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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: Rik van Riel <riel@surriel.com> Reported-by: Chris Mason <clm@meta.com> Tested-by: Giuseppe Scrivano <gscrivan@redhat.com> Suggested-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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@ -1397,6 +1397,17 @@ struct vfsmount *mntget(struct vfsmount *mnt)
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}
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EXPORT_SYMBOL(mntget);
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/*
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* Make a mount point inaccessible to new lookups.
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* Because there may still be current users, the caller MUST WAIT
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* for an RCU grace period before destroying the mount point.
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*/
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void mnt_make_shortterm(struct vfsmount *mnt)
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{
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if (mnt)
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real_mount(mnt)->mnt_ns = NULL;
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}
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/**
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* path_is_mountpoint() - Check if path is a mount in the current namespace.
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* @path: path to check
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@ -4573,8 +4584,8 @@ EXPORT_SYMBOL_GPL(kern_mount);
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void kern_unmount(struct vfsmount *mnt)
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{
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/* release long term mount so mount point can be released */
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if (!IS_ERR_OR_NULL(mnt)) {
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real_mount(mnt)->mnt_ns = NULL;
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if (!IS_ERR(mnt)) {
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mnt_make_shortterm(mnt);
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synchronize_rcu(); /* yecchhh... */
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mntput(mnt);
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}
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@ -4586,8 +4597,7 @@ void kern_unmount_array(struct vfsmount *mnt[], unsigned int num)
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unsigned int i;
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for (i = 0; i < num; i++)
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if (mnt[i])
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real_mount(mnt[i])->mnt_ns = NULL;
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mnt_make_shortterm(mnt[i]);
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synchronize_rcu_expedited();
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for (i = 0; i < num; i++)
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mntput(mnt[i]);
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@ -88,6 +88,7 @@ extern void mnt_drop_write(struct vfsmount *mnt);
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extern void mnt_drop_write_file(struct file *file);
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extern void mntput(struct vfsmount *mnt);
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extern struct vfsmount *mntget(struct vfsmount *mnt);
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extern void mnt_make_shortterm(struct vfsmount *mnt);
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extern struct vfsmount *mnt_clone_internal(const struct path *path);
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extern bool __mnt_is_readonly(struct vfsmount *mnt);
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extern bool mnt_may_suid(struct vfsmount *mnt);
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@ -1709,11 +1709,6 @@ void mq_clear_sbinfo(struct ipc_namespace *ns)
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ns->mq_mnt->mnt_sb->s_fs_info = NULL;
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}
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void mq_put_mnt(struct ipc_namespace *ns)
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{
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kern_unmount(ns->mq_mnt);
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}
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static int __init init_mqueue_fs(void)
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{
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int error;
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@ -145,10 +145,11 @@ void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids,
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static void free_ipc_ns(struct ipc_namespace *ns)
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{
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/* mq_put_mnt() waits for a grace period as kern_unmount()
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* uses synchronize_rcu().
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/*
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* Caller needs to wait for an RCU grace period to have passed
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* after making the mount point inaccessible to new accesses.
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*/
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mq_put_mnt(ns);
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mntput(ns->mq_mnt);
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sem_exit_ns(ns);
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msg_exit_ns(ns);
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shm_exit_ns(ns);
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@ -168,6 +169,12 @@ static void free_ipc(struct work_struct *unused)
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struct llist_node *node = llist_del_all(&free_ipc_list);
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struct ipc_namespace *n, *t;
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llist_for_each_entry_safe(n, t, node, mnt_llist)
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mnt_make_shortterm(n->mq_mnt);
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/* Wait for any last users to have gone away. */
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synchronize_rcu();
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llist_for_each_entry_safe(n, t, node, mnt_llist)
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free_ipc_ns(n);
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}
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@ -56,10 +56,8 @@ struct pid_namespace;
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#ifdef CONFIG_POSIX_MQUEUE
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extern void mq_clear_sbinfo(struct ipc_namespace *ns);
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extern void mq_put_mnt(struct ipc_namespace *ns);
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#else
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static inline void mq_clear_sbinfo(struct ipc_namespace *ns) { }
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static inline void mq_put_mnt(struct ipc_namespace *ns) { }
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#endif
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#ifdef CONFIG_SYSVIPC
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