From 6008859b6c6ea0991f530b125132174893903e3b Mon Sep 17 00:00:00 2001 From: Filipe Manana Date: Wed, 4 Oct 2023 11:38:49 +0100 Subject: btrfs: add and use helpers for reading and writing log_transid Currently the log_transid field of a root is always modified while holding the root's log_mutex locked. Most readers of a root's log_transid are also holding the root's log_mutex locked, however there is one exception which is btrfs_set_inode_last_trans() where we don't take the lock to avoid blocking several operations if log syncing is happening in parallel. Any races here should be harmless, and in the worst case they may cause a fsync to log an inode when it's not really needed, so nothing bad from a functional perspective. To avoid data race warnings from tools like KCSAN and other issues such as load and store tearing (amongst others, see [1]), create helpers to access the log_transid field of a root using READ_ONCE() and WRITE_ONCE(), and use these helpers where needed. [1] https://lwn.net/Articles/793253/ Signed-off-by: Filipe Manana Reviewed-by: David Sterba Signed-off-by: David Sterba --- fs/btrfs/tree-log.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'fs/btrfs/tree-log.c') diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c index 28a61a7dd371..958bb23d3d99 100644 --- a/fs/btrfs/tree-log.c +++ b/fs/btrfs/tree-log.c @@ -2958,7 +2958,7 @@ int btrfs_sync_log(struct btrfs_trans_handle *trans, btrfs_set_root_node(&log->root_item, log->node); memcpy(&new_root_item, &log->root_item, sizeof(new_root_item)); - root->log_transid++; + btrfs_set_root_log_transid(root, root->log_transid + 1); log->log_transid = root->log_transid; root->log_start_pid = 0; /* -- cgit