Merge branch 'writeback-workqueue' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq into for-3.10/core

Tejun writes:

-----

This is the pull request for the earlier patchset[1] with the same
name.  It's only three patches (the first one was committed to
workqueue tree) but the merge strategy is a bit involved due to the
dependencies.

* Because the conversion needs features from wq/for-3.10,
  block/for-3.10/core is based on rc3, and wq/for-3.10 has conflicts
  with rc3, I pulled mainline (rc5) into wq/for-3.10 to prevent those
  workqueue conflicts from flaring up in block tree.

* Resolving the issue that Jan and Dave raised about debugging
  requires arch-wide changes.  The patchset is being worked on[2] but
  it'll have to go through -mm after these changes show up in -next,
  and not included in this pull request.

The three commits are located in the following git branch.

  git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq.git writeback-workqueue

Pulling it into block/for-3.10/core produces a conflict in
drivers/md/raid5.c between the following two commits.

  e3620a3ad5 ("MD RAID5: Avoid accessing gendisk or queue structs when not available")
  2f6db2a707 ("raid5: use bio_reset()")

The conflict is trivial - one removes an "if ()" conditional while the
other removes "rbi->bi_next = NULL" right above it.  We just need to
remove both.  The merged branch is available at

  git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq.git block-test-merge

so that you can use it for verification.  The test merge commit has
proper merge description.

While these changes are a bit of pain to route, they make code simpler
and even have, while minute, measureable performance gain[3] even on a
workload which isn't particularly favorable to showing the benefits of
this conversion.

----

Fixed up the conflict.

Conflicts:
	drivers/md/raid5.c

Signed-off-by: Jens Axboe <axboe@kernel.dk>

6 files changed, 50 insertions, 250 deletions

diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 41733c5dc820..502517492258 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -31,13 +31,14 @@ EXPORT_SYMBOL_GPL(noop_backing_dev_info);
 static struct class *bdi_class;
 
 /*
- * bdi_lock protects updates to bdi_list and bdi_pending_list, as well as
- * reader side protection for bdi_pending_list. bdi_list has RCU reader side
+ * bdi_lock protects updates to bdi_list. bdi_list has RCU reader side
  * locking.
  */
 DEFINE_SPINLOCK(bdi_lock);
 LIST_HEAD(bdi_list);
-LIST_HEAD(bdi_pending_list);
+
+/* bdi_wq serves all asynchronous writeback tasks */
+struct workqueue_struct *bdi_wq;
 
 void bdi_lock_two(struct bdi_writeback *wb1, struct bdi_writeback *wb2)
 {
@@ -257,6 +258,11 @@ static int __init default_bdi_init(void)
 {
         int err;
 
+        bdi_wq = alloc_workqueue("writeback", WQ_MEM_RECLAIM | WQ_FREEZABLE |
+                                              WQ_UNBOUND | WQ_SYSFS, 0);
+        if (!bdi_wq)
+                return -ENOMEM;
+
         err = bdi_init(&default_backing_dev_info);
         if (!err)
                 bdi_register(&default_backing_dev_info, NULL, "default");
@@ -271,26 +277,6 @@ int bdi_has_dirty_io(struct backing_dev_info *bdi)
         return wb_has_dirty_io(&bdi->wb);
 }
 
-static void wakeup_timer_fn(unsigned long data)
-{
-        struct backing_dev_info *bdi = (struct backing_dev_info *)data;
-
-        spin_lock_bh(&bdi->wb_lock);
-        if (bdi->wb.task) {
-                trace_writeback_wake_thread(bdi);
-                wake_up_process(bdi->wb.task);
-        } else if (bdi->dev) {
-                /*
-                 * When bdi tasks are inactive for long time, they are killed.
-                 * In this case we have to wake-up the forker thread which
-                 * should create and run the bdi thread.
-                 */
-                trace_writeback_wake_forker_thread(bdi);
-                wake_up_process(default_backing_dev_info.wb.task);
-        }
-        spin_unlock_bh(&bdi->wb_lock);
-}
-
 /*
  * This function is used when the first inode for this bdi is marked dirty. It
  * wakes-up the corresponding bdi thread which should then take care of the
@@ -307,176 +293,7 @@ void bdi_wakeup_thread_delayed(struct backing_dev_info *bdi)
         unsigned long timeout;
 
         timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
-        mod_timer(&bdi->wb.wakeup_timer, jiffies + timeout);
-}
-
-/*
- * Calculate the longest interval (jiffies) bdi threads are allowed to be
- * inactive.
- */
-static unsigned long bdi_longest_inactive(void)
-{
-        unsigned long interval;
-
-        interval = msecs_to_jiffies(dirty_writeback_interval * 10);
-        return max(5UL * 60 * HZ, interval);
-}
-
-/*
- * Clear pending bit and wakeup anybody waiting for flusher thread creation or
- * shutdown
- */
-static void bdi_clear_pending(struct backing_dev_info *bdi)
-{
-        clear_bit(BDI_pending, &bdi->state);
-        smp_mb__after_clear_bit();
-        wake_up_bit(&bdi->state, BDI_pending);
-}
-
-static int bdi_forker_thread(void *ptr)
-{
-        struct bdi_writeback *me = ptr;
-
-        current->flags |= PF_SWAPWRITE;
-        set_freezable();
-
-        /*
-         * Our parent may run at a different priority, just set us to normal
-         */
-        set_user_nice(current, 0);
-
-        for (;;) {
-                struct task_struct *task = NULL;
-                struct backing_dev_info *bdi;
-                enum {
-                        NO_ACTION,   /* Nothing to do */
-                        FORK_THREAD, /* Fork bdi thread */
-                        KILL_THREAD, /* Kill inactive bdi thread */
-                } action = NO_ACTION;
-
-                /*
-                 * Temporary measure, we want to make sure we don't see
-                 * dirty data on the default backing_dev_info
-                 */
-                if (wb_has_dirty_io(me) || !list_empty(&me->bdi->work_list)) {
-                        del_timer(&me->wakeup_timer);
-                        wb_do_writeback(me, 0);
-                }
-
-                spin_lock_bh(&bdi_lock);
-                /*
-                 * In the following loop we are going to check whether we have
-                 * some work to do without any synchronization with tasks
-                 * waking us up to do work for them. Set the task state here
-                 * so that we don't miss wakeups after verifying conditions.
-                 */
-                set_current_state(TASK_INTERRUPTIBLE);
-
-                list_for_each_entry(bdi, &bdi_list, bdi_list) {
-                        bool have_dirty_io;
-
-                        if (!bdi_cap_writeback_dirty(bdi) ||
-                             bdi_cap_flush_forker(bdi))
-                                continue;
-
-                        WARN(!test_bit(BDI_registered, &bdi->state),
-                             "bdi %p/%s is not registered!\n", bdi, bdi->name);
-
-                        have_dirty_io = !list_empty(&bdi->work_list) ||
-                                        wb_has_dirty_io(&bdi->wb);
-
-                        /*
-                         * If the bdi has work to do, but the thread does not
-                         * exist - create it.
-                         */
-                        if (!bdi->wb.task && have_dirty_io) {
-                                /*
-                                 * Set the pending bit - if someone will try to
-                                 * unregister this bdi - it'll wait on this bit.
-                                 */
-                                set_bit(BDI_pending, &bdi->state);
-                                action = FORK_THREAD;
-                                break;
-                        }
-
-                        spin_lock(&bdi->wb_lock);
-
-                        /*
-                         * If there is no work to do and the bdi thread was
-                         * inactive long enough - kill it. The wb_lock is taken
-                         * to make sure no-one adds more work to this bdi and
-                         * wakes the bdi thread up.
-                         */
-                        if (bdi->wb.task && !have_dirty_io &&
-                            time_after(jiffies, bdi->wb.last_active +
-                                                bdi_longest_inactive())) {
-                                task = bdi->wb.task;
-                                bdi->wb.task = NULL;
-                                spin_unlock(&bdi->wb_lock);
-                                set_bit(BDI_pending, &bdi->state);
-                                action = KILL_THREAD;
-                                break;
-                        }
-                        spin_unlock(&bdi->wb_lock);
-                }
-                spin_unlock_bh(&bdi_lock);
-
-                /* Keep working if default bdi still has things to do */
-                if (!list_empty(&me->bdi->work_list))
-                        __set_current_state(TASK_RUNNING);
-
-                switch (action) {
-                case FORK_THREAD:
-                        __set_current_state(TASK_RUNNING);
-                        task = kthread_create(bdi_writeback_thread, &bdi->wb,
-                                              "flush-%s", dev_name(bdi->dev));
-                        if (IS_ERR(task)) {
-                                /*
-                                 * If thread creation fails, force writeout of
-                                 * the bdi from the thread. Hopefully 1024 is
-                                 * large enough for efficient IO.
-                                 */
-                                writeback_inodes_wb(&bdi->wb, 1024,
-                                                    WB_REASON_FORKER_THREAD);
-                        } else {
-                                /*
-                                 * The spinlock makes sure we do not lose
-                                 * wake-ups when racing with 'bdi_queue_work()'.
-                                 * And as soon as the bdi thread is visible, we
-                                 * can start it.
-                                 */
-                                spin_lock_bh(&bdi->wb_lock);
-                                bdi->wb.task = task;
-                                spin_unlock_bh(&bdi->wb_lock);
-                                wake_up_process(task);
-                        }
-                        bdi_clear_pending(bdi);
-                        break;
-
-                case KILL_THREAD:
-                        __set_current_state(TASK_RUNNING);
-                        kthread_stop(task);
-                        bdi_clear_pending(bdi);
-                        break;
-
-                case NO_ACTION:
-                        if (!wb_has_dirty_io(me) || !dirty_writeback_interval)
-                                /*
-                                 * There are no dirty data. The only thing we
-                                 * should now care about is checking for
-                                 * inactive bdi threads and killing them. Thus,
-                                 * let's sleep for longer time, save energy and
-                                 * be friendly for battery-driven devices.
-                                 */
-                                schedule_timeout(bdi_longest_inactive());
-                        else
-                                schedule_timeout(msecs_to_jiffies(dirty_writeback_interval * 10));
-                        try_to_freeze();
-                        break;
-                }
-        }
-
-        return 0;
+        mod_delayed_work(bdi_wq, &bdi->wb.dwork, timeout);
 }
 
