On Thu, Nov 14, 2019 at 10:10:03PM +0300, Dan Carpenter wrote:
> fs/erofs/zdata.c:443 z_erofs_register_collection()
> error: double unlocked 'cl->lock' (orig line 439)
>
> fs/erofs/zdata.c
> 432 cl = z_erofs_primarycollection(pcl);
> 433 cl->pageofs = map->m_la & ~PAGE_MASK;
> 434
> 435 /*
> 436 * lock all primary followed works before visible to others
> 437 * and mutex_trylock *never* fails for a new pcluster.
> 438 */
> 439 mutex_trylock(&cl->lock);
> ^^^^^^^^^^^^^^^^^^^^^^^^
> 440
> 441 err = erofs_register_workgroup(inode->i_sb, &pcl->obj, 0);
> 442 if (err) {
> 443 mutex_unlock(&cl->lock);
> ^^^^^^^^^^^^^^^^^^^^^^^
> How can we unlock if we don't know that the trylock succeeded?
The comment says it'll always succeed. That said, this is an uncommon
pattern -- usually we just mutex_lock(). If there's a good reason to use
mutex_trylock() instead, then I'd prefer it to be guarded with a BUG_ON.
