND */
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file = file_open_name(pathname, O_WRONLY|O_APPEND|O_LARGEFILE, 0);
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if (IS_ERR(file)) {
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kfree(acct);
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return PTR_ERR(file);
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}
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if (!S_ISREG(file_inode(file)->i_mode)) {
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kfree(acct);
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filp_close(file, NULL);
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return -EACCES;
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}
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if (!file->f_op->write) {
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kfree(acct);
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filp_close(file, NULL);
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return -EIO;
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}
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atomic_long_set(&acct->pin.count, 1);
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acct->pin.kill = acct_pin_kill;
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acct->file = file;
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acct->needcheck = jiffies;
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acct->ns = ns;
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mutex_init(&acct->lock);
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mnt = file->f_path.mnt;
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mnt_pin(mnt);
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mutex_lock_nested(&acct->lock, 1); /* nobody has seen it yet */
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pin_insert(&acct->pin, mnt);
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old = acct_get(ns);
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if (old)
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acct_kill(old, acct);
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else
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ns->bacct = acct;
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mutex_unlock(&acct->lock);
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mntput(mnt); /* it's pinned, now give up active reference */
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return 0;
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}
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static DEFINE_MUTEX(acct_on_mutex);
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/**
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* sys_acct - enable/disable process accounting
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* @name: file name for accounting records or NULL to shutdown accounting
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*
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* Returns 0 for success or negative errno values for failure.
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*
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* sys_acct() is the only system call needed to implement process
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* accounting. It takes the name of the file where accounting records
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* should be written. If the filename is NULL, accounting will be
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* shutdown.
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*/
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SYSCALL_DEFINE1(acct, const char __user *, name)
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{
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int error = 0;
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if (!capable(CAP_SYS_PACCT))
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return -EPERM;
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if (name) {
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struct filename *tmp = getname(name);
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if (IS_ERR(tmp))
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return PTR_ERR(tmp);
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mutex_lock(&acct_on_mutex);
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error = acct_on(tmp);
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mutex_unlock(&acct_on_mutex);
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putname(tmp);
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} else {
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acct_kill(acct_get(task_active_pid_ns(current)), NULL);
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}
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return error;
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}
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void acct_exit_ns(struct pid_namespace *ns)
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{
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acct_kill(acct_get(ns), NULL);
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}
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/*
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* encode an unsigned long into a comp_t
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*
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* This routine has been adopted from the encode_comp_t() function in
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* the kern_acct.c file of the FreeBSD operating system. The encoding
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* is a 13-bit fraction with a 3-bit (base 8) exponent.
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*/
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#define MANTSIZE 13 /* 13 bit mantissa. */
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#define EXPSIZE 3 /* Base 8 (3 bit) exponent. */
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#define MAXFRACT ((1 << MANTSIZE) - 1) /* Maximum fractional value. */
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static comp_t encode_comp_t(unsigned long value)
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{
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int exp, rnd;
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exp = rnd = 0;
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while (value > MAXFRACT) {
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rnd = value & (1 << (EXPSIZE - 1)); /* Round up? */
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value >>= EXPSIZE; /* Base 8 exponent == 3 bit shift. */
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exp++;
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}
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/*
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* If we need to round up, do it (and handle overflow correctly).
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*/
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if (rnd && (++value > MAXFRACT)) {
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value >>= EXPSIZE;
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exp++;
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}
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/*
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* Clean it up and polish it off.
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*/
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exp <<= MANTSIZE; /* Shift the exponent into place */
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exp += value; /* and add on the mantissa. */
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return exp;
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}
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#if ACCT_VERSION==1 || ACCT_VERSION==2
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/*
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* encode an u64 into a comp2_t (24 bits)
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*
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* Format: 5 bit base 2 exponent, 20 bits mantissa.
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* The leading bit of the mantissa is not stored, but implied for
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* non-zero exponents.
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* Largest encodable value is 50 bits.
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*/
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#define MANTSIZE2 20 /* 20 bit mantissa. */
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#define EXPSIZE2 5 /* 5 bit base 2 exponent. */
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#define MAXFRACT2 ((1ul << MANTSIZE2) - 1) /* Maximum fractional value. */
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#define MAXEXP2 ((1 <<EXPSIZE2) - 1) /* Maximum exponent. */
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static comp2_t encode_comp2_t(u64 value)
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{
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int exp, rnd;
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exp = (value > (MAXFRACT2>>1));
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rnd = 0;
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while (value > MAXFRACT2) {
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rnd = value & 1;
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value >>= 1;
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exp++;
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}
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/*
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* If we need to round up, do it (and handle overflow correctly).
