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Merge branch 'work.namespace' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

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Pull ipc namespace update from Al Viro:
 "Rik's patches reducing the amount of synchronize_rcu() triggered by
  ipc namespace destruction.

  I've some pending stuff reducing that on the normal umount side, but
  it's nowhere near ready and Rik's stuff shouldn't be held back due to
  conflicts - I'll just redo the parts of my series that stray into
  ipc/*"

* 'work.namespace' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  ipc,namespace: batch free ipc_namespace structures
  ipc,namespace: make ipc namespace allocation wait for pending free
This commit is contained in:
Linus Torvalds
2023-02-24 19:20:07 -08:00
parent 10cc5d483e da27f796a8
commit 3df88c6a17
5 changed files with 41 additions and 20 deletions
Download Patch File Download Diff File Expand all files Collapse all files

5
ipc/mqueue.c
View File

@@ -1709,11 +1709,6 @@ void mq_clear_sbinfo(struct ipc_namespace *ns)
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)
{
int error;

35
ipc/namespace.c
View File

@@ -19,6 +19,12 @@
#include "util.h"
/*
* The work queue is used to avoid the cost of synchronize_rcu in kern_unmount.
*/
static void free_ipc(struct work_struct *unused);
static DECLARE_WORK(free_ipc_work, free_ipc);
static struct ucounts *inc_ipc_namespaces(struct user_namespace *ns)
{
return inc_ucount(ns, current_euid(), UCOUNT_IPC_NAMESPACES);
@@ -37,9 +43,18 @@ static struct ipc_namespace *create_ipc_ns(struct user_namespace *user_ns,
int err;
err = -ENOSPC;
again:
ucounts = inc_ipc_namespaces(user_ns);
if (!ucounts)
if (!ucounts) {
/*
* IPC namespaces are freed asynchronously, by free_ipc_work.
* If frees were pending, flush_work will wait, and
* return true. Fail the allocation if no frees are pending.
*/
if (flush_work(&free_ipc_work))
goto again;
goto fail;
}
err = -ENOMEM;
ns = kzalloc(sizeof(struct ipc_namespace), GFP_KERNEL_ACCOUNT);
@@ -130,10 +145,11 @@ void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids,
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);
msg_exit_ns(ns);
shm_exit_ns(ns);
@@ -153,15 +169,16 @@ static void free_ipc(struct work_struct *unused)
struct llist_node *node = llist_del_all(&free_ipc_list);
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)
free_ipc_ns(n);
}
/*
* The work queue is used to avoid the cost of synchronize_rcu in kern_unmount.
*/
static DECLARE_WORK(free_ipc_work, free_ipc);
/*
* put_ipc_ns - drop a reference to an ipc namespace.
* @ns: the namespace to put

2
ipc/util.h
View File

@@ -56,10 +56,8 @@ struct pid_namespace;
#ifdef CONFIG_POSIX_MQUEUE
extern void mq_clear_sbinfo(struct ipc_namespace *ns);
extern void mq_put_mnt(struct ipc_namespace *ns);
#else
static inline void mq_clear_sbinfo(struct ipc_namespace *ns) { }
static inline void mq_put_mnt(struct ipc_namespace *ns) { }
#endif
#ifdef CONFIG_SYSVIPC