From: Gao Xiang Date: Thu, 22 Nov 2018 17:21:47 +0000 (+0800) Subject: staging: erofs: locked before registering for all new workgroups X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=23edf3abe7abb1d1ab856c893629b96209473a5b;p=openwrt%2Fstaging%2Fblogic.git staging: erofs: locked before registering for all new workgroups Let's make sure that the one registering a workgroup will also take the primary work lock at first for two reasons: 1) There's no need to introduce such a race window (and consequently overhead) between registering and locking, other tasks could break in by chance, and the race seems unnecessary (no benefit at all); 2) It's better to take the primary work when a workgroup is registered to apply the cache managed policy, for example, if some other tasks break in, it could turn into the in-place decompression rather than use as the cached decompression. Reviewed-by: Chao Yu Signed-off-by: Gao Xiang Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/staging/erofs/unzip_vle.c b/drivers/staging/erofs/unzip_vle.c index 4e5843e8ee35..6aa3c989dd4e 100644 --- a/drivers/staging/erofs/unzip_vle.c +++ b/drivers/staging/erofs/unzip_vle.c @@ -420,18 +420,23 @@ z_erofs_vle_work_register(const struct z_erofs_vle_work_finder *f, work = z_erofs_vle_grab_primary_work(grp); work->pageofs = f->pageofs; + /* + * lock all primary followed works before visible to others + * and mutex_trylock *never* fails for a new workgroup. + */ + mutex_trylock(&work->lock); + if (gnew) { int err = erofs_register_workgroup(f->sb, &grp->obj, 0); if (err) { + mutex_unlock(&work->lock); kmem_cache_free(z_erofs_workgroup_cachep, grp); return ERR_PTR(-EAGAIN); } } *f->owned_head = *f->grp_ret = grp; - - mutex_lock(&work->lock); return work; }