Commit b8f00e6b authored by Al Viro's avatar Al Viro
Browse files

acct: new lifetime rules 



Do not reuse bsd_acct_struct after closing the damn thing.
Structure lifetime is controlled by refcount now.  We also
have a mutex in there, held over closing and writing (the
file is O_APPEND, so we are not losing any concurrency).

As the result, we do not need to bother with get_file()/fput()
on log write anymore.  Moreover, do_acct_process() only needs
acct itself; file and pidns are picked from it.

Killed instances are distinguished by having NULL ->ns.
Refcount is protected by acct_lock; anybody taking the
mutex needs to grab a reference first.

The things will get a lot simpler in the next commits - this
is just the minimal chunk switching to the new lifetime rules.

Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 9df7fa16

kernel/acct.c

+114 −106
Original line number Diff line number Diff line
@@ -75,15 +75,11 @@ 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 {

	long			count;

	struct mutex		lock;

	int			active;

	unsigned long		needcheck;

	struct file		*file;
@@ -157,39 +153,59 @@ out: 
	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 acct_put(struct bsd_acct_struct *p)

{

	struct file *old_acct = NULL;

	struct pid_namespace *old_ns = NULL;

	spin_lock(&acct_lock);

	if (!--p->count)

		kfree(p);

	spin_unlock(&acct_lock);

}



	if (acct->file) {

		old_acct = acct->file;

		old_ns = acct->ns;

		acct->active = 0;

		acct->file = NULL;

		acct->ns = NULL;

		list_del(&acct->list);

static struct bsd_acct_struct *acct_get(struct bsd_acct_struct **p)

{

	struct bsd_acct_struct *res;

	spin_lock(&acct_lock);

again:

	res = *p;

	if (res)

		res->count++;

	spin_unlock(&acct_lock);

	if (res) {

		mutex_lock(&res->lock);

		if (!res->ns) {

			mutex_unlock(&res->lock);

			spin_lock(&acct_lock);

			if (!--res->count)

				kfree(res);

			goto again;

		}

	if (file) {

		acct->file = file;

		acct->ns = ns;

		acct->needcheck = jiffies;

		acct->active = 0;

		list_add(&acct->list, &acct_list);

	}

	if (old_acct) {

		mnt_unpin(old_acct->f_path.mnt);

	return res;

}



static void acct_kill(struct bsd_acct_struct *acct,

		      struct bsd_acct_struct *new)

{

	if (acct) {

		struct file *file = acct->file;

		struct pid_namespace *ns = acct->ns;

		spin_lock(&acct_lock);

		list_del(&acct->list);

		mnt_unpin(file->f_path.mnt);

		spin_unlock(&acct_lock);

		do_acct_process(acct, old_ns, old_acct);

		filp_close(old_acct, NULL);

		do_acct_process(acct);

		filp_close(file, NULL);

		spin_lock(&acct_lock);

		ns->bacct = new;

		if (new) {

			mnt_pin(new->file->f_path.mnt);

			list_add(&new->list, &acct_list);

		}

		acct->ns = NULL;

		mutex_unlock(&acct->lock);

		if (!(acct->count -= 2))

			kfree(acct);

		spin_unlock(&acct_lock);

	}

}
@@ -197,47 +213,50 @@ static int acct_on(struct filename *pathname) 
{

	struct file *file;

	struct vfsmount *mnt;

	struct pid_namespace *ns;

	struct bsd_acct_struct *acct = NULL;

	struct pid_namespace *ns = task_active_pid_ns(current);

	struct bsd_acct_struct *acct, *old;



	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;

		}

	}

	acct->count = 1;

	acct->file = file;

	acct->needcheck = jiffies;

	acct->ns = ns;

	mutex_init(&acct->lock);

	mnt = file->f_path.mnt;



	old = acct_get(&ns->bacct);

	if (old) {

		acct_kill(old, acct);

	} else {

		spin_lock(&acct_lock);

	if (ns->bacct == NULL) {

		ns->bacct = acct;

		acct = NULL;

	}



	mnt = file->f_path.mnt;

		mnt_pin(mnt);

	acct_file_reopen(ns->bacct, file, ns);

		list_add(&acct->list, &acct_list);

		spin_unlock(&acct_lock);



	}

	mntput(mnt); /* it's pinned, now give up active reference */

	kfree(acct);



	return 0;

}
@@ -270,15 +289,7 @@ SYSCALL_DEFINE1(acct, const char __user *, name) 
		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)->bacct), NULL);

	}



	return error;
@@ -298,8 +309,19 @@ void acct_auto_close_mnt(struct vfsmount *m) 
	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);

		if (acct->file->f_path.mnt == m) {

			acct->count++;

			spin_unlock(&acct_lock);

			mutex_lock(&acct->lock);

			if (!acct->ns) {

				mutex_unlock(&acct->lock);

				spin_lock(&acct_lock);

				if (!--acct->count)

					kfree(acct);

				goto restart;

			}

			acct_kill(acct, NULL);

			spin_lock(&acct_lock);

			goto restart;

		}

	spin_unlock(&acct_lock);
@@ -319,8 +341,19 @@ void acct_auto_close(struct super_block *sb) 
	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);

		if (acct->file->f_path.dentry->d_sb == sb) {

			acct->count++;

			spin_unlock(&acct_lock);

			mutex_lock(&acct->lock);

			if (!acct->ns) {

				mutex_unlock(&acct->lock);

				spin_lock(&acct_lock);

				if (!--acct->count)

					kfree(acct);

				goto restart;

			}

			acct_kill(acct, NULL);

			spin_lock(&acct_lock);

			goto restart;

		}

	spin_unlock(&acct_lock);
@@ -328,17 +361,7 @@ restart: 


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->bacct), NULL);

}



/*
@@ -507,12 +530,13 @@ static void fill_ac(acct_t *ac) 
/*

 *  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 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.
@@ -606,27 +630,12 @@ void acct_collect(long exitcode, int group_dead) 
static void slow_acct_process(struct pid_namespace *ns)

{

	for ( ; ns; ns = ns->parent) {

		struct file *file = NULL;

		struct bsd_acct_struct *acct;



		acct = ns->bacct;

		/*

		 * accelerate the common fastpath:

		 */

		if (!acct || !acct->file)

			continue;



		spin_lock(&acct_lock);

		file = acct->file;

		if (unlikely(!file)) {

			spin_unlock(&acct_lock);

			continue;

		struct bsd_acct_struct *acct = acct_get(&ns->bacct);

		if (acct) {

			do_acct_process(acct);

			mutex_unlock(&acct->lock);

			acct_put(acct);

		}

		get_file(file);

		spin_unlock(&acct_lock);



		do_acct_process(acct, ns, file);

		fput(file);

	}

}
@@ -645,8 +654,7 @@ void acct_process(void) 
	 * its parent.

	 */

	for (ns = task_active_pid_ns(current); ns != NULL; ns = ns->parent) {

		struct bsd_acct_struct *acct = ns->bacct;

		if (acct && acct->file)

		if (ns->bacct)

			break;

	}

	if (unlikely(ns))

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