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Diffstat (limited to 'fs/btrfs/locking.c')
-rw-r--r--fs/btrfs/locking.c109
1 files changed, 61 insertions, 48 deletions
diff --git a/fs/btrfs/locking.c b/fs/btrfs/locking.c
index 5e178d8f716..5665d214924 100644
--- a/fs/btrfs/locking.c
+++ b/fs/btrfs/locking.c
@@ -24,7 +24,7 @@
#include "extent_io.h"
#include "locking.h"
-void btrfs_assert_tree_read_locked(struct extent_buffer *eb);
+static void btrfs_assert_tree_read_locked(struct extent_buffer *eb);
/*
* if we currently have a spinning reader or writer lock
@@ -33,14 +33,14 @@ void btrfs_assert_tree_read_locked(struct extent_buffer *eb);
*/
void btrfs_set_lock_blocking_rw(struct extent_buffer *eb, int rw)
{
- if (eb->lock_nested) {
- read_lock(&eb->lock);
- if (eb->lock_nested && current->pid == eb->lock_owner) {
- read_unlock(&eb->lock);
- return;
- }
- read_unlock(&eb->lock);
- }
+ /*
+ * 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 (rw == BTRFS_WRITE_LOCK) {
if (atomic_read(&eb->blocking_writers) == 0) {
WARN_ON(atomic_read(&eb->spinning_writers) != 1);
@@ -65,26 +65,29 @@ void btrfs_set_lock_blocking_rw(struct extent_buffer *eb, int rw)
*/
void btrfs_clear_lock_blocking_rw(struct extent_buffer *eb, int rw)
{
- if (eb->lock_nested) {
- read_lock(&eb->lock);
- if (&eb->lock_nested && current->pid == eb->lock_owner) {
- read_unlock(&eb->lock);
- return;
- }
- read_unlock(&eb->lock);
- }
+ /*
+ * 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 (rw == BTRFS_WRITE_LOCK_BLOCKING) {
BUG_ON(atomic_read(&eb->blocking_writers) != 1);
write_lock(&eb->lock);
WARN_ON(atomic_read(&eb->spinning_writers));
atomic_inc(&eb->spinning_writers);
- if (atomic_dec_and_test(&eb->blocking_writers))
+ if (atomic_dec_and_test(&eb->blocking_writers) &&
+ waitqueue_active(&eb->write_lock_wq))
wake_up(&eb->write_lock_wq);
} else if (rw == BTRFS_READ_LOCK_BLOCKING) {
BUG_ON(atomic_read(&eb->blocking_readers) == 0);
read_lock(&eb->lock);
atomic_inc(&eb->spinning_readers);
- if (atomic_dec_and_test(&eb->blocking_readers))
+ if (atomic_dec_and_test(&eb->blocking_readers) &&
+ waitqueue_active(&eb->read_lock_wq))
wake_up(&eb->read_lock_wq);
}
return;
@@ -97,6 +100,9 @@ void btrfs_clear_lock_blocking_rw(struct extent_buffer *eb, int rw)
void btrfs_tree_read_lock(struct extent_buffer *eb)
{
again:
+ BUG_ON(!atomic_read(&eb->blocking_writers) &&
+ current->pid == eb->lock_owner);
+
read_lock(&eb->lock);
if (atomic_read(&eb->blocking_writers) &&
current->pid == eb->lock_owner) {
@@ -111,11 +117,10 @@ again:
read_unlock(&eb->lock);
return;
}
- read_unlock(&eb->lock);
- wait_event(eb->write_lock_wq, atomic_read(&eb->blocking_writers) == 0);
- read_lock(&eb->lock);
if (atomic_read(&eb->blocking_writers)) {
read_unlock(&eb->lock);
+ wait_event(eb->write_lock_wq,
+ atomic_read(&eb->blocking_writers) == 0);
goto again;
}
atomic_inc(&eb->read_locks);
@@ -131,7 +136,9 @@ int btrfs_try_tree_read_lock(struct extent_buffer *eb)
if (atomic_read(&eb->blocking_writers))
return 0;
- read_lock(&eb->lock);
+ if (!read_trylock(&eb->lock))
+ return 0;
+
if (atomic_read(&eb->blocking_writers)) {
read_unlock(&eb->lock);
