[PATCH 12/17] btrfs: introduce BTRFS_NESTING_LEFT/RIGHT_COW

Josef Bacik
2020-08-10T15:43:13Z

For similar reasons as BTRFS_NESTING_COW, we need
BTRFS_NESTING_LEFT/RIGHT_COW. The pattern is this

lock leaf -> BTRFS_NESTING_NORMAL
cow leaf -> BTRFS_NESTING_COW
split leaf
lock left -> BTRFS_NESTING_LEFT
cow left -> BTRFS_NESTING_LEFT_COW

We need this in order to indicate to lockdep that these locks are
discrete and are being taken in a safe order.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
---
fs/btrfs/ctree.c | 12 ++++++------
fs/btrfs/locking.h | 8 ++++++++
2 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index ea5412cd0f62..6b63b3bcacd4 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -1900,7 +1900,7 @@ static noinline int balance_level(struct btrfs_trans_handle *trans,
btrfs_set_lock_blocking_write(left);
wret = btrfs_cow_block(trans, root, left,
parent, pslot - 1, &left,
- BTRFS_NESTING_COW);
+ BTRFS_NESTING_LEFT_COW);
if (wret) {
ret = wret;
goto enospc;
@@ -1916,7 +1916,7 @@ static noinline int balance_level(struct btrfs_trans_handle *trans,
btrfs_set_lock_blocking_write(right);
wret = btrfs_cow_block(trans, root, right,
parent, pslot + 1, &right,
- BTRFS_NESTING_COW);
+ BTRFS_NESTING_RIGHT_COW);
if (wret) {
ret = wret;
goto enospc;
@@ -2085,7 +2085,7 @@ static noinline int push_nodes_for_insert(struct btrfs_trans_handle *trans,
} else {
ret = btrfs_cow_block(trans, root, left, parent,
pslot - 1, &left,
- BTRFS_NESTING_COW);
+ BTRFS_NESTING_LEFT_COW);
if (ret)
wret = 1;
else {
@@ -2140,7 +2140,7 @@ static noinline int push_nodes_for_insert(struct btrfs_trans_handle *trans,
} else {
ret = btrfs_cow_block(trans, root, right,
parent, pslot + 1,
- &right, BTRFS_NESTING_COW);
+ &right, BTRFS_NESTING_RIGHT_COW);
if (ret)
wret = 1;
else {
@@ -3751,7 +3751,7 @@ static int push_leaf_right(struct btrfs_trans_handle *trans, struct btrfs_root

/* cow and double check */
ret = btrfs_cow_block(trans, root, right, upper,
- slot + 1, &right, BTRFS_NESTING_COW);
+ slot + 1, &right, BTRFS_NESTING_RIGHT_COW);
if (ret)
goto out_unlock;

@@ -3987,7 +3987,7 @@ static int push_leaf_left(struct btrfs_trans_handle *trans, struct btrfs_root
/* cow and double check */
ret = btrfs_cow_block(trans, root, left,
path->nodes[1], slot - 1, &left,
- BTRFS_NESTING_COW);
+ BTRFS_NESTING_LEFT_COW);
if (ret) {
/* we hit -ENOSPC, but it isn't fatal here */
if (ret == -ENOSPC)
diff --git a/fs/btrfs/locking.h b/fs/btrfs/locking.h
index f93e3e10ddbd..31a87477b889 100644
--- a/fs/btrfs/locking.h
+++ b/fs/btrfs/locking.h
@@ -38,6 +38,14 @@ enum btrfs_lock_nesting {
*/
BTRFS_NESTING_LEFT,
BTRFS_NESTING_RIGHT,
+
+ /*
+ * When splitting we will be holding a lock on the left/right node when
+ * we need to cow that node, thus we need a new set of subclasses for
+ * these two operations.
+ */
+ BTRFS_NESTING_LEFT_COW,
+ BTRFS_NESTING_RIGHT_COW,
};

struct btrfs_path;
--
2.24.1