[PATCH 07/17] btrfs: rename eb->lock_nested to eb->lock_recursed

Josef Bacik
2020-08-10T15:43:05Z

Nested locking with lockdep and everything else refers to lock hierarchy
within the same lock map. This is how we indicate the same locks for
different objects are ok to take in a specific order, for our use case
that would be to take the lock on a leaf and then take a lock on an
adjacent leaf.

What ->lock_nested _actually_ refers to is if we happen to already be
holding the write lock on the extent buffer and we're allowing a read
lock to be taken on that extent buffer, which is recursion. Rename this
so we don't get confused when we switch to a rwsem and have to start
using the _nested helpers.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
---
fs/btrfs/extent_io.c | 2 +-
fs/btrfs/extent_io.h | 2 +-
fs/btrfs/locking.c | 22 +++++++++++-----------
3 files changed, 13 insertions(+), 13 deletions(-)

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index c15ab6c1897f..16b4e7655a96 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -4988,7 +4988,7 @@ __alloc_extent_buffer(struct btrfs_fs_info *fs_info, u64 start,
rwlock_init(&eb->lock);
atomic_set(&eb->blocking_readers, 0);
eb->blocking_writers = 0;
- eb->lock_nested = false;
+ eb->lock_recursed = false;
init_waitqueue_head(&eb->write_lock_wq);
init_waitqueue_head(&eb->read_lock_wq);

diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
index 30794ae58498..9e1e22f1586a 100644
--- a/fs/btrfs/extent_io.h
+++ b/fs/btrfs/extent_io.h
@@ -102,7 +102,7 @@ struct extent_buffer {

int blocking_writers;
atomic_t blocking_readers;
- bool lock_nested;
+ bool lock_recursed;
/* >= 0 if eb belongs to a log tree, -1 otherwise */
short log_index;

diff --git a/fs/btrfs/locking.c b/fs/btrfs/locking.c
index f75612e18a82..8e3d107a6192 100644
--- a/fs/btrfs/locking.c
+++ b/fs/btrfs/locking.c
@@ -57,7 +57,7 @@
* performance reasons.
*
*
- * Lock nesting
+ * Lock recursion
* ------------
*
* A write operation on a tree might indirectly start a look up on the same
@@ -201,7 +201,7 @@ void btrfs_set_lock_blocking_read(struct extent_buffer *eb)
* 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)
+ if (eb->lock_recursed && current->pid == eb->lock_owner)
return;
btrfs_assert_tree_read_locked(eb);
atomic_inc(&eb->blocking_readers);
@@ -225,7 +225,7 @@ void btrfs_set_lock_blocking_write(struct extent_buffer *eb)
* 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)
+ if (eb->lock_recursed && current->pid == eb->lock_owner)
return;
if (eb->blocking_writers == 0) {
btrfs_assert_spinning_writers_put(eb);
@@ -263,8 +263,8 @@ void btrfs_tree_read_lock(struct extent_buffer *eb)
* depends on this as it may be called on a partly
* (write-)locked tree.
*/
- BUG_ON(eb->lock_nested);
- eb->lock_nested = true;
+ BUG_ON(eb->lock_recursed);
+ eb->lock_recursed = true;
read_unlock(&eb->lock);
trace_btrfs_tree_read_lock(eb, start_ns);
return;
@@ -362,11 +362,11 @@ void btrfs_tree_read_unlock(struct extent_buffer *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
+ * The write unlock will do a barrier for us, and the lock_recursed
* field only matters to the lock owner.
*/
- if (eb->lock_nested && current->pid == eb->lock_owner) {
- eb->lock_nested = false;
+ if (eb->lock_recursed && current->pid == eb->lock_owner) {
+ eb->lock_recursed = false;
return;
}
btrfs_assert_tree_read_locked(eb);
@@ -388,11 +388,11 @@ void btrfs_tree_read_unlock_blocking(struct extent_buffer *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
+ * The write unlock will do a barrier for us, and the lock_recursed
* field only matters to the lock owner.
*/
- if (eb->lock_nested && current->pid == eb->lock_owner) {
- eb->lock_nested = false;
+ if (eb->lock_recursed && current->pid == eb->lock_owner) {
+ eb->lock_recursed = false;
return;
}
btrfs_assert_tree_read_locked(eb);
--
2.24.1