Add hashed waitqueue infrastructure to wait for ZONE_DEVICE pages to
drop their reference counts and be considered idle for DMA. This
facility will be used for filesystem callbacks / wakeups when DMA to a
DAX mapped range of a file ends.
For now, this implementation does not have functional behavior change
outside of waking waitqueues that do not have any waiters present.
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
---
drivers/dax/super.c | 1 +
include/linux/wait_bit.h | 10 +++++++
kernel/sched/wait_bit.c | 64 ++++++++++++++++++++++++++++++++++++++++------
3 files changed, 67 insertions(+), 8 deletions(-)
diff --git a/drivers/dax/super.c b/drivers/dax/super.c
index 4ac359e14777..a5a4b95ffdaf 100644
--- a/drivers/dax/super.c
+++ b/drivers/dax/super.c
@@ -167,6 +167,7 @@ struct dax_device {
#if IS_ENABLED(CONFIG_FS_DAX)
static void generic_dax_pagefree(struct page *page, void *data)
{
+ wake_up_devmap_idle(&page->_refcount);
}
struct dax_device *fs_dax_claim_bdev(struct block_device *bdev, void *owner)
diff --git a/include/linux/wait_bit.h b/include/linux/wait_bit.h
index 12b26660d7e9..6186ecdb9df7 100644
--- a/include/linux/wait_bit.h
+++ b/include/linux/wait_bit.h
@@ -30,10 +30,12 @@ int __wait_on_bit(struct wait_queue_head *wq_head, struct wait_bit_queue_entry *
int __wait_on_bit_lock(struct wait_queue_head *wq_head, struct wait_bit_queue_entry *wbq_entry, wait_bit_action_f *action, unsigned int mode);
void wake_up_bit(void *word, int bit);
void wake_up_atomic_t(atomic_t *p);
+void wake_up_devmap_idle(atomic_t *p);
int out_of_line_wait_on_bit(void *word, int, wait_bit_action_f *action, unsigned int mode);
int out_of_line_wait_on_bit_timeout(void *word, int, wait_bit_action_f *action, unsigned int mode, unsigned long timeout);
int out_of_line_wait_on_bit_lock(void *word, int, wait_bit_action_f *action, unsigned int mode);
int out_of_line_wait_on_atomic_t(atomic_t *p, int (*)(atomic_t *), unsigned int mode);
+int out_of_line_wait_on_devmap_idle(atomic_t *p, int (*)(atomic_t *), unsigned int mode);
struct wait_queue_head *bit_waitqueue(void *word, int bit);
extern void __init wait_bit_init(void);
@@ -258,4 +260,12 @@ int wait_on_atomic_t(atomic_t *val, int (*action)(atomic_t *), unsigned mode)
return out_of_line_wait_on_atomic_t(val, action, mode);
}
+static inline
+int wait_on_devmap_idle(atomic_t *val, int (*action)(atomic_t *), unsigned mode)
+{
+ might_sleep();
+ if (atomic_read(val) == 1)
+ return 0;
+ return out_of_line_wait_on_devmap_idle(val, action, mode);
+}
#endif /* _LINUX_WAIT_BIT_H */
diff --git a/kernel/sched/wait_bit.c b/kernel/sched/wait_bit.c
index f8159698aa4d..6ea93149614a 100644
--- a/kernel/sched/wait_bit.c
+++ b/kernel/sched/wait_bit.c
@@ -162,11 +162,17 @@ static inline wait_queue_head_t *atomic_t_waitqueue(atomic_t *p)
return bit_waitqueue(p, 0);
}
-static int wake_atomic_t_function(struct wait_queue_entry *wq_entry, unsigned mode, int sync,
- void *arg)
+static inline struct wait_bit_queue_entry *to_wait_bit_q(
+ struct wait_queue_entry *wq_entry)
+{
+ return container_of(wq_entry, struct wait_bit_queue_entry, wq_entry);
+}
+
+static int wake_atomic_t_function(struct wait_queue_entry *wq_entry,
+ unsigned mode, int sync, void *arg)
{
struct wait_bit_key *key = arg;
- struct wait_bit_queue_entry *wait_bit = container_of(wq_entry, struct wait_bit_queue_entry, wq_entry);
+ struct wait_bit_queue_entry *wait_bit = to_wait_bit_q(wq_entry);
atomic_t *val = key->flags;
if (wait_bit->key.flags != key->flags ||
@@ -176,14 +182,29 @@ static int wake_atomic_t_function(struct wait_queue_entry *wq_entry, unsigned mo
return autoremove_wake_function(wq_entry, mode, sync, key);
}
+static int wake_devmap_idle_function(struct wait_queue_entry *wq_entry,
+ unsigned mode, int sync, void *arg)
+{
+ struct wait_bit_key *key = arg;
+ struct wait_bit_queue_entry *wait_bit = to_wait_bit_q(wq_entry);
+ atomic_t *val = key->flags;
+
+ if (wait_bit->key.flags != key->flags ||
+ wait_bit->key.bit_nr != key->bit_nr ||
+ atomic_read(val) != 1)
+ return 0;
+ return autoremove_wake_function(wq_entry, mode, sync, key);
+}
+
/*
* To allow interruptible waiting and asynchronous (i.e. nonblocking) waiting,
* the actions of __wait_on_atomic_t() are permitted return codes. Nonzero
* return codes halt waiting and return.
