We currently rely too heavily on roots being read-only to save us from just accessing root->commit_root. We can easily balance blocks out from underneath a read only root, so to save us from getting screwed make sure we only access root->commit_root under the commit root sem. Thanks,
Signed-off-by: Josef Bacik <[email protected]> --- fs/btrfs/ctree.c | 6 ++++++ fs/btrfs/ctree.h | 1 + fs/btrfs/send.c | 1 + 3 files changed, 8 insertions(+) diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c index 71bbafe..0e9569c 100644 --- a/fs/btrfs/ctree.c +++ b/fs/btrfs/ctree.c @@ -2769,9 +2769,13 @@ again: * the commit roots are read only * so we always do read locks */ + if (p->need_commit_sem) + down_read(&root->fs_info->commit_root_sem); b = root->commit_root; extent_buffer_get(b); level = btrfs_header_level(b); + if (p->need_commit_sem) + up_read(&root->fs_info->commit_root_sem); if (!p->skip_locking) btrfs_tree_read_lock(b); } else { @@ -5436,6 +5440,7 @@ int btrfs_compare_trees(struct btrfs_root *left_root, * the right if possible or go up and right. */ + down_read(&left_root->fs_info->commit_root_sem); left_level = btrfs_header_level(left_root->commit_root); left_root_level = left_level; left_path->nodes[left_level] = left_root->commit_root; @@ -5445,6 +5450,7 @@ int btrfs_compare_trees(struct btrfs_root *left_root, right_root_level = right_level; right_path->nodes[right_level] = right_root->commit_root; extent_buffer_get(right_path->nodes[right_level]); + up_read(&left_root->fs_info->commit_root_sem); if (left_level == 0) btrfs_item_key_to_cpu(left_path->nodes[left_level], diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h index 2277006..453d859 100644 --- a/fs/btrfs/ctree.h +++ b/fs/btrfs/ctree.h @@ -609,6 +609,7 @@ struct btrfs_path { unsigned int skip_locking:1; unsigned int leave_spinning:1; unsigned int search_commit_root:1; + unsigned int need_commit_sem:1; }; /* diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c index 6f035ee..7e7552c 100644 --- a/fs/btrfs/send.c +++ b/fs/btrfs/send.c @@ -493,6 +493,7 @@ static struct btrfs_path *alloc_path_for_send(void) return NULL; path->search_commit_root = 1; path->skip_locking = 1; + path->need_commit_sem = 1; return path; } -- 1.8.3.1 -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
