Re: [PATCH 1/2 v2] mm/zsmalloc.c: Migration can leave pages in ZS_EMPTY indefinitely

[Sergey Senozhatsky]

On (08/09/19 11:17), Henry Burns wrote:
> In zs_page_migrate() we call putback_zspage() after we have finished
> migrating all pages in this zspage. However, the return value is ignored.
> If a zs_free() races in between zs_page_isolate() and zs_page_migrate(),
> freeing the last object in the zspage, putback_zspage() will leave the page
> in ZS_EMPTY for potentially an unbounded amount of time.
> 
> To fix this, we need to do the same thing as zs_page_putback() does:
> schedule free_work to occur.  To avoid duplicated code, move the
> sequence to a new putback_zspage_deferred() function which both
> zs_page_migrate() and zs_page_putback() call.
> 
> Fixes: 48b4800a1c6a ("zsmalloc: page migration support")
> Signed-off-by: Henry Burns <henryburns@xxxxxxxxxx>

Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx>

+ Andrew

	-ss