*/
static __sched
-int __wait_on_atomic_t(struct wait_queue_head *wq_head, struct wait_bit_queue_entry *wbq_entry,
- int (*action)(atomic_t *), unsigned mode)
+int __wait_on_atomic_t(struct wait_queue_head *wq_head,
+ struct wait_bit_queue_entry *wbq_entry,
+ int (*action)(atomic_t *), unsigned mode, int target)
{
atomic_t *val;
int ret = 0;
@@ -191,10 +212,10 @@ int __wait_on_atomic_t(struct wait_queue_head *wq_head, struct wait_bit_queue_en
do {
prepare_to_wait(wq_head, &wbq_entry->wq_entry, mode);
val = wbq_entry->key.flags;
- if (atomic_read(val) == 0)
+ if (atomic_read(val) == target)
break;
ret = (*action)(val);
- } while (!ret && atomic_read(val) != 0);
+ } while (!ret && atomic_read(val) != target);
finish_wait(wq_head, &wbq_entry->wq_entry);
return ret;
}
@@ -210,16 +231,37 @@ int __wait_on_atomic_t(struct wait_queue_head *wq_head, struct wait_bit_queue_en
}, \
}
+#define DEFINE_WAIT_DEVMAP_IDLE(name, p) \
+ struct wait_bit_queue_entry name = { \
+ .key = __WAIT_ATOMIC_T_KEY_INITIALIZER(p), \
+ .wq_entry = { \
+ .private = current, \
+ .func = wake_devmap_idle_function, \
+ .entry = \
+ LIST_HEAD_INIT((name).wq_entry.entry), \
+ }, \
+ }
+
__sched int out_of_line_wait_on_atomic_t(atomic_t *p, int (*action)(atomic_t *),
unsigned mode)
{
struct wait_queue_head *wq_head = atomic_t_waitqueue(p);
DEFINE_WAIT_ATOMIC_T(wq_entry, p);
- return __wait_on_atomic_t(wq_head, &wq_entry, action, mode);
+ return __wait_on_atomic_t(wq_head, &wq_entry, action, mode, 0);
}
EXPORT_SYMBOL(out_of_line_wait_on_atomic_t);
+__sched int out_of_line_wait_on_devmap_idle(atomic_t *p, int (*action)(atomic_t *),
+ unsigned mode)
+{
+ struct wait_queue_head *wq_head = atomic_t_waitqueue(p);
+ DEFINE_WAIT_DEVMAP_IDLE(wq_entry, p);
+
+ return __wait_on_atomic_t(wq_head, &wq_entry, action, mode, 1);
+}
+EXPORT_SYMBOL(out_of_line_wait_on_devmap_idle);
+
/**
* wake_up_atomic_t - Wake up a waiter on a atomic_t
* @p: The atomic_t being waited on, a kernel virtual address
@@ -235,6 +277,12 @@ void wake_up_atomic_t(atomic_t *p)
}
EXPORT_SYMBOL(wake_up_atomic_t);
+void wake_up_devmap_idle(atomic_t *p)
+{
+ __wake_up_bit(atomic_t_waitqueue(p), p, WAIT_ATOMIC_T_BIT_NR);
+}
+EXPORT_SYMBOL(wake_up_devmap_idle);
+
__sched int bit_wait(struct wait_bit_key *word, int mode)
{
schedule();