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*/
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if (rnd && (++value > MAXFRACT2)) {
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value >>= 1;
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exp++;
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}
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if (exp > MAXEXP2) {
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/* Overflow. Return largest representable number instead. */
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return (1ul << (MANTSIZE2+EXPSIZE2-1)) - 1;
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} else {
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return (value & (MAXFRACT2>>1)) | (exp << (MANTSIZE2-1));
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}
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}
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#endif
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#if ACCT_VERSION==3
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/*
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* encode an u64 into a 32 bit IEEE float
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*/
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static u32 encode_float(u64 value)
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{
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unsigned exp = 190;
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unsigned u;
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if (value==0) return 0;
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while ((s64)value > 0){
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value <<= 1;
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exp--;
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}
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u = (u32)(value >> 40) & 0x7fffffu;
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return u | (exp << 23);
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}
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#endif
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/*
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* Write an accounting entry for an exiting process
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*
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* The acct_process() call is the workhorse of the process
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* accounting system. The struct acct is built here and then written
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* into the accounting file. This function should only be called from
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* do_exit() or when switching to a different output file.
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*/
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static void fill_ac(acct_t *ac)
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{
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struct pacct_struct *pacct = ¤t->signal->pacct;
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u64 elapsed, run_time;
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struct tty_struct *tty;
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/*
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* Fill the accounting struct with the needed info as recorded
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* by the different kernel functions.
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*/
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memset(ac, 0, sizeof(acct_t));
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ac->ac_version = ACCT_VERSION | ACCT_BYTEORDER;
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strlcpy(ac->ac_comm, current->comm, sizeof(ac->ac_comm));
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/* calculate run_time in nsec*/
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run_time = ktime_get_ns();
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run_time -= current->group_leader->start_time;
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/* convert nsec -> AHZ */
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elapsed = nsec_to_AHZ(run_time);
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#if ACCT_VERSION==3
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ac->ac_etime = encode_float(elapsed);
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#else
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ac->ac_etime = encode_comp_t(elapsed < (unsigned long) -1l ?
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(unsigned long) elapsed : (unsigned long) -1l);
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#endif
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#if ACCT_VERSION==1 || ACCT_VERSION==2
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{
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/* new enlarged etime field */
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comp2_t etime = encode_comp2_t(elapsed);
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ac->ac_etime_hi = etime >> 16;
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ac->ac_etime_lo = (u16) etime;
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}
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#endif
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do_div(elapsed, AHZ);
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ac->ac_btime = get_seconds() - elapsed;
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#if ACCT_VERSION==2
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ac->ac_ahz = AHZ;
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#endif
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spin_lock_irq(¤t->sighand->siglock);
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tty = current->signal->tty; /* Safe as we hold the siglock */
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ac->ac_tty = tty ? old_encode_dev(tty_devnum(tty)) : 0;
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ac->ac_utime = encode_comp_t(jiffies_to_AHZ(cputime_to_jiffies(pacct->ac_utime)));
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ac->ac_stime = encode_comp_t(jiffies_to_AHZ(cputime_to_jiffies(pacct->ac_stime)));
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ac->ac_flag = pacct->ac_flag;
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ac->ac_mem = encode_comp_t(pacct->ac_mem);
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ac->ac_minflt = encode_comp_t(pacct->ac_minflt);
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ac->ac_majflt = encode_comp_t(pacct->ac_majflt);
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ac->ac_exitcode = pacct->ac_exitcode;
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spin_unlock_irq(¤t->sighand->siglock);
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}
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/*
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* do_acct_process does all actual work. Caller holds the reference to file.
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*/
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static void do_acct_process(struct bsd_acct_struct *acct)
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{
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acct_t ac;
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unsigned long flim;
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const struct cred *orig_cred;
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struct pid_namespace *ns = acct->ns;
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struct file *file = acct->file;
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/*
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* Accounting records are not subject to resource limits.
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*/
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flim = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
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current->signal->rlim[RLIMIT_FSIZE].rlim_cur = RLIM_INFINITY;
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/* Perform file operations on behalf of whoever enabled accounting */
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orig_cred = override_creds(file->f_cred);
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/*
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* First check to see if there is enough free_space to continue
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* the process accounting system.
