Re: [PATCH] zram: Avoid duplicate slots in batched writeback

[Andrew Morton <akpm@linux-foundation.org>]

On Tue, 10 Nov 2026 15:40:13 +0900 Sergey Senozhatsky <senozhatsky@chromium.org> wrote:

> On (26/11/10 14:18), raoxu wrote:
> > The writeback interface accepts multiple page_index and page_indexes
> > parameters in one operation. Their ranges can overlap, but
> > scan_slots_for_writeback() only excludes slots that are already being
> > written back or marked as same-filled.
> > 
> > A slot selected by an earlier range is placed on the post-processing list
> > and marked with ZRAM_PP_SLOT. Without checking that flag, an overlapping
> > range can enqueue the same slot again and submit it for writeback more
> > than once.
> > 
> > Skip slots already marked ZRAM_PP_SLOT while holding the slot lock. This
> > keeps each slot in a writeback scan session represented by at most one
> > post-processing entry and leaves the existing release and reuse paths
> > unchanged.
> > 
> > Signed-off-by: Xu Rao <raoxu@uniontech.com>
> 
> LGTM.
> Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
> 
> Jens, do you want to pick it up and route via block tree or should
> we route via "more traditional" tree (Andrew's tree)?

I grabbed it.

I did recently attempt to pull zram out of the mm project, by moving it
from mm.git's mm-unstable branch and into mm.git's mm-nonmm-unstable
branch.  Because "why does the mm project contain a block device
driver".

I undid that change after about a week - it didn't work out because
zram is joined at the hip with mm/zsmalloc.c.  zsmalloc is also used by
mm/zswap.c.

Oh well.  afaik the zram story has been going smoothly for a long
time(?).