staging: erofs: fix race when the managed cache is enabled

Browse source

When the managed cache is enabled, the last reference count
of a workgroup must be used for its workstation.

Otherwise, it could lead to incorrect (un)freezes in
the reclaim path, and it would be harmful.

A typical race as follows:

Thread 1 (In the reclaim path)  Thread 2
workgroup_freeze(grp, 1)                                refcnt = 1
...
workgroup_unfreeze(grp, 1)                              refcnt = 1
                                workgroup_get(grp)      refcnt = 2 (x)
workgroup_put(grp)                                      refcnt = 1 (x)
                                ...unexpected behaviors

* grp is detached but still used, which violates cache-managed
  freeze constraint.

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 01:16:00 +08:00 • committed by Greg Kroah-Hartman

parent eef1687898

commit 51232df5e4

2 changed files with 96 additions and 39 deletions

Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL

Download patch file Download diff file Expand all files Collapse all files

1

drivers/staging/erofs/internal.h

View file

134

drivers/staging/erofs/utils.c

View file