From 698ab77aebffe08b312fbcdddeb0e8bd08b78717 Mon Sep 17 00:00:00 2001
From: Vivek Goyal <vgoyal@redhat.com>
Date: Wed, 28 Apr 2021 15:03:12 -0400
Subject: [PATCH] dax: Add an enum for specifying dax wakup mode
Git-commit: 698ab77aebffe08b312fbcdddeb0e8bd08b78717
Patch-mainline: v5.13-rc2
References: bsc#1187411

Dan mentioned that he is not very fond of passing around a boolean true/false
to specify if only next waiter should be woken up or all waiters should be
woken up. He instead prefers that we introduce an enum and make it very
explicity at the callsite itself. Easier to read code.

This patch should not introduce any change of behavior.

Reviewed-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Suggested-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Link: https://lore.kernel.org/r/20210428190314.1865312-2-vgoyal@redhat.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Acked-by: Jan Kara <jack@suse.cz>

---
 fs/dax.c |   20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

--- a/fs/dax.c
+++ b/fs/dax.c
@@ -124,6 +124,16 @@ struct wait_exceptional_entry_queue {
 	struct exceptional_entry_key key;
 };
 
+/**
+ * enum dax_wake_mode: waitqueue wakeup behaviour
+ * @WAKE_ALL: wake all waiters in the waitqueue
+ * @WAKE_NEXT: wake only the first waiter in the waitqueue
+ */
+enum dax_wake_mode {
+	WAKE_ALL,
+	WAKE_NEXT,
+};
+
 static wait_queue_head_t *dax_entry_waitqueue(struct address_space *mapping,
 		pgoff_t index, void *entry, struct exceptional_entry_key *key)
 {
@@ -165,7 +175,7 @@ static int wake_exceptional_entry_func(w
  * wake them.
  */
 static void dax_wake_mapping_entry_waiter(struct address_space *mapping,
-		pgoff_t index, void *entry, bool wake_all)
+		pgoff_t index, void *entry, enum dax_wake_mode mode)
 {
 	struct exceptional_entry_key key;
 	wait_queue_head_t *wq;
@@ -179,7 +189,7 @@ static void dax_wake_mapping_entry_waite
 	 * must be in the waitqueue and the following check will see them.
 	 */
 	if (waitqueue_active(wq))
-		__wake_up(wq, TASK_NORMAL, wake_all ? 0 : 1, &key);
+		__wake_up(wq, TASK_NORMAL, mode == WAKE_ALL ? 0 : 1, &key);
 }
 
 /*
@@ -304,7 +314,7 @@ static void unlock_mapping_entry(struct
 	}
 	unlock_slot(mapping, slot);
 	spin_unlock_irq(&mapping->tree_lock);
-	dax_wake_mapping_entry_waiter(mapping, index, entry, false);
+	dax_wake_mapping_entry_waiter(mapping, index, entry, WAKE_NEXT);
 }
 
 static void put_locked_mapping_entry(struct address_space *mapping,
@@ -324,7 +334,7 @@ static void put_unlocked_mapping_entry(s
 		return;
 
 	/* We have to wake up next waiter for the radix tree entry lock */
-	dax_wake_mapping_entry_waiter(mapping, index, entry, false);
+	dax_wake_mapping_entry_waiter(mapping, index, entry, WAKE_NEXT);
 }
 
 static unsigned long dax_entry_size(void *entry)
@@ -596,7 +606,7 @@ restart:
 			radix_tree_delete(&mapping->page_tree, index);
 			mapping->nrexceptional--;
 			dax_wake_mapping_entry_waiter(mapping, index, entry,
-					true);
+					WAKE_ALL);
 		}
 
 		entry = dax_radix_locked_entry(0, size_flag | RADIX_DAX_EMPTY);