From: Henry Burns <henryburns@xxxxxxxxxx> commit 1a87aa03597efa9641e92875b883c94c7f872ccb upstream. 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. Link: http://lkml.kernel.org/r/20190809181751.219326-1-henryburns@xxxxxxxxxx Fixes: 48b4800a1c6a ("zsmalloc: page migration support") Signed-off-by: Henry Burns <henryburns@xxxxxxxxxx> Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx> Cc: Henry Burns <henrywolfeburns@xxxxxxxxx> Cc: Minchan Kim <minchan@xxxxxxxxxx> Cc: Shakeel Butt <shakeelb@xxxxxxxxxx> Cc: Jonathan Adams <jwadams@xxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- mm/zsmalloc.c | 19 +++++++++++++++---- 1 file changed, 15 insertions(+), 4 deletions(-) --- a/mm/zsmalloc.c +++ b/mm/zsmalloc.c @@ -1878,6 +1878,18 @@ static void dec_zspage_isolation(struct 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); + if (fg == ZS_EMPTY) + schedule_work(&pool->free_work); + +} + static void replace_sub_page(struct size_class *class, struct zspage *zspage, struct page *newpage, struct page *oldpage) { @@ -2047,7 +2059,7 @@ int zs_page_migrate(struct address_space * the list if @page is final isolated subpage in the zspage. */ if (!is_zspage_isolated(zspage)) - putback_zspage(class, zspage); + putback_zspage_deferred(pool, class, zspage); reset_page(page); put_page(page); @@ -2093,14 +2105,13 @@ void zs_page_putback(struct page *page) spin_lock(&class->lock); dec_zspage_isolation(zspage); if (!is_zspage_isolated(zspage)) { - fg = putback_zspage(class, zspage); /* * Due to page_lock, we cannot free zspage immediately * so let's defer. */ - if (fg == ZS_EMPTY) - schedule_work(&pool->free_work); + putback_zspage_deferred(pool, class, zspage); } + spin_unlock(&class->lock); }
