Merge tag 'for-linus-20190329' of git://git.kernel.dk/linux-block

Pull block fixes from Jens Axboe:
 "Small set of fixes that should go into this series. This contains:

   - compat signal mask fix for io_uring (Arnd)

   - EAGAIN corner case for direct vs buffered writes for io_uring
     (Roman)

   - NVMe pull request from Christoph with various little fixes

   - sbitmap ws_active fix, which caused a perf regression for shared
     tags (me)

   - sbitmap bit ordering fix (Ming)

   - libata on-stack DMA fix (Raymond)"

* tag 'for-linus-20190329' of git://git.kernel.dk/linux-block:
  nvmet: fix error flow during ns enable
  nvmet: fix building bvec from sg list
  nvme-multipath: relax ANA state check
  nvme-tcp: fix an endianess miss-annotation
  libata: fix using DMA buffers on stack
  io_uring: offload write to async worker in case of -EAGAIN
  sbitmap: order READ/WRITE freed instance and setting clear bit
  blk-mq: fix sbitmap ws_active for shared tags
  io_uring: fix big-endian compat signal mask handling
  blk-mq: update comment for blk_mq_hctx_has_pending()
  blk-mq: use blk_mq_put_driver_tag() to put tag

1 files changed, 11 insertions, 0 deletions

diff --git a/lib/sbitmap.c b/lib/sbitmap.c
index 5b382c1244ed..155fe38756ec 100644
--- a/lib/sbitmap.c
+++ b/lib/sbitmap.c
@@ -591,6 +591,17 @@ EXPORT_SYMBOL_GPL(sbitmap_queue_wake_up);
 void sbitmap_queue_clear(struct sbitmap_queue *sbq, unsigned int nr,
 			 unsigned int cpu)
 {
+	/*
+	 * Once the clear bit is set, the bit may be allocated out.
+	 *
+	 * Orders READ/WRITE on the asssociated instance(such as request
+	 * of blk_mq) by this bit for avoiding race with re-allocation,
+	 * and its pair is the memory barrier implied in __sbitmap_get_word.
+	 *
+	 * One invariant is that the clear bit has to be zero when the bit
+	 * is in use.
+	 */
+	smp_mb__before_atomic();
 	sbitmap_deferred_clear_bit(&sbq->sb, nr);
 
 	/*