 /*
@@ -489,6 +306,9 @@ static void bdi_remove_from_list(struct backing_dev_info *bdi)
         spin_unlock_bh(&bdi_lock);
 
         synchronize_rcu_expedited();
+
+        /* bdi_list is now unused, clear it to mark @bdi dying */
+        INIT_LIST_HEAD(&bdi->bdi_list);
 }
 
 int bdi_register(struct backing_dev_info *bdi, struct device *parent,
@@ -508,20 +328,6 @@ int bdi_register(struct backing_dev_info *bdi, struct device *parent,
 
         bdi->dev = dev;
 
-        /*
-         * Just start the forker thread for our default backing_dev_info,
-         * and add other bdi's to the list. They will get a thread created
-         * on-demand when they need it.
-         */
-        if (bdi_cap_flush_forker(bdi)) {
-                struct bdi_writeback *wb = &bdi->wb;
-
-                wb->task = kthread_run(bdi_forker_thread, wb, "bdi-%s",
-                                                dev_name(dev));
-                if (IS_ERR(wb->task))
-                        return PTR_ERR(wb->task);
-        }
-
         bdi_debug_register(bdi, dev_name(dev));
         set_bit(BDI_registered, &bdi->state);
 
@@ -545,8 +351,6 @@ EXPORT_SYMBOL(bdi_register_dev);
  */
 static void bdi_wb_shutdown(struct backing_dev_info *bdi)
 {
-        struct task_struct *task;
-
         if (!bdi_cap_writeback_dirty(bdi))
                 return;
 
@@ -556,22 +360,20 @@ static void bdi_wb_shutdown(struct backing_dev_info *bdi)
         bdi_remove_from_list(bdi);
 
