btrfs: Remove unnecessary check from join_running_log_trans
authorNikolay Borisov <nborisov@suse.com>
Thu, 23 May 2019 11:51:26 +0000 (14:51 +0300)
committerDavid Sterba <dsterba@suse.com>
Mon, 9 Sep 2019 12:59:02 +0000 (14:59 +0200)
commite678934cbe5f026c2765a1da651e61daa5724fb3
treee1070146d58367624b9ec65eb0ced82515958de5
parent32e534402ad52e9f35c32be68e25213db722892b
btrfs: Remove unnecessary check from join_running_log_trans

join_running_log_trans checks btrfs_root::log_root outside of
btrfs_root::log_mutex to avoid contention on the mutex. Turns out this
check is not necessary because the two callers of join_running_log_trans
(both of which deal with removing entries from the tree-log during
unlink) explicitly check whether the respective inode has been logged in
the current transaction.

If it hasn't then it won't have any items in the tree-log and call path
will return before calling join_running_log_trans. If the check passes,
however, then it's guaranteed that btrfs_root::log_root is set because
the inode is logged.

Those guarantees allows us to remove the speculative as well as the
implicity and tricky memory barrier.

Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
fs/btrfs/tree-log.c