345 строки
9.0 KiB
C
345 строки
9.0 KiB
C
// SPDX-License-Identifier: GPL-2.0
|
|
/*
|
|
* Copyright (C) 2008 Oracle. All rights reserved.
|
|
*/
|
|
|
|
#include <linux/sched.h>
|
|
#include <linux/pagemap.h>
|
|
#include <linux/spinlock.h>
|
|
#include <linux/page-flags.h>
|
|
#include <asm/bug.h>
|
|
#include "misc.h"
|
|
#include "ctree.h"
|
|
#include "extent_io.h"
|
|
#include "locking.h"
|
|
|
|
#ifdef CONFIG_BTRFS_DEBUG
|
|
static inline void btrfs_assert_spinning_writers_get(struct extent_buffer *eb)
|
|
{
|
|
WARN_ON(eb->spinning_writers);
|
|
eb->spinning_writers++;
|
|
}
|
|
|
|
static inline void btrfs_assert_spinning_writers_put(struct extent_buffer *eb)
|
|
{
|
|
WARN_ON(eb->spinning_writers != 1);
|
|
eb->spinning_writers--;
|
|
}
|
|
|
|
static inline void btrfs_assert_no_spinning_writers(struct extent_buffer *eb)
|
|
{
|
|
WARN_ON(eb->spinning_writers);
|
|
}
|
|
|
|
static inline void btrfs_assert_spinning_readers_get(struct extent_buffer *eb)
|
|
{
|
|
atomic_inc(&eb->spinning_readers);
|
|
}
|
|
|
|
static inline void btrfs_assert_spinning_readers_put(struct extent_buffer *eb)
|
|
{
|
|
WARN_ON(atomic_read(&eb->spinning_readers) == 0);
|
|
atomic_dec(&eb->spinning_readers);
|
|
}
|
|
|
|
static inline void btrfs_assert_tree_read_locks_get(struct extent_buffer *eb)
|
|
{
|
|
atomic_inc(&eb->read_locks);
|
|
}
|
|
|
|
static inline void btrfs_assert_tree_read_locks_put(struct extent_buffer *eb)
|
|
{
|
|
atomic_dec(&eb->read_locks);
|
|
}
|
|
|
|
static inline void btrfs_assert_tree_read_locked(struct extent_buffer *eb)
|
|
{
|
|
BUG_ON(!atomic_read(&eb->read_locks));
|
|
}
|
|
|
|
static inline void btrfs_assert_tree_write_locks_get(struct extent_buffer *eb)
|
|
{
|
|
eb->write_locks++;
|
|
}
|
|
|
|
static inline void btrfs_assert_tree_write_locks_put(struct extent_buffer *eb)
|
|
{
|
|
eb->write_locks--;
|
|
}
|
|
|
|
#else
|
|
static void btrfs_assert_spinning_writers_get(struct extent_buffer *eb) { }
|
|
static void btrfs_assert_spinning_writers_put(struct extent_buffer *eb) { }
|
|
static void btrfs_assert_no_spinning_writers(struct extent_buffer *eb) { }
|
|
static void btrfs_assert_spinning_readers_put(struct extent_buffer *eb) { }
|
|
static void btrfs_assert_spinning_readers_get(struct extent_buffer *eb) { }
|
|
static void btrfs_assert_tree_read_locked(struct extent_buffer *eb) { }
|
|
static void btrfs_assert_tree_read_locks_get(struct extent_buffer *eb) { }
|
|
static void btrfs_assert_tree_read_locks_put(struct extent_buffer *eb) { }
|
|
static void btrfs_assert_tree_write_locks_get(struct extent_buffer *eb) { }
|
|
static void btrfs_assert_tree_write_locks_put(struct extent_buffer *eb) { }
|
|
#endif
|
|
|
|
void btrfs_set_lock_blocking_read(struct extent_buffer *eb)
|
|
{
|
|
trace_btrfs_set_lock_blocking_read(eb);
|
|
/*
|
|
* No lock is required. The lock owner may change if we have a read
|
|
* lock, but it won't change to or away from us. If we have the write
|
|
* lock, we are the owner and it'll never change.
|
|
*/
|
|
if (eb->lock_nested && current->pid == eb->lock_owner)
|
|
return;
|
|
btrfs_assert_tree_read_locked(eb);
|
|
atomic_inc(&eb->blocking_readers);
|
|
btrfs_assert_spinning_readers_put(eb);
|
|
read_unlock(&eb->lock);
|
|
}
|
|
|
|
void btrfs_set_lock_blocking_write(struct extent_buffer *eb)
|
|
{
|
|
trace_btrfs_set_lock_blocking_write(eb);
|
|
/*
|
|
* No lock is required. The lock owner may change if we have a read
|
|
* lock, but it won't change to or away from us. If we have the write
|
|
* lock, we are the owner and it'll never change.
