Merge tag 'md/3.15' of git://neil.brown.name/md

Pull md updates from Neil Brown:
 "Just a few md patches for the 3.15 merge window.

  Not much happening in md/raid at the moment.  Just a few bug fixes
  (one for -stable) and a couple of performance tweaks"

* tag 'md/3.15' of git://neil.brown.name/md:
  raid5: get_active_stripe avoids device_lock
  raid5: make_request does less prepare wait
  md: avoid oops on unload if some process is in poll or select.
  md/raid1: r1buf_pool_alloc: free allocate pages when subsequent allocation fails.
  md/bitmap: don't abuse i_writecount for bitmap files.

1 files changed, 16 insertions, 12 deletions

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 16f5c21963db..25247a852912 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -679,14 +679,9 @@ get_active_stripe(struct r5conf *conf, sector_t sector,
 				init_stripe(sh, sector, previous);
 				atomic_inc(&sh->count);
 			}
-		} else {
+		} else if (!atomic_inc_not_zero(&sh->count)) {
 			spin_lock(&conf->device_lock);
-			if (atomic_read(&sh->count)) {
-				BUG_ON(!list_empty(&sh->lru)
-				    && !test_bit(STRIPE_EXPANDING, &sh->state)
-				    && !test_bit(STRIPE_ON_UNPLUG_LIST, &sh->state)
-					);
-			} else {
+			if (!atomic_read(&sh->count)) {
 				if (!test_bit(STRIPE_HANDLE, &sh->state))
 					atomic_inc(&conf->active_stripes);
 				BUG_ON(list_empty(&sh->lru) &&
@@ -4552,6 +4547,8 @@ static void make_request(struct mddev *mddev, struct bio * bi)
 	struct stripe_head *sh;
 	const int rw = bio_data_dir(bi);
 	int remaining;
+	DEFINE_WAIT(w);
+	bool do_prepare;
 
 	if (unlikely(bi->bi_rw & REQ_FLUSH)) {
 		md_flush_request(mddev, bi);
@@ -4575,15 +4572,18 @@ static void make_request(struct mddev *mddev, struct bio * bi)
 	bi->bi_next = NULL;
 	bi->bi_phys_segments = 1;	/* over-loaded to count active stripes */
 
+	prepare_to_wait(&conf->wait_for_overlap, &w, TASK_UNINTERRUPTIBLE);
 	for (;logical_sector < last_sector; logical_sector += STRIPE_SECTORS) {
-		DEFINE_WAIT(w);
 		int previous;
 		int seq;
 
+		do_prepare = false;
 	retry:
 		seq = read_seqcount_begin(&conf->gen_lock);
 		previous = 0;
-		prepare_to_wait(&conf->wait_for_overlap, &w, TASK_UNINTERRUPTIBLE);
+		if (do_prepare)
+			prepare_to_wait(&conf->wait_for_overlap, &w,
+				TASK_UNINTERRUPTIBLE);
 		if (unlikely(conf->reshape_progress != MaxSector)) {
 			/* spinlock is needed as reshape_progress may be
 			 * 64bit on a 32bit platform, and so it might be
@@ -4604,6 +4604,7 @@ static void make_request(struct mddev *mddev, struct bio * bi)
 				    : logical_sector >= conf->reshape_safe) {
 					spin_unlock_irq(&conf->device_lock);
 					schedule();
+					do_prepare = true;
 					goto retry;
 				}
 			}
@@ -4640,6 +4641,7 @@ static void make_request(struct mddev *mddev, struct bio * bi)
 				if (must_retry) {
 					release_stripe(sh);
 					schedule();
+					do_prepare = true;
 					goto retry;
 				}
 			}
@@ -4663,8 +4665,10 @@ static void make_request(struct mddev *mddev, struct bio * bi)
 				prepare_to_wait(&conf->wait_for_overlap,
 						&w, TASK_INTERRUPTIBLE);
 				if (logical_sector >= mddev->suspend_lo &&
-				    logical_sector < mddev->suspend_hi)
+				    logical_sector < mddev->suspend_hi) {
 					schedule();
+					do_prepare = true;
+				}
 				goto retry;
 			}
 
@@ -4677,9 +4681,9 @@ static void make_request(struct mddev *mddev, struct bio * bi)
 				md_wakeup_thread(mddev->thread);
 				release_stripe(sh);
 				schedule();
+				do_prepare = true;
 				goto retry;
 			}
-			finish_wait(&conf->wait_for_overlap, &w);
 			set_bit(STRIPE_HANDLE, &sh->state);
 			clear_bit(STRIPE_DELAYED, &sh->state);
 			if ((bi->bi_rw & REQ_SYNC) &&
@@ -4689,10 +4693,10 @@ static void make_request(struct mddev *mddev, struct bio * bi)
 		} else {
 			/* cannot get stripe for read-ahead, just give-up */
 			clear_bit(BIO_UPTODATE, &bi->bi_flags);
-			finish_wait(&conf->wait_for_overlap, &w);
 			break;
 		}
 	}
+	finish_wait(&conf->wait_for_overlap, &w);
 
 	remaining = raid5_dec_bi_active_stripes(bi);
 	if (remaining == 0) {