         /*
-         * If setup is pending, wait for that to complete first
+         * Drain work list and shutdown the delayed_work.  At this point,
+         * @bdi->bdi_list is empty telling bdi_Writeback_workfn() that @bdi
+         * is dying and its work_list needs to be drained no matter what.
          */
-        wait_on_bit(&bdi->state, BDI_pending, bdi_sched_wait,
-                        TASK_UNINTERRUPTIBLE);
+        mod_delayed_work(bdi_wq, &bdi->wb.dwork, 0);
+        flush_delayed_work(&bdi->wb.dwork);
+        WARN_ON(!list_empty(&bdi->work_list));
 
         /*
-         * Finally, kill the kernel thread. We don't need to be RCU
-         * safe anymore, since the bdi is gone from visibility.
+         * This shouldn't be necessary unless @bdi for some reason has
+         * unflushed dirty IO after work_list is drained.  Do it anyway
+         * just in case.
          */
-        spin_lock_bh(&bdi->wb_lock);
-        task = bdi->wb.task;
-        bdi->wb.task = NULL;
-        spin_unlock_bh(&bdi->wb_lock);
-
-        if (task)
-                kthread_stop(task);
+        cancel_delayed_work_sync(&bdi->wb.dwork);
 }
 
 /*
@@ -597,10 +399,8 @@ void bdi_unregister(struct backing_dev_info *bdi)
                 bdi_set_min_ratio(bdi, 0);
                 trace_writeback_bdi_unregister(bdi);
                 bdi_prune_sb(bdi);
-                del_timer_sync(&bdi->wb.wakeup_timer);
 
-                if (!bdi_cap_flush_forker(bdi))
-                        bdi_wb_shutdown(bdi);
+                bdi_wb_shutdown(bdi);
                 bdi_debug_unregister(bdi);
 
                 spin_lock_bh(&bdi->wb_lock);
@@ -622,7 +422,7 @@ static void bdi_wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi)
         INIT_LIST_HEAD(&wb->b_io);
         INIT_LIST_HEAD(&wb->b_more_io);
         spin_lock_init(&wb->list_lock);
-        setup_timer(&wb->wakeup_timer, wakeup_timer_fn, (unsigned long)bdi);
+        INIT_DELAYED_WORK(&wb->dwork, bdi_writeback_workfn);
 }
 
 /*
@@ -695,12 +495,11 @@ void bdi_destroy(struct backing_dev_info *bdi)
         bdi_unregister(bdi);
 
         /*
-         * If bdi_unregister() had already been called earlier, the
-         * wakeup_timer could still be armed because bdi_prune_sb()
-         * can race with the bdi_wakeup_thread_delayed() calls from
-         * __mark_inode_dirty().
+         * If bdi_unregister() had already been called earlier, the dwork
+         * could still be pending because bdi_prune_sb() can race with the
+         * bdi_wakeup_thread_delayed() calls from __mark_inode_dirty().
          */
-        del_timer_sync(&bdi->wb.wakeup_timer);
+        cancel_delayed_work_sync(&bdi->wb.dwork);
 
         for (i = 0; i < NR_BDI_STAT_ITEMS; i++)
                 percpu_counter_destroy(&bdi->bdi_stat[i]);
diff --git a/mm/fremap.c b/mm/fremap.c
index 4723ac8d2fc2..87da3590c61e 100644
--- a/mm/fremap.c
+++ b/mm/fremap.c
@@ -204,10 +204,8 @@ get_write_lock:
                         unsigned long addr;
                         struct file *file = get_file(vma->vm_file);
 
-                        vm_flags = vma->vm_flags;
-                        if (!(flags & MAP_NONBLOCK))
-                                vm_flags |= VM_POPULATE;
-                        addr = mmap_region(file, start, size, vm_flags, pgoff);
+                        addr = mmap_region(file, start, size,
+                                        vma->vm_flags, pgoff);
                         fput(file);
                         if (IS_ERR_VALUE(addr)) {
                                 err = addr;
@@ -226,12 +224,6 @@ get_write_lock:
                 mutex_unlock(&mapping->i_mmap_mutex);
         }
 
