On Wed, Feb 20, 2019 at 05:18:48PM +0800, Gao Xiang wrote: > commit 51232df5e4b268936beccde5248f312a316800be upstream. > > 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@xxxxxxxxxx> > Signed-off-by: Gao Xiang <gaoxiang25@xxxxxxxxxx> > Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> > Signed-off-by: Gao Xiang <gaoxiang25@xxxxxxxxxx> > > Conflicts: > drivers/staging/erofs/utils.c > Updates: > include/linux/xarray.h: > add xa_untag_pointer,xa_tag_pointer,xa_pointer_tag > from upstream 3159f943aafd in order to reduce > conflicts. No, sorry, I don't want to add xarray.h to 4.19.y, that's crazy. And even if we did, you do not slip it in as part of a different patch, it should come in as its own patch, with the same git commit id that it landed in 4.20 with. Please fix this up... greg k-h
