1 files changed, 201 insertions, 255 deletions

diff --git a/kernel/acct.c b/kernel/acct.c
index 51793520566f..b4c667d22e79 100644
--- a/kernel/acct.c
+++ b/kernel/acct.c
@@ -59,6 +59,7 @@
 #include <asm/div64.h>
 #include <linux/blkdev.h> /* sector_div */
 #include <linux/pid_namespace.h>
+#include <linux/fs_pin.h>
 
 /*
  * These constants control the amount of freespace that suspend and
@@ -75,172 +76,190 @@ int acct_parm[3] = {4, 2, 30};
 /*
  * External references and all of the globals.
  */
-static void do_acct_process(struct bsd_acct_struct *acct,
-                struct pid_namespace *ns, struct file *);
+static void do_acct_process(struct bsd_acct_struct *acct);
 
-/*
- * 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 bsd_acct_struct {
+        struct fs_pin           pin;
+        struct mutex            lock;
         int                     active;
         unsigned long           needcheck;
         struct file             *file;
         struct pid_namespace    *ns;
-        struct list_head        list;
+        struct work_struct      work;
+        struct completion       done;
 };
 
-static DEFINE_SPINLOCK(acct_lock);
-static LIST_HEAD(acct_list);
-
 /*
  * Check the amount of free space and suspend/resume accordingly.
  */
-static int check_free_space(struct bsd_acct_struct *acct, struct file *file)
+static int check_free_space(struct bsd_acct_struct *acct)
 {
         struct kstatfs sbuf;
-        int res;
-        int act;
-        u64 resume;
-        u64 suspend;
-
-        spin_lock(&acct_lock);
-        res = acct->active;
-        if (!file || time_is_before_jiffies(acct->needcheck))
+
+        if (time_is_before_jiffies(acct->needcheck))
                 goto out;
-        spin_unlock(&acct_lock);
 
         /* May block */
-        if (vfs_statfs(&file->f_path, &sbuf))
-                return res;
-        suspend = sbuf.f_blocks * SUSPEND;
-        resume = sbuf.f_blocks * RESUME;
-
-        do_div(suspend, 100);
-        do_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->file under us we'ld better be
-         * silent and _not_ touch anything.
-         */
-        spin_lock(&acct_lock);
-        if (file != acct->file) {
-                if (act)
-                        res = act > 0;
+        if (vfs_statfs(&acct->file->f_path, &sbuf))
                 goto out;
-        }
 
         if (acct->active) {
-                if (act < 0) {
+                u64 suspend = sbuf.f_blocks * SUSPEND;
+                do_div(suspend, 100);
+                if (sbuf.f_bavail <= suspend) {
                         acct->active = 0;
                         pr_info("Process accounting paused\n");
                 }
         } else {
-                if (act > 0) {
+                u64 resume = sbuf.f_blocks * RESUME;
+                do_div(resume, 100);
+                if (sbuf.f_bavail >= resume) {
                         acct->active = 1;
                         pr_info("Process accounting resumed\n");
                 }
         }
 
         acct->needcheck = jiffies + ACCT_TIMEOUT*HZ;
-        res = acct->active;
 out:
-        spin_unlock(&acct_lock);
+        return acct->active;
+}
+
+static struct bsd_acct_struct *acct_get(struct pid_namespace *ns)
+{
+        struct bsd_acct_struct *res;
+again:
+        smp_rmb();
+        rcu_read_lock();
+        res = ACCESS_ONCE(ns->bacct);
+        if (!res) {
+                rcu_read_unlock();
+                return NULL;
+        }
+        if (!atomic_long_inc_not_zero(&res->pin.count)) {
+                rcu_read_unlock();
+                cpu_relax();
+                goto again;
+        }
+        rcu_read_unlock();
+        mutex_lock(&res->lock);
+        if (!res->ns) {
+                mutex_unlock(&res->lock);
+                pin_put(&res->pin);
+                goto again;
+        }
         return res;
 }
 
