From b545993694a6e3bf6e801071df00e0ad47526bb8 Mon Sep 17 00:00:00 2001 From: Qu Wenruo Date: Tue, 24 Apr 2018 13:03:13 +0800 Subject: [PATCH] btrfs: print-tree: Add eb locking status output for debug build It's pretty handy if we can get the debug output for locking status of an extent buffer, specially for race condition related debugging. So add the following output for btrfs_print_tree() and btrfs_print_leaf(): - refs - write_locks (as w:%d) - read_locks (as r:%d) - blocking_writers (as bw:%d) - blocking_readers (as br:%d) - spinning_writers (as sw:%d) - spinning_readers (as sr:%d) - lock_owner - current->pid Signed-off-by: Qu Wenruo Reviewed-by: David Sterba [ update comment ] Signed-off-by: David Sterba --- fs/btrfs/print-tree.c | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) diff --git a/fs/btrfs/print-tree.c b/fs/btrfs/print-tree.c index 21a831d..a4e11cf 100644 --- a/fs/btrfs/print-tree.c +++ b/fs/btrfs/print-tree.c @@ -166,6 +166,25 @@ static void print_uuid_item(struct extent_buffer *l, unsigned long offset, } } +/* + * Helper to output refs and locking status of extent buffer. Useful to debug + * race condition related problems. + */ +static void print_eb_refs_lock(struct extent_buffer *eb) +{ +#ifdef CONFIG_BTRFS_DEBUG + btrfs_info(eb->fs_info, +"refs %u lock (w:%d r:%d bw:%d br:%d sw:%d sr:%d) lock_owner %u current %u", + atomic_read(&eb->refs), atomic_read(&eb->write_locks), + atomic_read(&eb->read_locks), + atomic_read(&eb->blocking_writers), + atomic_read(&eb->blocking_readers), + atomic_read(&eb->spinning_writers), + atomic_read(&eb->spinning_readers), + eb->lock_owner, current->pid); +#endif +} + void btrfs_print_leaf(struct extent_buffer *l) { struct btrfs_fs_info *fs_info; @@ -193,6 +212,7 @@ void btrfs_print_leaf(struct extent_buffer *l) "leaf %llu gen %llu total ptrs %d free space %d owner %llu", btrfs_header_bytenr(l), btrfs_header_generation(l), nr, btrfs_leaf_free_space(fs_info, l), btrfs_header_owner(l)); + print_eb_refs_lock(l); for (i = 0 ; i < nr ; i++) { item = btrfs_item_nr(i); btrfs_item_key_to_cpu(l, &key, i); @@ -347,6 +367,7 @@ void btrfs_print_tree(struct extent_buffer *c, bool follow) btrfs_header_bytenr(c), level, btrfs_header_generation(c), nr, (u32)BTRFS_NODEPTRS_PER_BLOCK(fs_info) - nr, btrfs_header_owner(c)); + print_eb_refs_lock(c); for (i = 0; i < nr; i++) { btrfs_node_key_to_cpu(c, &key, i); pr_info("\tkey %d (%llu %u %llu) block %llu gen %llu\n", -- 2.7.4