-        if (!(flags & MAP_NONBLOCK) && !(vma->vm_flags & VM_POPULATE)) {
-                if (!has_write_lock)
-                        goto get_write_lock;
-                vma->vm_flags |= VM_POPULATE;
-        }
-
         if (vma->vm_flags & VM_LOCKED) {
                 /*
                  * drop PG_Mlocked flag for over-mapped range
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 0a0be33bb199..ca9a7c6d7e97 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2124,8 +2124,12 @@ int hugetlb_report_node_meminfo(int nid, char *buf)
 /* Return the number pages of memory we physically have, in PAGE_SIZE units. */
 unsigned long hugetlb_total_pages(void)
 {
-        struct hstate *h = &default_hstate;
-        return h->nr_huge_pages * pages_per_huge_page(h);
+        struct hstate *h;
+        unsigned long nr_total_pages = 0;
+
+        for_each_hstate(h)
+                nr_total_pages += h->nr_huge_pages * pages_per_huge_page(h);
+        return nr_total_pages;
 }
 
 static int hugetlb_acct_memory(struct hstate *h, long delta)
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 9597eec8239d..ee3765760818 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1779,7 +1779,11 @@ void try_offline_node(int nid)
         for (i = 0; i < MAX_NR_ZONES; i++) {
                 struct zone *zone = pgdat->node_zones + i;
 
-                if (zone->wait_table)
+                /*
+                 * wait_table may be allocated from boot memory,
+                 * here only free if it's allocated by vmalloc.
+                 */
+                if (is_vmalloc_addr(zone->wait_table))
                         vfree(zone->wait_table);
         }
 
diff --git a/mm/mlock.c b/mm/mlock.c
index 1c5e33fce639..79b7cf7d1bca 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -358,7 +358,7 @@ static int do_mlock(unsigned long start, size_t len, int on)
 
                 newflags = vma->vm_flags & ~VM_LOCKED;
                 if (on)
-                        newflags |= VM_LOCKED | VM_POPULATE;
+                        newflags |= VM_LOCKED;
 
                 tmp = vma->vm_end;
                 if (tmp > end)
@@ -418,8 +418,7 @@ int __mm_populate(unsigned long start, unsigned long len, int ignore_errors)
                  * range with the first VMA. Also, skip undesirable VMA types.
                  */
                 nend = min(end, vma->vm_end);
-                if ((vma->vm_flags & (VM_IO | VM_PFNMAP | VM_POPULATE)) !=
-                    VM_POPULATE)
+                if (vma->vm_flags & (VM_IO | VM_PFNMAP))
                         continue;
                 if (nstart < vma->vm_start)
                         nstart = vma->vm_start;
@@ -492,9 +491,9 @@ static int do_mlockall(int flags)
         struct vm_area_struct * vma, * prev = NULL;
 
         if (flags & MCL_FUTURE)
-                current->mm->def_flags |= VM_LOCKED | VM_POPULATE;
+                current->mm->def_flags |= VM_LOCKED;
         else
-                current->mm->def_flags &= ~(VM_LOCKED | VM_POPULATE);
+                current->mm->def_flags &= ~VM_LOCKED;
         if (flags == MCL_FUTURE)
                 goto out;
 
@@ -503,7 +502,7 @@ static int do_mlockall(int flags)
 
                 newflags = vma->vm_flags & ~VM_LOCKED;
                 if (flags & MCL_CURRENT)
-                        newflags |= VM_LOCKED | VM_POPULATE;
+                        newflags |= VM_LOCKED;
 
                 /* Ignore errors */
                 mlock_fixup(vma, &prev, vma->vm_start, vma->vm_end, newflags);
diff --git a/mm/mmap.c b/mm/mmap.c
index 2664a47cec93..6466699b16cb 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1306,7 +1306,9 @@ unsigned long do_mmap_pgoff(struct file *file, unsigned long addr,
         }
 
         addr = mmap_region(file, addr, len, vm_flags, pgoff);
-        if (!IS_ERR_VALUE(addr) && (vm_flags & VM_POPULATE))
+        if (!IS_ERR_VALUE(addr) &&
+            ((vm_flags & VM_LOCKED) ||
+             (flags & (MAP_POPULATE | MAP_NONBLOCK)) == MAP_POPULATE))
                 *populate = len;
         return addr;
 }