|
|
*/
|
|
if (eb->lock_nested && current->pid == eb->lock_owner)
|
|
return;
|
|
if (eb->blocking_writers == 0) {
|
|
btrfs_assert_spinning_writers_put(eb);
|
|
btrfs_assert_tree_locked(eb);
|
|
eb->blocking_writers++;
|
|
write_unlock(&eb->lock);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* take a spinning read lock. This will wait for any blocking
|
|
* writers
|
|
*/
|
|
void btrfs_tree_read_lock(struct extent_buffer *eb)
|
|
{
|
|
u64 start_ns = 0;
|
|
|
|
if (trace_btrfs_tree_read_lock_enabled())
|
|
start_ns = ktime_get_ns();
|
|
again:
|
|
read_lock(&eb->lock);
|
|
BUG_ON(eb->blocking_writers == 0 &&
|
|
current->pid == eb->lock_owner);
|
|
if (eb->blocking_writers && current->pid == eb->lock_owner) {
|
|
/*
|
|
* This extent is already write-locked by our thread. We allow
|
|
* an additional read lock to be added because it's for the same
|
|
* thread. btrfs_find_all_roots() depends on this as it may be
|
|
* called on a partly (write-)locked tree.
|
|
*/
|
|
BUG_ON(eb->lock_nested);
|
|
eb->lock_nested = true;
|
|
read_unlock(&eb->lock);
|
|
trace_btrfs_tree_read_lock(eb, start_ns);
|
|
return;
|
|
}
|
|
if (eb->blocking_writers) {
|
|
read_unlock(&eb->lock);
|
|
wait_event(eb->write_lock_wq,
|
|
eb->blocking_writers == 0);
|
|
goto again;
|
|
}
|
|
btrfs_assert_tree_read_locks_get(eb);
|
|
btrfs_assert_spinning_readers_get(eb);
|
|
trace_btrfs_tree_read_lock(eb, start_ns);
|
|
}
|
|
|
|
/*
|
|
* take a spinning read lock.
|
|
* returns 1 if we get the read lock and 0 if we don't
|
|
* this won't wait for blocking writers
|
|
*/
|
|
int btrfs_tree_read_lock_atomic(struct extent_buffer *eb)
|
|
{
|
|
if (eb->blocking_writers)
|
|
return 0;
|
|
|
|
read_lock(&eb->lock);
|
|
if (eb->blocking_writers) {
|
|
read_unlock(&eb->lock);
|
|
return 0;
|
|
}
|
|
btrfs_assert_tree_read_locks_get(eb);
|
|
btrfs_assert_spinning_readers_get(eb);
|
|
trace_btrfs_tree_read_lock_atomic(eb);
|
|
return 1;
|
|
}
|
|
|
|
/*
|
|
* returns 1 if we get the read lock and 0 if we don't
|
|
* this won't wait for blocking writers
|
|
*/
|
|
int btrfs_try_tree_read_lock(struct extent_buffer *eb)
|
|
{
|
|
if (eb->blocking_writers)
|
|
return 0;
|
|
|
|
if (!read_trylock(&eb->lock))
|
|
return 0;
|
|
|
|
if (eb->blocking_writers) {
|
|
read_unlock(&eb->lock);
|
|
return 0;
|
|
}
|
|
btrfs_assert_tree_read_locks_get(eb);
|
|
btrfs_assert_spinning_readers_get(eb);
|
|
trace_btrfs_try_tree_read_lock(eb);
|
|
return 1;
|
|
}
|
|
|
|
/*
|
|
* returns 1 if we get the read lock and 0 if we don't
|
|
* this won't wait for blocking writers or readers
|
|
*/
|
|
int btrfs_try_tree_write_lock(struct extent_buffer *eb)
|
|
{
|
|
if (eb->blocking_writers || atomic_read(&eb->blocking_readers))
|
|
return 0;
|
|
|
|
write_lock(&eb->lock);
|
|
if (eb->blocking_writers || atomic_read(&eb->blocking_readers)) {
|
|
write_unlock(&eb->lock);
|
|
return 0;
|
|
}
|
|
btrfs_assert_tree_write_locks_get(eb);
|
|
btrfs_assert_spinning_writers_get(eb);
|
|
eb->lock_owner = current->pid;
|
|
trace_btrfs_try_tree_write_lock(eb);
|
|
return 1;
|
|
}
|
|
|
|
/*
|
|
* drop a spinning read lock
|
|
*/
|
|
void btrfs_tree_read_unlock(struct extent_buffer *eb)
|
|
{
|
|
trace_btrfs_tree_read_unlock(eb);
|
|
/*
|
|
* if we're nested, we have the write lock. No new locking
|
|
* is needed as long as we are the lock owner.
|
|
* The write unlock will do a barrier for us, and the lock_nested
|
|
* field only matters to the lock owner.
