1 files changed, 62 insertions, 9 deletions

diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index c58245797f30..995d4b8b1cfd 100644
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -517,6 +517,34 @@ static int update_backref_cache(struct btrfs_trans_handle *trans,
 	return 1;
 }
 
+static bool reloc_root_is_dead(struct btrfs_root *root)
+{
+	/*
+	 * Pair with set_bit/clear_bit in clean_dirty_subvols and
+	 * btrfs_update_reloc_root. We need to see the updated bit before
+	 * trying to access reloc_root
+	 */
+	smp_rmb();
+	if (test_bit(BTRFS_ROOT_DEAD_RELOC_TREE, &root->state))
+		return true;
+	return false;
+}
+
+/*
+ * Check if this subvolume tree has valid reloc tree.
+ *
+ * Reloc tree after swap is considered dead, thus not considered as valid.
+ * This is enough for most callers, as they don't distinguish dead reloc root
+ * from no reloc root.  But should_ignore_root() below is a special case.
+ */
+static bool have_reloc_root(struct btrfs_root *root)
+{
+	if (reloc_root_is_dead(root))
+		return false;
+	if (!root->reloc_root)
+		return false;
+	return true;
+}
 
 static int should_ignore_root(struct btrfs_root *root)
 {
@@ -525,6 +553,10 @@ static int should_ignore_root(struct btrfs_root *root)
 	if (!test_bit(BTRFS_ROOT_REF_COWS, &root->state))
 		return 0;
 
+	/* This root has been merged with its reloc tree, we can ignore it */
+	if (reloc_root_is_dead(root))
+		return 1;
+
 	reloc_root = root->reloc_root;
 	if (!reloc_root)
 		return 0;
@@ -1439,7 +1471,7 @@ int btrfs_init_reloc_root(struct btrfs_trans_handle *trans,
 	 * The subvolume has reloc tree but the swap is finished, no need to
 	 * create/update the dead reloc tree
 	 */
-	if (test_bit(BTRFS_ROOT_DEAD_RELOC_TREE, &root->state))
+	if (reloc_root_is_dead(root))
 		return 0;
 
 	if (root->reloc_root) {
@@ -1478,8 +1510,7 @@ int btrfs_update_reloc_root(struct btrfs_trans_handle *trans,
 	struct btrfs_root_item *root_item;
 	int ret;
 
-	if (test_bit(BTRFS_ROOT_DEAD_RELOC_TREE, &root->state) ||
-	    !root->reloc_root)
+	if (!have_reloc_root(root))
 		goto out;
 
 	reloc_root = root->reloc_root;
@@ -1489,6 +1520,11 @@ int btrfs_update_reloc_root(struct btrfs_trans_handle *trans,
 	if (fs_info->reloc_ctl->merge_reloc_tree &&
 	    btrfs_root_refs(root_item) == 0) {
 		set_bit(BTRFS_ROOT_DEAD_RELOC_TREE, &root->state);
+		/*
+		 * Mark the tree as dead before we change reloc_root so
+		 * have_reloc_root will not touch it from now on.
+		 */
+		smp_wmb();
 		__del_reloc_root(reloc_root);
 	}
 
@@ -2201,6 +2237,11 @@ static int clean_dirty_subvols(struct reloc_control *rc)
 				if (ret2 < 0 && !ret)
 					ret = ret2;
 			}
+			/*
+			 * Need barrier to ensure clear_bit() only happens after
+			 * root->reloc_root = NULL. Pairs with have_reloc_root.
+			 */
+			smp_wmb();
 			clear_bit(BTRFS_ROOT_DEAD_RELOC_TREE, &root->state);
 			btrfs_put_fs_root(root);
 		} else {
@@ -4291,6 +4332,15 @@ static void describe_relocation(struct btrfs_fs_info *fs_info,
 		   block_group->start, buf);
 }
 
+static const char *stage_to_string(int stage)
+{
+	if (stage == MOVE_DATA_EXTENTS)
+		return "move data extents";
+	if (stage == UPDATE_DATA_PTRS)
+		return "update data pointers";
+	return "unknown";
+}
+
 /*
  * function to relocate all extents in a block group.
  */
@@ -4365,12 +4415,15 @@ int btrfs_relocate_block_group(struct btrfs_fs_info *fs_info, u64 group_start)
 				 rc->block_group->length);
 
 	while (1) {
+		int finishes_stage;
+
 		mutex_lock(&fs_info->cleaner_mutex);
 		ret = relocate_block_group(rc);
 		mutex_unlock(&fs_info->cleaner_mutex);
 		if (ret < 0)
 			err = ret;
 
+		finishes_stage = rc->stage;
 		/*
 		 * We may have gotten ENOSPC after we already dirtied some
 		 * extents.  If writeout happens while we're relocating a
@@ -4396,8 +4449,8 @@ int btrfs_relocate_block_group(struct btrfs_fs_info *fs_info, u64 group_start)
 		if (rc->extents_found == 0)
 			break;
 
-		btrfs_info(fs_info, "found %llu extents", rc->extents_found);
-
+		btrfs_info(fs_info, "found %llu extents, stage: %s",
+			   rc->extents_found, stage_to_string(finishes_stage));
 	}
 
 	WARN_ON(rc->block_group->pinned > 0);
@@ -4615,7 +4668,7 @@ int btrfs_reloc_clone_csums(struct inode *inode, u64 file_pos, u64 len)
 	LIST_HEAD(list);
 
 	ordered = btrfs_lookup_ordered_extent(inode, file_pos);
-	BUG_ON(ordered->file_offset != file_pos || ordered->len != len);
+	BUG_ON(ordered->file_offset != file_pos || ordered->num_bytes != len);
 
 	disk_bytenr = file_pos + BTRFS_I(inode)->index_cnt;
 	ret = btrfs_lookup_csums_range(fs_info->csum_root, disk_bytenr,
@@ -4639,7 +4692,7 @@ int btrfs_reloc_clone_csums(struct inode *inode, u64 file_pos, u64 len)
 		 * disk_len vs real len like with real inodes since it's all
 		 * disk length.
 		 */
-		new_bytenr = ordered->start + (sums->bytenr - disk_bytenr);
+		new_bytenr = ordered->disk_bytenr + sums->bytenr - disk_bytenr;
 		sums->bytenr = new_bytenr;
 
 		btrfs_add_ordered_sum(ordered, sums);
@@ -4718,7 +4771,7 @@ void btrfs_reloc_pre_snapshot(struct btrfs_pending_snapshot *pending,
 	struct btrfs_root *root = pending->root;
 	struct reloc_control *rc = root->fs_info->reloc_ctl;
 
-	if (!root->reloc_root || !rc)
+	if (!rc || !have_reloc_root(root))
 		return;
 
 	if (!rc->merge_reloc_tree)
@@ -4752,7 +4805,7 @@ int btrfs_reloc_post_snapshot(struct btrfs_trans_handle *trans,
 	struct reloc_control *rc = root->fs_info->reloc_ctl;
 	int ret;
 
-	if (!root->reloc_root || !rc)
+	if (!rc || !have_reloc_root(root))
 		return 0;
 
 	rc = root->fs_info->reloc_ctl;