Merge branch 'for-4.15/block' of git://git.kernel.dk/linux-block

Pull core block layer updates from Jens Axboe:
 "This is the main pull request for block storage for 4.15-rc1.

  Nothing out of the ordinary in here, and no API changes or anything
  like that. Just various new features for drivers, core changes, etc.
  In particular, this pull request contains:

   - A patch series from Bart, closing the whole on blk/scsi-mq queue
     quescing.

   - A series from Christoph, building towards hidden gendisks (for
     multipath) and ability to move bio chains around.

   - NVMe
        - Support for native multipath for NVMe (Christoph).
        - Userspace notifications for AENs (Keith).
        - Command side-effects support (Keith).
        - SGL support (Chaitanya Kulkarni)
        - FC fixes and improvements (James Smart)
        - Lots of fixes and tweaks (Various)

   - bcache
        - New maintainer (Michael Lyle)
        - Writeback control improvements (Michael)
        - Various fixes (Coly, Elena, Eric, Liang, et al)

   - lightnvm updates, mostly centered around the pblk interface
     (Javier, Hans, and Rakesh).

   - Removal of unused bio/bvec kmap atomic interfaces (me, Christoph)

   - Writeback series that fix the much discussed hundreds of millions
     of sync-all units. This goes all the way, as discussed previously
     (me).

   - Fix for missing wakeup on writeback timer adjustments (Yafang
     Shao).

   - Fix laptop mode on blk-mq (me).

   - {mq,name} tupple lookup for IO schedulers, allowing us to have
     alias names. This means you can use 'deadline' on both !mq and on
     mq (where it's called mq-deadline). (me).

   - blktrace race fix, oopsing on sg load (me).

   - blk-mq optimizations (me).

   - Obscure waitqueue race fix for kyber (Omar).

   - NBD fixes (Josef).

   - Disable writeback throttling by default on bfq, like we do on cfq
     (Luca Miccio).

   - Series from Ming that enable us to treat flush requests on blk-mq
     like any other request. This is a really nice cleanup.

   - Series from Ming that improves merging on blk-mq with schedulers,
     getting us closer to flipping the switch on scsi-mq again.

   - BFQ updates (Paolo).

   - blk-mq atomic flags memory ordering fixes (Peter Z).

   - Loop cgroup support (Shaohua).

   - Lots of minor fixes from lots of different folks, both for core and
     driver code"

* 'for-4.15/block' of git://git.kernel.dk/linux-block: (294 commits)
  nvme: fix visibility of "uuid" ns attribute
  blk-mq: fixup some comment typos and lengths
  ide: ide-atapi: fix compile error with defining macro DEBUG
  blk-mq: improve tag waiting setup for non-shared tags
  brd: remove unused brd_mutex
  blk-mq: only run the hardware queue if IO is pending
  block: avoid null pointer dereference on null disk
  fs: guard_bio_eod() needs to consider partitions
  xtensa/simdisk: fix compile error
  nvme: expose subsys attribute to sysfs
  nvme: create 'slaves' and 'holders' entries for hidden controllers
  block: create 'slaves' and 'holders' entries for hidden gendisks
  nvme: also expose the namespace identification sysfs files for mpath nodes
  nvme: implement multipath access to nvme subsystems
  nvme: track shared namespaces
  nvme: introduce a nvme_ns_ids structure
  nvme: track subsystems
  block, nvme: Introduce blk_mq_req_flags_t
  block, scsi: Make SCSI quiesce and resume work reliably
  block: Add the QUEUE_FLAG_PREEMPT_ONLY request queue flag
  ...

1 files changed, 18 insertions, 18 deletions

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 0b9c5cbe8eba..c518c845f202 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -1972,31 +1972,31 @@ bool wb_over_bg_thresh(struct bdi_writeback *wb)
 int dirty_writeback_centisecs_handler(struct ctl_table *table, int write,
         void __user *buffer, size_t *length, loff_t *ppos)
 {
-        proc_dointvec(table, write, buffer, length, ppos);
-        return 0;
+        unsigned int old_interval = dirty_writeback_interval;
+        int ret;
+
+        ret = proc_dointvec(table, write, buffer, length, ppos);
+
+        /*
+         * Writing 0 to dirty_writeback_interval will disable periodic writeback
+         * and a different non-zero value will wakeup the writeback threads.
+         * wb_wakeup_delayed() would be more appropriate, but it's a pain to
+         * iterate over all bdis and wbs.
+         * The reason we do this is to make the change take effect immediately.
+         */
+        if (!ret && write && dirty_writeback_interval &&
+                dirty_writeback_interval != old_interval)
+                wakeup_flusher_threads(WB_REASON_PERIODIC);
+
+        return ret;
 }
 
 #ifdef CONFIG_BLOCK
 void laptop_mode_timer_fn(unsigned long data)
 {
         struct request_queue *q = (struct request_queue *)data;
-        int nr_pages = global_node_page_state(NR_FILE_DIRTY) +
-                global_node_page_state(NR_UNSTABLE_NFS);
-        struct bdi_writeback *wb;
 
-        /*
-         * We want to write everything out, not just down to the dirty
-         * threshold
-         */
-        if (!bdi_has_dirty_io(q->backing_dev_info))
-                return;
-
-        rcu_read_lock();
-        list_for_each_entry_rcu(wb, &q->backing_dev_info->wb_list, bdi_node)
-                if (wb_has_dirty_io(wb))
-                        wb_start_writeback(wb, nr_pages, true,
-                                           WB_REASON_LAPTOP_TIMER);
-        rcu_read_unlock();
+        wakeup_flusher_threads_bdi(q->backing_dev_info, WB_REASON_LAPTOP_TIMER);
 }
 
 /*