AuxXxilium/linux_dsm_epyc7002
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staging: erofs: locked before registering for all new workgroups

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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 <yuchao0@huawei.com>
Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Gao Xiang 2018-11-23 01:21:47 +08:00 committed by Greg Kroah-Hartman
parent 48d4bf3b05
commit 23edf3abe7
1 changed files with 7 additions and 2 deletions
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9
drivers/staging/erofs/unzip_vle.c
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@ -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;
}