On 2019/2/25 23:51, Greg Kroah-Hartman wrote: > On Mon, Feb 25, 2019 at 11:07:19PM +0800, Gao Xiang wrote: >> >> On 2019/2/25 23:04, Greg Kroah-Hartman wrote: >>> 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. >> Or can I define these xa_untag_pointer,xa_tag_pointer,xa_pointer_tag in >> a erofs header internally? it is acceptable? > No, that's not ok. > > If you want to backport a subset of the api, and Matthew agrees with it > (I think he did), then let's backport a subset, as a single patch, that > matches the original patch comments and git id. OK, I will backport a minimum subset of upstream 3159f943aafd only with xa_untag_pointer,xa_tag_pointer,xa_pointer_tag as the only valid part. I will do this soon and thanks Greg and Matthew for taking time on this patch :) Thanks, Gao Xiang > > thanks, > > greg k-h