-/*
- * Close the old accounting file (if currently open) and then replace
- * it with file (if non-NULL).
- *
- * NOTE: acct_lock MUST be held on entry and exit.
- */
-static void acct_file_reopen(struct bsd_acct_struct *acct, struct file *file,
-                struct pid_namespace *ns)
+static void close_work(struct work_struct *work)
 {
-        struct file *old_acct = NULL;
-        struct pid_namespace *old_ns = NULL;
-
-        if (acct->file) {
-                old_acct = acct->file;
-                old_ns = acct->ns;
-                acct->active = 0;
-                acct->file = NULL;
+        struct bsd_acct_struct *acct = container_of(work, struct bsd_acct_struct, work);
+        struct file *file = acct->file;
+        if (file->f_op->flush)
+                file->f_op->flush(file, NULL);
+        __fput_sync(file);
+        complete(&acct->done);
+}
+
+static void acct_kill(struct bsd_acct_struct *acct,
+                      struct bsd_acct_struct *new)
+{
+        if (acct) {
+                struct pid_namespace *ns = acct->ns;
+                do_acct_process(acct);
+                INIT_WORK(&acct->work, close_work);
+                init_completion(&acct->done);
+                schedule_work(&acct->work);
+                wait_for_completion(&acct->done);
+                pin_remove(&acct->pin);
+                ns->bacct = new;
                 acct->ns = NULL;
-                list_del(&acct->list);
-        }
-        if (file) {
-                acct->file = file;
-                acct->ns = ns;
-                acct->needcheck = jiffies + ACCT_TIMEOUT*HZ;
-                acct->active = 1;
-                list_add(&acct->list, &acct_list);
+                atomic_long_dec(&acct->pin.count);
+                mutex_unlock(&acct->lock);
+                pin_put(&acct->pin);
         }
-        if (old_acct) {
-                mnt_unpin(old_acct->f_path.mnt);
-                spin_unlock(&acct_lock);
-                do_acct_process(acct, old_ns, old_acct);
-                filp_close(old_acct, NULL);
-                spin_lock(&acct_lock);
+}
+
+static void acct_pin_kill(struct fs_pin *pin)
+{
+        struct bsd_acct_struct *acct;
+        acct = container_of(pin, struct bsd_acct_struct, pin);
+        mutex_lock(&acct->lock);
+        if (!acct->ns) {
+                mutex_unlock(&acct->lock);
+                pin_put(pin);
+                acct = NULL;
         }
+        acct_kill(acct, NULL);
 }
 
 static int acct_on(struct filename *pathname)
 {
         struct file *file;
-        struct vfsmount *mnt;
-        struct pid_namespace *ns;
-        struct bsd_acct_struct *acct = NULL;
+        struct vfsmount *mnt, *internal;
+        struct pid_namespace *ns = task_active_pid_ns(current);
+        struct bsd_acct_struct *acct, *old;
+        int err;
+
+        acct = kzalloc(sizeof(struct bsd_acct_struct), GFP_KERNEL);
+        if (!acct)
+                return -ENOMEM;
 
         /* Difference from BSD - they don't do O_APPEND */
         file = file_open_name(pathname, O_WRONLY|O_APPEND|O_LARGEFILE, 0);
-        if (IS_ERR(file))
+        if (IS_ERR(file)) {
+                kfree(acct);
                 return PTR_ERR(file);
+        }
 
         if (!S_ISREG(file_inode(file)->i_mode)) {
+                kfree(acct);
                 filp_close(file, NULL);
                 return -EACCES;
         }
 