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*/
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if (!check_free_space(acct))
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goto out;
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fill_ac(&ac);
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/* we really need to bite the bullet and change layout */
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ac.ac_uid = from_kuid_munged(file->f_cred->user_ns, orig_cred->uid);
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ac.ac_gid = from_kgid_munged(file->f_cred->user_ns, orig_cred->gid);
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#if ACCT_VERSION==1 || ACCT_VERSION==2
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/* backward-compatible 16 bit fields */
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ac.ac_uid16 = ac.ac_uid;
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ac.ac_gid16 = ac.ac_gid;
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#endif
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#if ACCT_VERSION==3
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ac.ac_pid = task_tgid_nr_ns(current, ns);
|
|
rcu_read_lock();
|
|
ac.ac_ppid = task_tgid_nr_ns(rcu_dereference(current->real_parent), ns);
|
|
rcu_read_unlock();
|
|
#endif
|
|
/*
|
|
* Get freeze protection. If the fs is frozen, just skip the write
|
|
* as we could deadlock the system otherwise.
|
|
*/
|
|
if (file_start_write_trylock(file)) {
|
|
/* it's been opened O_APPEND, so position is irrelevant */
|
|
loff_t pos = 0;
|
|
__kernel_write(file, (char *)&ac, sizeof(acct_t), &pos);
|
|
file_end_write(file);
|
|
}
|
|
out:
|
|
current->signal->rlim[RLIMIT_FSIZE].rlim_cur = flim;
|
|
revert_creds(orig_cred);
|
|
}
|
|
|
|
/**
|
|
* acct_collect - collect accounting information into pacct_struct
|
|
* @exitcode: task exit code
|
|
* @group_dead: not 0, if this thread is the last one in the process.
|
|
*/
|
|
void acct_collect(long exitcode, int group_dead)
|
|
{
|
|
struct pacct_struct *pacct = ¤t->signal->pacct;
|
|
cputime_t utime, stime;
|
|
unsigned long vsize = 0;
|
|
|
|
if (group_dead && current->mm) {
|
|
struct vm_area_struct *vma;
|
|
down_read(¤t->mm->mmap_sem);
|
|
vma = current->mm->mmap;
|
|
while (vma) {
|
|
vsize += vma->vm_end - vma->vm_start;
|
|
vma = vma->vm_next;
|
|
}
|
|
up_read(¤t->mm->mmap_sem);
|
|
}
|
|
|
|
spin_lock_irq(¤t->sighand->siglock);
|
|
if (group_dead)
|
|
pacct->ac_mem = vsize / 1024;
|
|
if (thread_group_leader(current)) {
|
|
pacct->ac_exitcode = exitcode;
|
|
if (current->flags & PF_FORKNOEXEC)
|
|
pacct->ac_flag |= AFORK;
|
|
}
|
|
if (current->flags & PF_SUPERPRIV)
|
|
pacct->ac_flag |= ASU;
|
|
if (current->flags & PF_DUMPCORE)
|
|
pacct->ac_flag |= ACORE;
|
|
if (current->flags & PF_SIGNALED)
|
|
pacct->ac_flag |= AXSIG;
|
|
task_cputime(current, &utime, &stime);
|
|
pacct->ac_utime += utime;
|
|
pacct->ac_stime += stime;
|
|
pacct->ac_minflt += current->min_flt;
|
|
pacct->ac_majflt += current->maj_flt;
|
|
spin_unlock_irq(¤t->sighand->siglock);
|
|
}
|
|
|
|
static void slow_acct_process(struct pid_namespace *ns)
|
|
{
|
|
for ( ; ns; ns = ns->parent) {
|
|
struct bsd_acct_struct *acct = acct_get(ns);
|
|
if (acct) {
|
|
do_acct_process(acct);
|
|
mutex_unlock(&acct->lock);
|
|
pin_put(&acct->pin);
|
|
}
|
|
}
|
|
}
|
|
|
|
/**
|
|
* acct_process
|
|
*
|
|
* handles process accounting for an exiting task
|
|
*/
|
|
void acct_process(void)
|
|
{
|
|
struct pid_namespace *ns;
|
|
|
|
/*
|
|
* This loop is safe lockless, since current is still
|
|
* alive and holds its namespace, which in turn holds
|
|
* its parent.
|
|
*/
|
|
for (ns = task_active_pid_ns(current); ns != NULL; ns = ns->parent) {
|
|
if (ns->bacct)
|
|
break;
|
|
}
|
|
if (unlikely(ns))
|
|
slow_acct_process(ns);
|
|
}
|