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btrfs: print-tree: Add eb locking status output for debug build

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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 <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ update comment ]
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Qu Wenruo 2018-04-24 13:03:13 +08:00 committed by David Sterba
parent 833aae18fc
commit b545993694
1 changed files with 21 additions and 0 deletions
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21
fs/btrfs/print-tree.c
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@ -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",