return 0;
@@ -150,7 +157,10 @@ int btrfs_try_tree_write_lock(struct extent_buffer *eb)
if (atomic_read(&eb->blocking_writers) ||
atomic_read(&eb->blocking_readers))
return 0;
- write_lock(&eb->lock);
+
+ if (!write_trylock(&eb->lock))
+ return 0;
+
if (atomic_read(&eb->blocking_writers) ||
atomic_read(&eb->blocking_readers)) {
write_unlock(&eb->lock);
@@ -167,14 +177,15 @@ int btrfs_try_tree_write_lock(struct extent_buffer *eb)
*/
void btrfs_tree_read_unlock(struct extent_buffer *eb)
{
- if (eb->lock_nested) {
- read_lock(&eb->lock);
- if (eb->lock_nested && current->pid == eb->lock_owner) {
- eb->lock_nested = 0;
- read_unlock(&eb->lock);
- return;
- }
- read_unlock(&eb->lock);
+ /*
+ * 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 = 0;
+ return;
}
btrfs_assert_tree_read_locked(eb);
WARN_ON(atomic_read(&eb->spinning_readers) == 0);
@@ -188,18 +199,20 @@ void btrfs_tree_read_unlock(struct extent_buffer *eb)
*/
void btrfs_tree_read_unlock_blocking(struct extent_buffer *eb)
{
- if (eb->lock_nested) {
- read_lock(&eb->lock);
- if (eb->lock_nested && current->pid == eb->lock_owner) {
- eb->lock_nested = 0;
- read_unlock(&eb->lock);
- return;
- }
- read_unlock(&eb->lock);
+ /*
+ * 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 = 0;
+ return;
}
btrfs_assert_tree_read_locked(eb);
WARN_ON(atomic_read(&eb->blocking_readers) == 0);
- if (atomic_dec_and_test(&eb->blocking_readers))
+ if (atomic_dec_and_test(&eb->blocking_readers) &&
+ waitqueue_active(&eb->read_lock_wq))
wake_up(&eb->read_lock_wq);
atomic_dec(&eb->read_locks);
}
@@ -208,7 +221,7 @@ void btrfs_tree_read_unlock_blocking(struct extent_buffer *eb)
* take a spinning write lock. This will wait for both
* blocking readers or writers
*/
-int btrfs_tree_lock(struct extent_buffer *eb)
+void btrfs_tree_lock(struct extent_buffer *eb)
{
again:
wait_event(eb->read_lock_wq, atomic_read(&eb->blocking_readers) == 0);
@@ -230,32 +243,32 @@ again:
atomic_inc(&eb->spinning_writers);
atomic_inc(&eb->write_locks);
eb->lock_owner = current->pid;
- return 0;
}
/*
* drop a spinning or a blocking write lock.
*/
-int btrfs_tree_unlock(struct extent_buffer *eb)
+void btrfs_tree_unlock(struct extent_buffer *eb)
{
int blockers = atomic_read(&eb->blocking_writers);
BUG_ON(blockers > 1);
btrfs_assert_tree_locked(eb);
+ eb->lock_owner = 0;
atomic_dec(&eb->write_locks);
if (blockers) {
WARN_ON(atomic_read(&eb->spinning_writers));
atomic_dec(&eb->blocking_writers);
- smp_wmb();
- wake_up(&eb->write_lock_wq);
+ smp_mb();
+ if (waitqueue_active(&eb->write_lock_wq))
+ wake_up(&eb->write_lock_wq);
} else {
WARN_ON(atomic_read(&eb->spinning_writers) != 1);
atomic_dec(&eb->spinning_writers);
write_unlock(&eb->lock);
}
- return 0;
}
void btrfs_assert_tree_locked(struct extent_buffer *eb)
@@ -263,7 +276,7 @@ void btrfs_assert_tree_locked(struct extent_buffer *eb)
BUG_ON(!atomic_read(&eb->write_locks));
}
-void btrfs_assert_tree_read_locked(struct extent_buffer *eb)
+static void btrfs_assert_tree_read_locked(struct extent_buffer *eb)
{
BUG_ON(!atomic_read(&eb->read_locks));
}
generated by cgit v1.2.3-70-g09d2 (git 2.46.0) at 2025-11-09 20:39:12 +0000