diff options
Diffstat (limited to 'fs/btrfs/tree-log.c')
| -rw-r--r-- | fs/btrfs/tree-log.c | 36 |
1 files changed, 27 insertions, 9 deletions
diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c index 29b82a795522..8a6cc600bf18 100644 --- a/fs/btrfs/tree-log.c +++ b/fs/btrfs/tree-log.c @@ -2932,7 +2932,8 @@ out: * in the tree of log roots */ static int update_log_root(struct btrfs_trans_handle *trans, - struct btrfs_root *log) + struct btrfs_root *log, + struct btrfs_root_item *root_item) { struct btrfs_fs_info *fs_info = log->fs_info; int ret; @@ -2940,10 +2941,10 @@ static int update_log_root(struct btrfs_trans_handle *trans, if (log->log_transid == 1) { /* insert root item on the first sync */ ret = btrfs_insert_root(trans, fs_info->log_root_tree, - &log->root_key, &log->root_item); + &log->root_key, root_item); } else { ret = btrfs_update_root(trans, fs_info->log_root_tree, - &log->root_key, &log->root_item); + &log->root_key, root_item); } return ret; } @@ -3041,6 +3042,7 @@ int btrfs_sync_log(struct btrfs_trans_handle *trans, struct btrfs_fs_info *fs_info = root->fs_info; struct btrfs_root *log = root->log_root; struct btrfs_root *log_root_tree = fs_info->log_root_tree; + struct btrfs_root_item new_root_item; int log_transid = 0; struct btrfs_log_ctx root_log_ctx; struct blk_plug plug; @@ -3104,18 +3106,26 @@ int btrfs_sync_log(struct btrfs_trans_handle *trans, goto out; } + /* + * We _must_ update under the root->log_mutex in order to make sure we + * have a consistent view of the log root we are trying to commit at + * this moment. + * + * We _must_ copy this into a local copy, because we are not holding the + * log_root_tree->log_mutex yet. This is important because when we + * commit the log_root_tree we must have a consistent view of the + * log_root_tree when we update the super block to point at the + * log_root_tree bytenr. If we update the log_root_tree here we'll race + * with the commit and possibly point at the new block which we may not + * have written out. + */ btrfs_set_root_node(&log->root_item, log->node); + memcpy(&new_root_item, &log->root_item, sizeof(new_root_item)); root->log_transid++; log->log_transid = root->log_transid; root->log_start_pid = 0; /* - * Update or create log root item under the root's log_mutex to prevent - * races with concurrent log syncs that can lead to failure to update - * log root item because it was not created yet. - */ - ret = update_log_root(trans, log); - /* * IO has been started, blocks of the log tree have WRITTEN flag set * in their headers. new modifications of the log will be written to * new positions. so it's safe to allow log writers to go in. @@ -3135,6 +3145,14 @@ int btrfs_sync_log(struct btrfs_trans_handle *trans, mutex_unlock(&log_root_tree->log_mutex); mutex_lock(&log_root_tree->log_mutex); + + /* + * Now we are safe to update the log_root_tree because we're under the + * log_mutex, and we're a current writer so we're holding the commit + * open until we drop the log_mutex. + */ + ret = update_log_root(trans, log, &new_root_item); + if (atomic_dec_and_test(&log_root_tree->log_writers)) { /* atomic_dec_and_test implies a barrier */ cond_wake_up_nomb(&log_root_tree->log_writer_wait); |