Merge branch 'for-4.7/core' of git://git.kernel.dk/linux-block

Pull core block layer updates from Jens Axboe:
 "This is the core block IO changes for this merge window.  Nothing
  earth shattering in here, it's mostly just fixes.  In detail:

   - Fix for a long standing issue where wrong ordering in blk-mq caused
     order_to_size() to spew a warning.  From Bart.

   - Async discard support from Christoph.  Basically just splitting our
     sync interface into a submit + wait part.

   - Add a cleaner interface for flagging whether a device has a write
     back cache or not.  We've previously overloaded blk_queue_flush()
     with this, but let's make it more explicit.  Drivers cleaned up and
     updated in the drivers pull request.  From me.

   - Fix for a double check for whether IO accounting is enabled or not.
     From Michael Callahan.

   - Fix for the async discard from Mike Snitzer, reinstating the early
     EOPNOTSUPP return if the device doesn't support discards.

   - Also from Mike, export bio_inc_remaining() so dm can drop it's
     private copy of it.

   - From Ming Lin, add support for passing in an offset for request
     payloads.

   - Tag function export from Sagi, which will be used in NVMe in the
     drivers pull.

   - Two blktrace related fixes from Shaohua.

   - Propagate NOMERGE flag when making a request from a bio, also from
     Shaohua.

   - An optimization to not parse cgroup paths in blk-throttle, if we
     don't need to.  From Shaohua"

* 'for-4.7/core' of git://git.kernel.dk/linux-block:
  blk-mq: fix undefined behaviour in order_to_size()
  blk-throttle: don't parse cgroup path if trace isn't enabled
  blktrace: add missed mask name
  blktrace: delete garbage for message trace
  block: make bio_inc_remaining() interface accessible again
  block: reinstate early return of -EOPNOTSUPP from blkdev_issue_discard
  block: Minor blk_account_io_start usage cleanup
  block: add __blkdev_issue_discard
  block: remove struct bio_batch
  block: copy NOMERGE flag from bio to request
  block: add ability to flag write back caching on a device
  blk-mq: Export tagset iter function
  block: add offset in blk_add_request_payload()
  writeback: Fix performance regression in wb_over_bg_thresh()

1 files changed, 26 insertions, 0 deletions

diff --git a/block/blk-settings.c b/block/blk-settings.c
index 331e4eee0dda..c903bee43cf8 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -846,6 +846,32 @@ void blk_queue_flush_queueable(struct request_queue *q, bool queueable)
 }
 EXPORT_SYMBOL_GPL(blk_queue_flush_queueable);
 
+/**
+ * blk_queue_write_cache - configure queue's write cache
+ * @q:		the request queue for the device
+ * @wc:		write back cache on or off
+ * @fua:	device supports FUA writes, if true
+ *
+ * Tell the block layer about the write cache of @q.
+ */
+void blk_queue_write_cache(struct request_queue *q, bool wc, bool fua)
+{
+	spin_lock_irq(q->queue_lock);
+	if (wc) {
+		queue_flag_set(QUEUE_FLAG_WC, q);
+		q->flush_flags = REQ_FLUSH;
+	} else
+		queue_flag_clear(QUEUE_FLAG_WC, q);
+	if (fua) {
+		if (wc)
+			q->flush_flags |= REQ_FUA;
+		queue_flag_set(QUEUE_FLAG_FUA, q);
+	} else
+		queue_flag_clear(QUEUE_FLAG_FUA, q);
+	spin_unlock_irq(q->queue_lock);
+}
+EXPORT_SYMBOL_GPL(blk_queue_write_cache);
+
 static int __init blk_settings_init(void)
 {
 	blk_max_low_pfn = max_low_pfn - 1;