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-rw-r--r--fs/btrfs/locking.c91
1 files changed, 91 insertions, 0 deletions
diff --git a/fs/btrfs/locking.c b/fs/btrfs/locking.c
index 33461b4f9c8b..9063072b399b 100644
--- a/fs/btrfs/locking.c
+++ b/fs/btrfs/locking.c
@@ -14,6 +14,93 @@
#include "locking.h"
/*
+ * Lockdep class keys for extent_buffer->lock's in this root. For a given
+ * eb, the lockdep key is determined by the btrfs_root it belongs to and
+ * the level the eb occupies in the tree.
+ *
+ * Different roots are used for different purposes and may nest inside each
+ * other and they require separate keysets. As lockdep keys should be
+ * static, assign keysets according to the purpose of the root as indicated
+ * by btrfs_root->root_key.objectid. This ensures that all special purpose
+ * roots have separate keysets.
+ *
+ * Lock-nesting across peer nodes is always done with the immediate parent
+ * node locked thus preventing deadlock. As lockdep doesn't know this, use
+ * subclass to avoid triggering lockdep warning in such cases.
+ *
+ * The key is set by the readpage_end_io_hook after the buffer has passed
+ * csum validation but before the pages are unlocked. It is also set by
+ * btrfs_init_new_buffer on freshly allocated blocks.
+ *
+ * We also add a check to make sure the highest level of the tree is the
+ * same as our lockdep setup here. If BTRFS_MAX_LEVEL changes, this code
+ * needs update as well.
+ */
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+#if BTRFS_MAX_LEVEL != 8
+#error
+#endif
+
+#define DEFINE_LEVEL(stem, level) \
+ .names[level] = "btrfs-" stem "-0" #level,
+
+#define DEFINE_NAME(stem) \
+ DEFINE_LEVEL(stem, 0) \
+ DEFINE_LEVEL(stem, 1) \
+ DEFINE_LEVEL(stem, 2) \
+ DEFINE_LEVEL(stem, 3) \
+ DEFINE_LEVEL(stem, 4) \
+ DEFINE_LEVEL(stem, 5) \
+ DEFINE_LEVEL(stem, 6) \
+ DEFINE_LEVEL(stem, 7)
+
+static struct btrfs_lockdep_keyset {
+ u64 id; /* root objectid */
+ /* Longest entry: btrfs-free-space-00 */
+ char names[BTRFS_MAX_LEVEL][20];
+ struct lock_class_key keys[BTRFS_MAX_LEVEL];
+} btrfs_lockdep_keysets[] = {
+ { .id = BTRFS_ROOT_TREE_OBJECTID, DEFINE_NAME("root") },
+ { .id = BTRFS_EXTENT_TREE_OBJECTID, DEFINE_NAME("extent") },
+ { .id = BTRFS_CHUNK_TREE_OBJECTID, DEFINE_NAME("chunk") },
+ { .id = BTRFS_DEV_TREE_OBJECTID, DEFINE_NAME("dev") },
+ { .id = BTRFS_CSUM_TREE_OBJECTID, DEFINE_NAME("csum") },
+ { .id = BTRFS_QUOTA_TREE_OBJECTID, DEFINE_NAME("quota") },
+ { .id = BTRFS_TREE_LOG_OBJECTID, DEFINE_NAME("log") },
+ { .id = BTRFS_TREE_RELOC_OBJECTID, DEFINE_NAME("treloc") },
+ { .id = BTRFS_DATA_RELOC_TREE_OBJECTID, DEFINE_NAME("dreloc") },
+ { .id = BTRFS_UUID_TREE_OBJECTID, DEFINE_NAME("uuid") },
+ { .id = BTRFS_FREE_SPACE_TREE_OBJECTID, DEFINE_NAME("free-space") },
+ { .id = 0, DEFINE_NAME("tree") },
+};
+
+#undef DEFINE_LEVEL
+#undef DEFINE_NAME
+
+void btrfs_set_buffer_lockdep_class(u64 objectid, struct extent_buffer *eb, int level)
+{
+ struct btrfs_lockdep_keyset *ks;
+
+ BUG_ON(level >= ARRAY_SIZE(ks->keys));
+
+ /* Find the matching keyset, id 0 is the default entry */
+ for (ks = btrfs_lockdep_keysets; ks->id; ks++)
+ if (ks->id == objectid)
+ break;
+
+ lockdep_set_class_and_name(&eb->lock, &ks->keys[level], ks->names[level]);
+}
+
+void btrfs_maybe_reset_lockdep_class(struct btrfs_root *root, struct extent_buffer *eb)
+{
+ if (test_bit(BTRFS_ROOT_RESET_LOCKDEP_CLASS, &root->state))
+ btrfs_set_buffer_lockdep_class(root->root_key.objectid,
+ eb, btrfs_header_level(eb));
+}
+
+#endif
+
+/*
* Extent buffer locking
* =====================
*
@@ -164,6 +251,8 @@ struct extent_buffer *btrfs_lock_root_node(struct btrfs_root *root)
while (1) {
eb = btrfs_root_node(root);
+
+ btrfs_maybe_reset_lockdep_class(root, eb);
btrfs_tree_lock(eb);
if (eb == root->node)
break;
@@ -185,6 +274,8 @@ struct extent_buffer *btrfs_read_lock_root_node(struct btrfs_root *root)
while (1) {
eb = btrfs_root_node(root);
+
+ btrfs_maybe_reset_lockdep_class(root, eb);
btrfs_tree_read_lock(eb);
if (eb == root->node)
break;