[PATCH for-4.19 06/12] staging: erofs: fix race when the managed cache is enabled

[Greg Kroah-Hartman]

On Mon, Feb 25, 2019 at 07:25:48AM -0800, Matthew Wilcox wrote:
> On Mon, Feb 25, 2019 at 04:04:49PM +0100, Greg Kroah-Hartman wrote:
> > On Wed, Feb 20, 2019 at 05:18:48PM +0800, Gao Xiang wrote:
> > > commit 51232df5e4b268936beccde5248f312a316800be upstream.
> > > 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.
> 
> I gave this a quick look when it came past, and I don't particularly
> object to this piece going into 4.19.y.  A full-on backport of XArray
> to 4.19 will be ... interesting, but essentially this is just some
> boilerplate.
> 
> > 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.
> 
> Putting in all of 3159f943aafdbacb2f94c38fdaadabf2bbde2a14 would be a
> bad idea; it actually ended up breaking m68k in a rather unexpected way
> which required 66ee620f06f99d72475db6eb638559ba608c7dee, which in turn
> caused a memory consumption regression ...

Where did the chain of regressions stop?  that would be good to know as
we will have to deal with this over time :)

thanks,

greg k-h