Revert "mm: memcontrol: fix NULL pointer crash in test_clear_page_writeback()" (5c95b531) · Commits · e / devices / android_kernel_fairphone_FP3

include/linux/memcontrol.h

+5 −28

Original line number	Diff line number	Diff line
		@@ -490,21 +490,9 @@ bool mem_cgroup_oom_synchronize(bool wait);
		extern int do_swap_account;
		#endif

		struct mem_cgroup lock_page_memcg(struct page page);
		void __unlock_page_memcg(struct mem_cgroup *memcg);
		void lock_page_memcg(struct page *page);
		void unlock_page_memcg(struct page *page);

		static inline void __mem_cgroup_update_page_stat(struct page *page,
		struct mem_cgroup *memcg,
		enum mem_cgroup_stat_index idx,
		int val)
		{
		VM_BUG_ON(!(rcu_read_lock_held() \|\| PageLocked(page)));

		if (memcg && memcg->stat)
		this_cpu_add(memcg->stat->count[idx], val);
		}

		/**
		* mem_cgroup_update_page_stat - update page state statistics
		* @page: the page
		@@ -520,12 +508,13 @@ static inline void __mem_cgroup_update_page_stat(struct page *page,
		* mem_cgroup_update_page_stat(page, state, -1);
		* unlock_page(page) or unlock_page_memcg(page)
		*/

		static inline void mem_cgroup_update_page_stat(struct page *page,
		enum mem_cgroup_stat_index idx, int val)
		{
		VM_BUG_ON(!(rcu_read_lock_held() \|\| PageLocked(page)));

		__mem_cgroup_update_page_stat(page, page->mem_cgroup, idx, val);
		if (page->mem_cgroup)
		this_cpu_add(page->mem_cgroup->stat->count[idx], val);
		}

		static inline void mem_cgroup_inc_page_stat(struct page *page,
		@@ -720,12 +709,7 @@ mem_cgroup_print_oom_info(struct mem_cgroup memcg, struct task_struct p)
		{
		}

		static inline struct mem_cgroup lock_page_memcg(struct page page)
		{
		return NULL;
		}

		static inline void __unlock_page_memcg(struct mem_cgroup *memcg)
		static inline void lock_page_memcg(struct page *page)
		{
		}

		@@ -761,13 +745,6 @@ static inline void mem_cgroup_update_page_stat(struct page *page,
		{
		}

		static inline void __mem_cgroup_update_page_stat(struct page *page,
		struct mem_cgroup *memcg,
		enum mem_cgroup_stat_index idx,
		int nr)
		{
		}

		static inline void mem_cgroup_inc_page_stat(struct page *page,
		enum mem_cgroup_stat_index idx)
		{

mm/memcontrol.c

+12 −31

Original line number	Diff line number	Diff line
		@@ -1619,13 +1619,9 @@ bool mem_cgroup_oom_synchronize(bool handle)
		* @page: the page
		*
		* This function protects unlocked LRU pages from being moved to
		* another cgroup.
		*
		* It ensures lifetime of the returned memcg. Caller is responsible
		* for the lifetime of the page; __unlock_page_memcg() is available
		* when @page might get freed inside the locked section.
		* another cgroup and stabilizes their page->mem_cgroup binding.
		*/
		struct mem_cgroup lock_page_memcg(struct page page)
		void lock_page_memcg(struct page *page)
		{
		struct mem_cgroup *memcg;
		unsigned long flags;
		@@ -1634,24 +1630,18 @@ struct mem_cgroup lock_page_memcg(struct page page)
		* The RCU lock is held throughout the transaction. The fast
		* path can get away without acquiring the memcg->move_lock
		* because page moving starts with an RCU grace period.
		*
		* The RCU lock also protects the memcg from being freed when
		* the page state that is going to change is the only thing
		* preventing the page itself from being freed. E.g. writeback
		* doesn't hold a page reference and relies on PG_writeback to
		* keep off truncation, migration and so forth.
		*/
		rcu_read_lock();

		if (mem_cgroup_disabled())
		return NULL;
		return;
		again:
		memcg = page->mem_cgroup;
		if (unlikely(!memcg))
		return NULL;
		return;

		if (atomic_read(&memcg->moving_account) <= 0)
		return memcg;
		return;

		spin_lock_irqsave(&memcg->move_lock, flags);
		if (memcg != page->mem_cgroup) {
		@@ -1667,18 +1657,18 @@ struct mem_cgroup lock_page_memcg(struct page page)
		memcg->move_lock_task = current;
		memcg->move_lock_flags = flags;

		return memcg;
		return;
		}
		EXPORT_SYMBOL(lock_page_memcg);

		/**
		* __unlock_page_memcg - unlock and unpin a memcg
		* @memcg: the memcg
		*
		* Unlock and unpin a memcg returned by lock_page_memcg().
		* unlock_page_memcg - unlock a page->mem_cgroup binding
		* @page: the page
		*/
		void __unlock_page_memcg(struct mem_cgroup *memcg)
		void unlock_page_memcg(struct page *page)
		{
		struct mem_cgroup *memcg = page->mem_cgroup;

		if (memcg && memcg->move_lock_task == current) {
		unsigned long flags = memcg->move_lock_flags;

		@@ -1690,15 +1680,6 @@ void __unlock_page_memcg(struct mem_cgroup *memcg)

		rcu_read_unlock();
		}

		/**
		* unlock_page_memcg - unlock a page->mem_cgroup binding
		* @page: the page
		*/
		void unlock_page_memcg(struct page *page)
		{
		__unlock_page_memcg(page->mem_cgroup);
		}
		EXPORT_SYMBOL(unlock_page_memcg);

		/*

mm/page-writeback.c

+3 −11

Original line number	Diff line number	Diff line
		@@ -2704,10 +2704,9 @@ EXPORT_SYMBOL(clear_page_dirty_for_io);
		int test_clear_page_writeback(struct page *page)
		{
		struct address_space *mapping = page_mapping(page);
		struct mem_cgroup *memcg;
		int ret;

		memcg = lock_page_memcg(page);
		lock_page_memcg(page);
		if (mapping && mapping_use_writeback_tags(mapping)) {
		struct inode *inode = mapping->host;
		struct backing_dev_info *bdi = inode_to_bdi(inode);
		@@ -2735,20 +2734,13 @@ int test_clear_page_writeback(struct page *page)
		} else {
		ret = TestClearPageWriteback(page);
		}
		/*
		* NOTE: Page might be free now! Writeback doesn't hold a page
		* reference on its own, it relies on truncation to wait for
		* the clearing of PG_writeback. The below can only access
		* page state that is static across allocation cycles.
		*/
		if (ret) {
		__mem_cgroup_update_page_stat(page, memcg,
		MEM_CGROUP_STAT_WRITEBACK, -1);
		mem_cgroup_dec_page_stat(page, MEM_CGROUP_STAT_WRITEBACK);
		dec_node_page_state(page, NR_WRITEBACK);
		dec_zone_page_state(page, NR_ZONE_WRITE_PENDING);
		inc_node_page_state(page, NR_WRITTEN);
		}
		__unlock_page_memcg(memcg);
		unlock_page_memcg(page);
		return ret;
		}