mm/memcontrol.c: cleanup some useless code

Compound pages handling in mem_cgroup_migrate is more convoluted than
necessary.  The state is duplicated in compound variable and the same
could be achieved by PageTransHuge check which is trivial and
hpage_nr_pages is already PageTransHuge aware.

It is much simpler to just use hpage_nr_pages for nr_pages and replace
the local variable by PageTransHuge check directly

Link: http://lkml.kernel.org/r/20191210160450.3395-1-pilgrimtao@gmail.com
Signed-off-by: Kaitao Cheng <pilgrimtao@gmail.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 27c231b..6f6dc87 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -6633,7 +6633,6 @@ void mem_cgroup_migrate(struct page *oldpage, struct page *newpage)
 {
        struct mem_cgroup *memcg;
        unsigned int nr_pages;
-       bool compound;
        unsigned long flags;
 
        VM_BUG_ON_PAGE(!PageLocked(oldpage), oldpage);
@@ -6655,8 +6654,7 @@ void mem_cgroup_migrate(struct page *oldpage, struct page *newpage)
                return;
 
        /* Force-charge the new page. The old one will be freed soon */
-       compound = PageTransHuge(newpage);
-       nr_pages = compound ? hpage_nr_pages(newpage) : 1;
+       nr_pages = hpage_nr_pages(newpage);
 
        page_counter_charge(&memcg->memory, nr_pages);
        if (do_memsw_account())
@@ -6666,7 +6664,8 @@ void mem_cgroup_migrate(struct page *oldpage, struct page *newpage)
        commit_charge(newpage, memcg, false);
 
        local_irq_save(flags);
-       mem_cgroup_charge_statistics(memcg, newpage, compound, nr_pages);
+       mem_cgroup_charge_statistics(memcg, newpage, PageTransHuge(newpage),
+                       nr_pages);
        memcg_check_events(memcg, newpage);
        local_irq_restore(flags);
 }