         if (!file->f_op->write) {
+                kfree(acct);
                 filp_close(file, NULL);
                 return -EIO;
         }
-
-        ns = task_active_pid_ns(current);
-        if (ns->bacct == NULL) {
-                acct = kzalloc(sizeof(struct bsd_acct_struct), GFP_KERNEL);
-                if (acct == NULL) {
-                        filp_close(file, NULL);
-                        return -ENOMEM;
-                }
+        internal = mnt_clone_internal(&file->f_path);
+        if (IS_ERR(internal)) {
+                kfree(acct);
+                filp_close(file, NULL);
+                return PTR_ERR(internal);
         }
-
-        spin_lock(&acct_lock);
-        if (ns->bacct == NULL) {
-                ns->bacct = acct;
-                acct = NULL;
+        err = mnt_want_write(internal);
+        if (err) {
+                mntput(internal);
+                kfree(acct);
+                filp_close(file, NULL);
+                return err;
         }
-
         mnt = file->f_path.mnt;
-        mnt_pin(mnt);
-        acct_file_reopen(ns->bacct, file, ns);
-        spin_unlock(&acct_lock);
-
-        mntput(mnt); /* it's pinned, now give up active reference */
-        kfree(acct);
-
+        file->f_path.mnt = internal;
+
+        atomic_long_set(&acct->pin.count, 1);
+        acct->pin.kill = acct_pin_kill;
+        acct->file = file;
+        acct->needcheck = jiffies;
+        acct->ns = ns;
+        mutex_init(&acct->lock);
+        mutex_lock_nested(&acct->lock, 1);      /* nobody has seen it yet */
+        pin_insert(&acct->pin, mnt);
+
+        old = acct_get(ns);
+        if (old)
+                acct_kill(old, acct);
+        else
+                ns->bacct = acct;
+        mutex_unlock(&acct->lock);
+        mnt_drop_write(mnt);
+        mntput(mnt);
         return 0;
 }
 
+static DEFINE_MUTEX(acct_on_mutex);
+
 /**
  * sys_acct - enable/disable process accounting
  * @name: file name for accounting records or NULL to shutdown accounting
@@ -264,78 +283,20 @@ SYSCALL_DEFINE1(acct, const char __user *, name)
 
                 if (IS_ERR(tmp))
                         return PTR_ERR(tmp);
+                mutex_lock(&acct_on_mutex);
                 error = acct_on(tmp);
+                mutex_unlock(&acct_on_mutex);
                 putname(tmp);
         } else {
-                struct bsd_acct_struct *acct;
-
-                acct = task_active_pid_ns(current)->bacct;
-                if (acct == NULL)
-                        return 0;
-
-                spin_lock(&acct_lock);
-                acct_file_reopen(acct, NULL, NULL);
-                spin_unlock(&acct_lock);
+                acct_kill(acct_get(task_active_pid_ns(current)), NULL);
         }
 
         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)
-{
-        struct bsd_acct_struct *acct;
-
-        spin_lock(&acct_lock);
-restart:
-        list_for_each_entry(acct, &acct_list, list)
-                if (acct->file && acct->file->f_path.mnt == m) {
-                        acct_file_reopen(acct, NULL, NULL);
-                        goto restart;
-                }
-        spin_unlock(&acct_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)
-{
-        struct bsd_acct_struct *acct;
-
-        spin_lock(&acct_lock);
-restart:
-        list_for_each_entry(acct, &acct_list, list)
-                if (acct->file && acct->file->f_path.dentry->d_sb == sb) {
-                        acct_file_reopen(acct, NULL, NULL);
-                        goto restart;
-                }
-        spin_unlock(&acct_lock);
-}
-
 void acct_exit_ns(struct pid_namespace *ns)
 {
-        struct bsd_acct_struct *acct = ns->bacct;
-
-        if (acct == NULL)
-                return;
-
-        spin_lock(&acct_lock);
-        if (acct->file != NULL)
-                acct_file_reopen(acct, NULL, NULL);
-        spin_unlock(&acct_lock);
-
-        kfree(acct);
+        acct_kill(acct_get(ns), NULL);
 }
 
 /*
@@ -450,38 +411,20 @@ static u32 encode_float(u64 value)
  *  do_exit() or when switching to a different output file.
  */
 
-/*
- *  do_acct_process does all actual work. Caller holds the reference to file.
- */
-static void do_acct_process(struct bsd_acct_struct *acct,
-                struct pid_namespace *ns, struct file *file)
+static void fill_ac(acct_t *ac)
 {
         struct pacct_struct *pacct = &current->signal->pacct;
-        acct_t ac;
-        mm_segment_t fs;
-        unsigned long flim;
         u64 elapsed, run_time;
         struct tty_struct *tty;
-        const struct cred *orig_cred;
-
-        /* Perform file operations on behalf of whoever enabled accounting */
-        orig_cred = override_creds(file->f_cred);
-
-        /*
-         * First check to see if there is enough free_space to continue
-         * the process accounting system.
-         */
-        if (!check_free_space(acct, file))
-                goto out;
 
