Messages in this thread | | | Date | Mon, 5 Aug 2019 13:14:40 +0900 | From | Minchan Kim <> | Subject | Re: [PATCH 1/2] mm/zsmalloc.c: Migration can leave pages in ZS_EMPTY indefinitely |
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On Thu, Aug 01, 2019 at 06:53:31PM -0700, 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.
Nice catch.
> > 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. > > Signed-off-by: Henry Burns <henryburns@google.com> Cc: <stable@vger.kernel.org> [4.8+] Acked-by: Minchan Kim <minchan@kernel.org>
Below a just trivial:
> --- > mm/zsmalloc.c | 30 ++++++++++++++++++++---------- > 1 file changed, 20 insertions(+), 10 deletions(-) > > diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c > index 1cda3fe0c2d9..efa660a87787 100644 > --- a/mm/zsmalloc.c > +++ b/mm/zsmalloc.c > @@ -1901,6 +1901,22 @@ static void dec_zspage_isolation(struct zspage *zspage) > zspage->isolated--; > } > > +static void putback_zspage_deferred(struct zs_pool *pool, > + struct size_class *class, > + struct zspage *zspage) > +{ > + enum fullness_group fg; > + > + fg = putback_zspage(class, zspage); > + /* > + * Due to page_lock, we cannot free zspage immediately > + * so let's defer. > + */
Could you move this comment function's description since it becomes a function?
Thanks.
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