WHATS_NEW           |  1 +
 lib/device/bcache.c | 10 +++++++++-
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/WHATS_NEW b/WHATS_NEW
index 47db4a3..8063364 100644
--- a/WHATS_NEW
+++ b/WHATS_NEW
@@ -10,6 +10,7 @@ Version 2.02.182 -
   Fix change of monitoring in clustered volumes.
   Fix lvconvert striped/raid0/raid0_meta -> raid6 regression.
   Add After=rbdmap.service to {lvm2-activation-net,blk-availability}.service.
+  Reduce max concurrent aios to avoid EMFILE with many devices.
   Fix lvconvert conversion attempts to linear.
   Fix lvconvert raid0/raid0_meta -> striped regression.
   Fix lvconvert --splitmirror for mirror type (2.02.178).
diff --git a/lib/device/bcache.c b/lib/device/bcache.c
index 6886b74..7384a32 100644
--- a/lib/device/bcache.c
+++ b/lib/device/bcache.c
@@ -253,7 +253,15 @@ static bool _async_issue(struct io_engine *ioe, enum dir d, int fd,
 	return true;
 }
 
-#define MAX_IO 1024
+/*
+ * MAX_IO is returned to the layer above via bcache_max_prefetches() which
+ * tells the caller how many devices to submit io for concurrently.  There will
+ * be an open file descriptor for each of these, so keep it low enough to avoid
+ * reaching the default max open file limit (1024) when there are over 1024
+ * devices being scanned.
+ */
+
+#define MAX_IO 256
 #define MAX_EVENT 64
 
 static bool _async_wait(struct io_engine *ioe, io_complete_fn fn)