         /*
          * Fill the accounting struct with the needed info as recorded
          * by the different kernel functions.
          */
-        memset(&ac, 0, sizeof(acct_t));
+        memset(ac, 0, sizeof(acct_t));
 
-        ac.ac_version = ACCT_VERSION | ACCT_BYTEORDER;
-        strlcpy(ac.ac_comm, current->comm, sizeof(ac.ac_comm));
+        ac->ac_version = ACCT_VERSION | ACCT_BYTEORDER;
+        strlcpy(ac->ac_comm, current->comm, sizeof(ac->ac_comm));
 
         /* calculate run_time in nsec*/
         run_time = ktime_get_ns();
@@ -489,9 +432,9 @@ static void do_acct_process(struct bsd_acct_struct *acct,
         /* convert nsec -> AHZ */
         elapsed = nsec_to_AHZ(run_time);
 #if ACCT_VERSION == 3
-        ac.ac_etime = encode_float(elapsed);
+        ac->ac_etime = encode_float(elapsed);
 #else
-        ac.ac_etime = encode_comp_t(elapsed < (unsigned long) -1l ?
+        ac->ac_etime = encode_comp_t(elapsed < (unsigned long) -1l ?
                                 (unsigned long) elapsed : (unsigned long) -1l);
 #endif
 #if ACCT_VERSION == 1 || ACCT_VERSION == 2
@@ -499,18 +442,58 @@ static void do_acct_process(struct bsd_acct_struct *acct,
                 /* new enlarged etime field */
                 comp2_t etime = encode_comp2_t(elapsed);
 
