btrfs: introduce BTRFS_NESTING_LEFT/RIGHT_COW

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>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index 94af1f385ea67763adfceac92a8c947c77373ea6..ecf8bf240d73aa3d500739caa0d8933f55156e06 100644 (file)
--- 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 {
@@ -3815,7 +3815,7 @@ 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;
 
@@ -4057,7 +4057,7 @@ 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 5844bc1c84104bc4e1a1e6f44edef0bf7db9b431..16563bc486c701f11bfd687d4d2d66aa21374636 100644 (file)
--- a/fs/btrfs/locking.h
+++ b/fs/btrfs/locking.h
@@ -44,6 +44,14 @@ 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,
+
        /*
         * We are limited to MAX_LOCKDEP_SUBLCLASSES number of subclasses, so
         * add this in here and add a static_assert to keep us from going over