2055da9738
So I've noticed a number of instances where it was not obvious from the
code whether ->task_list was for a wait-queue head or a wait-queue entry.
Furthermore, there's a number of wait-queue users where the lists are
not for 'tasks' but other entities (poll tables, etc.), in which case
the 'task_list' name is actively confusing.
To clear this all up, name the wait-queue head and entry list structure
fields unambiguously:
struct wait_queue_head::task_list => ::head
struct wait_queue_entry::task_list => ::entry
For example, this code:
rqw->wait.task_list.next != &wait->task_list
... is was pretty unclear (to me) what it's doing, while now it's written this way:
rqw->wait.head.next != &wait->entry
... which makes it pretty clear that we are iterating a list until we see the head.
Other examples are:
list_for_each_entry_safe(pos, next, &x->task_list, task_list) {
list_for_each_entry(wq, &fence->wait.task_list, task_list) {
... where it's unclear (to me) what we are iterating, and during review it's
hard to tell whether it's trying to walk a wait-queue entry (which would be
a bug), while now it's written as:
list_for_each_entry_safe(pos, next, &x->head, entry) {
list_for_each_entry(wq, &fence->wait.head, entry) {
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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_entry_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.entry)))
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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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