-                ac.ac_etime_hi = etime >> 16;
-                ac.ac_etime_lo = (u16) etime;
+                ac->ac_etime_hi = etime >> 16;
+                ac->ac_etime_lo = (u16) etime;
         }
 #endif
         do_div(elapsed, AHZ);
-        ac.ac_btime = get_seconds() - elapsed;
+        ac->ac_btime = get_seconds() - elapsed;
+#if ACCT_VERSION==2
+        ac->ac_ahz = AHZ;
+#endif
+
+        spin_lock_irq(&current->sighand->siglock);
+        tty = current->signal->tty;     /* Safe as we hold the siglock */
+        ac->ac_tty = tty ? old_encode_dev(tty_devnum(tty)) : 0;
+        ac->ac_utime = encode_comp_t(jiffies_to_AHZ(cputime_to_jiffies(pacct->ac_utime)));
+        ac->ac_stime = encode_comp_t(jiffies_to_AHZ(cputime_to_jiffies(pacct->ac_stime)));
+        ac->ac_flag = pacct->ac_flag;
+        ac->ac_mem = encode_comp_t(pacct->ac_mem);
+        ac->ac_minflt = encode_comp_t(pacct->ac_minflt);
+        ac->ac_majflt = encode_comp_t(pacct->ac_majflt);
+        ac->ac_exitcode = pacct->ac_exitcode;
+        spin_unlock_irq(&current->sighand->siglock);
+}
+/*
+ *  do_acct_process does all actual work. Caller holds the reference to file.
+ */
+static void do_acct_process(struct bsd_acct_struct *acct)
+{
+        acct_t ac;
+        unsigned long flim;
+        const struct cred *orig_cred;
+        struct pid_namespace *ns = acct->ns;
+        struct file *file = acct->file;
+
+        /*
+         * Accounting records are not subject to resource limits.
+         */
+        flim = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
+        current->signal->rlim[RLIMIT_FSIZE].rlim_cur = RLIM_INFINITY;
+        /* Perform file operations on behalf of whoever enabled accounting */
+        orig_cred = override_creds(file->f_cred);
+
+        /*
+         * First check to see if there is enough free_space to continue
+         * the process accounting system.
+         */
+        if (!check_free_space(acct))
+                goto out;
+
+        fill_ac(&ac);
         /* we really need to bite the bullet and change layout */
         ac.ac_uid = from_kuid_munged(file->f_cred->user_ns, orig_cred->uid);
         ac.ac_gid = from_kgid_munged(file->f_cred->user_ns, orig_cred->gid);
-#if ACCT_VERSION == 2
-        ac.ac_ahz = AHZ;
-#endif
 #if ACCT_VERSION == 1 || ACCT_VERSION == 2
         /* backward-compatible 16 bit fields */
         ac.ac_uid16 = ac.ac_uid;
@@ -522,45 +505,18 @@ static void do_acct_process(struct bsd_acct_struct *acct,
         ac.ac_ppid = task_tgid_nr_ns(rcu_dereference(current->real_parent), ns);
         rcu_read_unlock();
 #endif
-
-        spin_lock_irq(&current->sighand->siglock);
-        tty = current->signal->tty;     /* Safe as we hold the siglock */
-        ac.ac_tty = tty ? old_encode_dev(tty_devnum(tty)) : 0;
-        ac.ac_utime = encode_comp_t(jiffies_to_AHZ(cputime_to_jiffies(pacct->ac_utime)));
-        ac.ac_stime = encode_comp_t(jiffies_to_AHZ(cputime_to_jiffies(pacct->ac_stime)));
-        ac.ac_flag = pacct->ac_flag;
-        ac.ac_mem = encode_comp_t(pacct->ac_mem);
-        ac.ac_minflt = encode_comp_t(pacct->ac_minflt);
-        ac.ac_majflt = encode_comp_t(pacct->ac_majflt);
-        ac.ac_exitcode = pacct->ac_exitcode;
-        spin_unlock_irq(&current->sighand->siglock);
-        ac.ac_io = encode_comp_t(0 /* current->io_usage */);    /* %% */
-        ac.ac_rw = encode_comp_t(ac.ac_io / 1024);
-        ac.ac_swaps = encode_comp_t(0);
-
         /*
          * 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))
-                goto out;
-        /*
-         * Kernel segment override to datasegment and write it
-         * to the accounting file.
-         */
-        fs = get_fs();
-        set_fs(KERNEL_DS);
-        /*
-         * Accounting records are not subject to resource limits.
-         */
-        flim = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
-        current->signal->rlim[RLIMIT_FSIZE].rlim_cur = RLIM_INFINITY;
-        file->f_op->write(file, (char *)&ac,
-                               sizeof(acct_t), &file->f_pos);
-        current->signal->rlim[RLIMIT_FSIZE].rlim_cur = flim;
-        set_fs(fs);
-        file_end_write(file);
+        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);
 }
 
@@ -609,34 +565,20 @@ void acct_collect(long exitcode, int group_dead)
         spin_unlock_irq(&current->sighand->siglock);
 }
 
-static void acct_process_in_ns(struct pid_namespace *ns)
+static void slow_acct_process(struct pid_namespace *ns)
 {
-        struct file *file = NULL;
-        struct bsd_acct_struct *acct;
-
-        acct = ns->bacct;
-        /*
-         * accelerate the common fastpath:
-         */
-        if (!acct || !acct->file)
-                return;
-
-        spin_lock(&acct_lock);
-        file = acct->file;
-        if (unlikely(!file)) {
-                spin_unlock(&acct_lock);
-                return;
+        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);
+                }
         }
-        get_file(file);
-        spin_unlock(&acct_lock);
-
-        do_acct_process(acct, ns, file);
-        fput(file);
 }
 
 /**
- * acct_process - now just a wrapper around acct_process_in_ns,
- * which in turn is a wrapper around do_acct_process.
+ * acct_process
  *
  * handles process accounting for an exiting task
  */
@@ -649,6 +591,10 @@ void acct_process(void)
          * alive and holds its namespace, which in turn holds
          * its parent.
          */
-        for (ns = task_active_pid_ns(current); ns != NULL; ns = ns->parent)
-                acct_process_in_ns(ns);
+        for (ns = task_active_pid_ns(current); ns != NULL; ns = ns->parent) {
+                if (ns->bacct)
+                        break;
+        }
+        if (unlikely(ns))
+                slow_acct_process(ns);
 }