btrfs: fix races on root_log_ctx lists

btrfs_remove_all_log_ctxs takes a shortcut where it avoids walking the
list because it knows all of the waiters are patiently waiting for the
commit to finish.

But, there's a small race where btrfs_sync_log can remove itself from
the list if it finds a log commit is already done.  Also, it uses
list_del_init() to remove itself from the list, but there's no way to
know if btrfs_remove_all_log_ctxs has already run, so we don't know for
sure if it is safe to call list_del_init().

This gets rid of all the shortcuts for btrfs_remove_all_log_ctxs(), and
just calls it with the proper locking.

This is part two of the corruption fixed by cbd60aa7cd1.  I should have
done this in the first place, but convinced myself the optimizations were
safe.  A 12 hour run of dbench 2048 will eventually trigger a list debug
WARN_ON for the list_del_init() in btrfs_sync_log().

Fixes: d1433debe7f4346cf9fc0dafc71c3137d2a97bc4
Reported-by: Dave Jones <davej@codemonkey.org.uk>
cc: stable@vger.kernel.org # 3.15+
Signed-off-by: Chris Mason <clm@fb.com>

1 files changed, 0 insertions, 1 deletions

diff --git a/ifpps.c b/ifpps.c
index 5495ce9..f2becb5 100644
--- a/ifpps.c
+++ b/ifpps.c
@@ -471,7 +471,6 @@ static void stats_diff(struct ifstat *old, struct ifstat *new,
 	DIFF(rx_multi);
 
 	DIFF(tx_bytes);
-	DIFF(tx_bytes);
 	DIFF(tx_packets);
 	DIFF(tx_drops);
 	DIFF(tx_errors);