820f9f147d
This is needed to support lazily umounting locked mounts. Because the entire unmounted subtree needs to stay together until there are no users with references to any part of the subtree. To support this guarantee that the fs_pin m_list and s_list nodes are initialized by initializing them in init_fs_pin allowing for the possibility that pin_insert_group does not touch them. Further use hlist_del_init in pin_remove so that there is a hlist_unhashed test before the list we attempt to update the previous list item. Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
103 lines
2 KiB
C
103 lines
2 KiB
C
#include <linux/fs.h>
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#include <linux/sched.h>
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#include <linux/slab.h>
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#include "internal.h"
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#include "mount.h"
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static DEFINE_SPINLOCK(pin_lock);
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void pin_remove(struct fs_pin *pin)
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{
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spin_lock(&pin_lock);
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hlist_del_init(&pin->m_list);
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hlist_del_init(&pin->s_list);
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spin_unlock(&pin_lock);
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spin_lock_irq(&pin->wait.lock);
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pin->done = 1;
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wake_up_locked(&pin->wait);
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spin_unlock_irq(&pin->wait.lock);
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}
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void pin_insert_group(struct fs_pin *pin, struct vfsmount *m, struct hlist_head *p)
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{
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spin_lock(&pin_lock);
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if (p)
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hlist_add_head(&pin->s_list, p);
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hlist_add_head(&pin->m_list, &real_mount(m)->mnt_pins);
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spin_unlock(&pin_lock);
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}
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void pin_insert(struct fs_pin *pin, struct vfsmount *m)
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{
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pin_insert_group(pin, m, &m->mnt_sb->s_pins);
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}
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void pin_kill(struct fs_pin *p)
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{
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wait_queue_t wait;
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if (!p) {
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rcu_read_unlock();
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return;
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}
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init_wait(&wait);
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spin_lock_irq(&p->wait.lock);
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if (likely(!p->done)) {
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p->done = -1;
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spin_unlock_irq(&p->wait.lock);
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rcu_read_unlock();
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p->kill(p);
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return;
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}
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if (p->done > 0) {
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spin_unlock_irq(&p->wait.lock);
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rcu_read_unlock();
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return;
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}
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__add_wait_queue(&p->wait, &wait);
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while (1) {
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set_current_state(TASK_UNINTERRUPTIBLE);
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spin_unlock_irq(&p->wait.lock);
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rcu_read_unlock();
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schedule();
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rcu_read_lock();
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if (likely(list_empty(&wait.task_list)))
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break;
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/* OK, we know p couldn't have been freed yet */
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spin_lock_irq(&p->wait.lock);
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if (p->done > 0) {
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spin_unlock_irq(&p->wait.lock);
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break;
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}
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}
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rcu_read_unlock();
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}
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void mnt_pin_kill(struct mount *m)
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{
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while (1) {
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struct hlist_node *p;
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rcu_read_lock();
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p = ACCESS_ONCE(m->mnt_pins.first);
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if (!p) {
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rcu_read_unlock();
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break;
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}
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pin_kill(hlist_entry(p, struct fs_pin, m_list));
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}
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}
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void group_pin_kill(struct hlist_head *p)
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{
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while (1) {
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struct hlist_node *q;
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rcu_read_lock();
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q = ACCESS_ONCE(p->first);
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if (!q) {
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rcu_read_unlock();
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break;
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}
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pin_kill(hlist_entry(q, struct fs_pin, s_list));
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}
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}
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