|
|
*/
|
|
if (eb->lock_nested && current->pid == eb->lock_owner) {
|
|
eb->lock_nested = false;
|
|
return;
|
|
}
|
|
btrfs_assert_tree_read_locked(eb);
|
|
btrfs_assert_spinning_readers_put(eb);
|
|
btrfs_assert_tree_read_locks_put(eb);
|
|
read_unlock(&eb->lock);
|
|
}
|
|
|
|
/*
|
|
* drop a blocking read lock
|
|
*/
|
|
void btrfs_tree_read_unlock_blocking(struct extent_buffer *eb)
|
|
{
|
|
trace_btrfs_tree_read_unlock_blocking(eb);
|
|
/*
|
|
* if we're nested, we have the write lock. No new locking
|
|
* is needed as long as we are the lock owner.
|
|
* The write unlock will do a barrier for us, and the lock_nested
|
|
* field only matters to the lock owner.
|
|
*/
|
|
if (eb->lock_nested && current->pid == eb->lock_owner) {
|
|
eb->lock_nested = false;
|
|
return;
|
|
}
|
|
btrfs_assert_tree_read_locked(eb);
|
|
WARN_ON(atomic_read(&eb->blocking_readers) == 0);
|
|
/* atomic_dec_and_test implies a barrier */
|
|
if (atomic_dec_and_test(&eb->blocking_readers))
|
|
cond_wake_up_nomb(&eb->read_lock_wq);
|
|
btrfs_assert_tree_read_locks_put(eb);
|
|
}
|
|
|
|
/*
|
|
* take a spinning write lock. This will wait for both
|
|
* blocking readers or writers
|
|
*/
|
|
void btrfs_tree_lock(struct extent_buffer *eb)
|
|
{
|
|
u64 start_ns = 0;
|
|
|
|
if (trace_btrfs_tree_lock_enabled())
|
|
start_ns = ktime_get_ns();
|
|
|
|
WARN_ON(eb->lock_owner == current->pid);
|
|
again:
|
|
wait_event(eb->read_lock_wq, atomic_read(&eb->blocking_readers) == 0);
|
|
wait_event(eb->write_lock_wq, eb->blocking_writers == 0);
|
|
write_lock(&eb->lock);
|
|
if (atomic_read(&eb->blocking_readers) || eb->blocking_writers) {
|
|
write_unlock(&eb->lock);
|
|
goto again;
|
|
}
|
|
btrfs_assert_spinning_writers_get(eb);
|
|
btrfs_assert_tree_write_locks_get(eb);
|
|
eb->lock_owner = current->pid;
|
|
trace_btrfs_tree_lock(eb, start_ns);
|
|
}
|
|
|
|
/*
|
|
* drop a spinning or a blocking write lock.
|
|
*/
|
|
void btrfs_tree_unlock(struct extent_buffer *eb)
|
|
{
|
|
int blockers = eb->blocking_writers;
|
|
|
|
BUG_ON(blockers > 1);
|
|
|
|
btrfs_assert_tree_locked(eb);
|
|
trace_btrfs_tree_unlock(eb);
|
|
eb->lock_owner = 0;
|
|
btrfs_assert_tree_write_locks_put(eb);
|
|
|
|
if (blockers) {
|
|
btrfs_assert_no_spinning_writers(eb);
|
|
eb->blocking_writers--;
|
|
/*
|
|
* We need to order modifying blocking_writers above with
|
|
* actually waking up the sleepers to ensure they see the
|
|
* updated value of blocking_writers
|
|
*/
|
|
cond_wake_up(&eb->write_lock_wq);
|
|
} else {
|
|
btrfs_assert_spinning_writers_put(eb);
|
|
write_unlock(&eb->lock);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Set all locked nodes in the path to blocking locks. This should be done
|
|
* before scheduling
|
|
*/
|
|
void btrfs_set_path_blocking(struct btrfs_path *p)
|
|
{
|
|
int i;
|
|
|
|
for (i = 0; i < BTRFS_MAX_LEVEL; i++) {
|
|
if (!p->nodes[i] || !p->locks[i])
|
|
continue;
|
|
/*
|
|
* If we currently have a spinning reader or writer lock this
|
|
* will bump the count of blocking holders and drop the
|
|
* spinlock.
|
|
*/
|
|
if (p->locks[i] == BTRFS_READ_LOCK) {
|
|
btrfs_set_lock_blocking_read(p->nodes[i]);
|
|
p->locks[i] = BTRFS_READ_LOCK_BLOCKING;
|
|
} else if (p->locks[i] == BTRFS_WRITE_LOCK) {
|
|
btrfs_set_lock_blocking_write(p->nodes[i]);
|
|
p->locks[i] = BTRFS_WRITE_LOCK_BLOCKING;
|
|
}
|
|
}
|
|
}
|