Commit da27f796 authored by Rik van Riel's avatar Rik van Riel Committed by Al Viro
Browse files

ipc,namespace: batch free ipc_namespace structures 



Instead of waiting for an RCU grace period between each ipc_namespace
structure that is being freed, wait an RCU grace period for every batch
of ipc_namespace structures.

Thanks to Al Viro for the suggestion of the helper function.

This speeds up the run time of the test case that allocates ipc_namespaces
in a loop from 6 minutes, to a little over 1 second:

real	0m1.192s
user	0m0.038s
sys	0m1.152s

Signed-off-by: default avatarRik van Riel <riel@surriel.com>
Reported-by: default avatarChris Mason <clm@meta.com>
Tested-by: default avatarGiuseppe Scrivano <gscrivan@redhat.com>
Suggested-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent a80c4adc

fs/namespace.c

+14 −4
Original line number Original line Diff line number Diff line
@@ -1397,6 +1397,17 @@ struct vfsmount *mntget(struct vfsmount *mnt) 
}

}

EXPORT_SYMBOL(mntget);

EXPORT_SYMBOL(mntget);





/*

 * Make a mount point inaccessible to new lookups.

 * Because there may still be current users, the caller MUST WAIT

 * for an RCU grace period before destroying the mount point.

 */

void mnt_make_shortterm(struct vfsmount *mnt)

{

	if (mnt)

		real_mount(mnt)->mnt_ns = NULL;

}



/**

/**

 * path_is_mountpoint() - Check if path is a mount in the current namespace.

 * path_is_mountpoint() - Check if path is a mount in the current namespace.

 * @path: path to check

 * @path: path to check
@@ -4573,8 +4584,8 @@ EXPORT_SYMBOL_GPL(kern_mount); 
void kern_unmount(struct vfsmount *mnt)

void kern_unmount(struct vfsmount *mnt)

{

{

	/* release long term mount so mount point can be released */

	/* release long term mount so mount point can be released */

	if (!IS_ERR_OR_NULL(mnt)) {

	if (!IS_ERR(mnt)) {

		real_mount(mnt)->mnt_ns = NULL;

		mnt_make_shortterm(mnt);

		synchronize_rcu();	/* yecchhh... */

		synchronize_rcu();	/* yecchhh... */

		mntput(mnt);

		mntput(mnt);

	}

	}
@@ -4586,8 +4597,7 @@ void kern_unmount_array(struct vfsmount *mnt[], unsigned int num) 
	unsigned int i;

	unsigned int i;





	for (i = 0; i < num; i++)

	for (i = 0; i < num; i++)

		if (mnt[i])

		mnt_make_shortterm(mnt[i]);

			real_mount(mnt[i])->mnt_ns = NULL;

	synchronize_rcu_expedited();

	synchronize_rcu_expedited();

	for (i = 0; i < num; i++)

	for (i = 0; i < num; i++)

		mntput(mnt[i]);

		mntput(mnt[i]);

include/linux/mount.h

+1 −0
Original line number Original line Diff line number Diff line
@@ -88,6 +88,7 @@ extern void mnt_drop_write(struct vfsmount *mnt); 
extern void mnt_drop_write_file(struct file *file);

extern void mnt_drop_write_file(struct file *file);

extern void mntput(struct vfsmount *mnt);

extern void mntput(struct vfsmount *mnt);

extern struct vfsmount *mntget(struct vfsmount *mnt);

extern struct vfsmount *mntget(struct vfsmount *mnt);

extern void mnt_make_shortterm(struct vfsmount *mnt);

extern struct vfsmount *mnt_clone_internal(const struct path *path);

extern struct vfsmount *mnt_clone_internal(const struct path *path);

extern bool __mnt_is_readonly(struct vfsmount *mnt);

extern bool __mnt_is_readonly(struct vfsmount *mnt);

extern bool mnt_may_suid(struct vfsmount *mnt);

extern bool mnt_may_suid(struct vfsmount *mnt);

ipc/mqueue.c

+0 −5
Original line number Original line Diff line number Diff line
@@ -1709,11 +1709,6 @@ void mq_clear_sbinfo(struct ipc_namespace *ns) 
	ns->mq_mnt->mnt_sb->s_fs_info = NULL;

	ns->mq_mnt->mnt_sb->s_fs_info = NULL;

}

}





void mq_put_mnt(struct ipc_namespace *ns)

{

	kern_unmount(ns->mq_mnt);

}



static int __init init_mqueue_fs(void)

static int __init init_mqueue_fs(void)

{

{

	int error;

	int error;

ipc/namespace.c

+10 −3
Original line number Original line Diff line number Diff line
@@ -145,10 +145,11 @@ void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids, 




static void free_ipc_ns(struct ipc_namespace *ns)

static void free_ipc_ns(struct ipc_namespace *ns)

{

{

	/* mq_put_mnt() waits for a grace period as kern_unmount()

	/*

	 * uses synchronize_rcu().

	 * Caller needs to wait for an RCU grace period to have passed

	 * after making the mount point inaccessible to new accesses.

	 */

	 */

	mq_put_mnt(ns);

	mntput(ns->mq_mnt);

	sem_exit_ns(ns);

	sem_exit_ns(ns);

	msg_exit_ns(ns);

	msg_exit_ns(ns);

	shm_exit_ns(ns);

	shm_exit_ns(ns);
@@ -168,6 +169,12 @@ static void free_ipc(struct work_struct *unused) 
	struct llist_node *node = llist_del_all(&free_ipc_list);

	struct llist_node *node = llist_del_all(&free_ipc_list);

	struct ipc_namespace *n, *t;

	struct ipc_namespace *n, *t;





	llist_for_each_entry_safe(n, t, node, mnt_llist)

		mnt_make_shortterm(n->mq_mnt);



	/* Wait for any last users to have gone away. */

	synchronize_rcu();



	llist_for_each_entry_safe(n, t, node, mnt_llist)

	llist_for_each_entry_safe(n, t, node, mnt_llist)

		free_ipc_ns(n);

		free_ipc_ns(n);

}

}

ipc/util.h

+0 −2
Original line number Original line Diff line number Diff line
@@ -56,10 +56,8 @@ struct pid_namespace; 




#ifdef CONFIG_POSIX_MQUEUE

#ifdef CONFIG_POSIX_MQUEUE

extern void mq_clear_sbinfo(struct ipc_namespace *ns);

extern void mq_clear_sbinfo(struct ipc_namespace *ns);

extern void mq_put_mnt(struct ipc_namespace *ns);

#else

#else

static inline void mq_clear_sbinfo(struct ipc_namespace *ns) { }

static inline void mq_clear_sbinfo(struct ipc_namespace *ns) { }

static inline void mq_put_mnt(struct ipc_namespace *ns) { }

#endif

#endif





#ifdef CONFIG_SYSVIPC

#ifdef CONFIG_SYSVIPC