From 5307e2ad69ab3b0e0622fdf8b254c1d4565eb924 Mon Sep 17 00:00:00 2001
From: Lukas Wunner <lukas@wunner.de>
Date: Thu, 12 Oct 2017 12:40:10 +0200
Subject: [PATCH] bitops: Introduce assign_bit()
Git-commit: 5307e2ad69ab3b0e0622fdf8b254c1d4565eb924
Patch-mainline: v4.15-rc1
References: bsc#1093023

A common idiom is to assign a value to a bit with:

    if (value)
        set_bit(nr, addr);
    else
        clear_bit(nr, addr);

Likewise common is the one-line expression variant:

    value ? set_bit(nr, addr) : clear_bit(nr, addr);

Commit 9a8ac3ae682e ("dm mpath: cleanup QUEUE_IF_NO_PATH bit
manipulation by introducing assign_bit()") introduced assign_bit()
to the md subsystem for brevity.

Make it available to others, specifically gpiolib and the upcoming
driver for Maxim MAX3191x industrial serializer chips.

As requested by Peter Zijlstra, change the argument order to reflect
traditional "dst = src" in C, hence "assign_bit(nr, addr, value)".

Cc: Bart Van Assche <bart.vanassche@wdc.com>
Cc: Alasdair Kergon <agk@redhat.com>
Cc: Mike Snitzer <snitzer@redhat.com>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Neil Brown <neilb@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Borislav Petkov <bp@alien8.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Acked-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Coly Li <colyli@suse.de>

---
 drivers/md/dm-mpath.c  |   22 +++++++---------------
 include/linux/bitops.h |   24 ++++++++++++++++++++++++
 2 files changed, 31 insertions(+), 15 deletions(-)

--- a/drivers/md/dm-mpath.c
+++ b/drivers/md/dm-mpath.c
@@ -637,14 +637,6 @@ static void process_queued_bios(struct w
 	blk_finish_plug(&plug);
 }
 
-static void assign_bit(bool value, long nr, unsigned long *addr)
-{
-	if (value)
-		set_bit(nr, addr);
-	else
-		clear_bit(nr, addr);
-}
-
 /*
  * If we run out of usable paths, should we queue I/O or error it?
  */
@@ -654,11 +646,11 @@ static int queue_if_no_path(struct multi
 	unsigned long flags;
 
 	spin_lock_irqsave(&m->lock, flags);
-	assign_bit((save_old_value && test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) ||
-		   (!save_old_value && queue_if_no_path),
-		   MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags);
-	assign_bit(queue_if_no_path || dm_noflush_suspending(m->ti),
-		   MPATHF_QUEUE_IF_NO_PATH, &m->flags);
+	assign_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags,
+		   (save_old_value && test_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags)) ||
+		   (!save_old_value && queue_if_no_path));
+	assign_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags,
+		   queue_if_no_path || dm_noflush_suspending(m->ti));
 	spin_unlock_irqrestore(&m->lock, flags);
 
 	if (!queue_if_no_path) {
@@ -1583,8 +1575,8 @@ static void multipath_resume(struct dm_t
 	unsigned long flags;
 
 	spin_lock_irqsave(&m->lock, flags);
-	assign_bit(test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags),
-		   MPATHF_QUEUE_IF_NO_PATH, &m->flags);
+	assign_bit(MPATHF_QUEUE_IF_NO_PATH, &m->flags,
+		   test_bit(MPATHF_SAVED_QUEUE_IF_NO_PATH, &m->flags));
 	spin_unlock_irqrestore(&m->lock, flags);
 }
 
--- a/include/linux/bitops.h
+++ b/include/linux/bitops.h
@@ -252,6 +252,30 @@ static __always_inline void set_bit32(lo
 	set_bit(nr, (volatile unsigned long *)addr);
 }
 
+/**
+ * assign_bit - Assign value to a bit in memory
+ * @nr: the bit to set
+ * @addr: the address to start counting from
+ * @value: the value to assign
+ */
+static __always_inline void assign_bit(long nr, volatile unsigned long *addr,
+				       bool value)
+{
+	if (value)
+		set_bit(nr, addr);
+	else
+		clear_bit(nr, addr);
+}
+
+static __always_inline void __assign_bit(long nr, volatile unsigned long *addr,
+					 bool value)
+{
+	if (value)
+		__set_bit(nr, addr);
+	else
+		__clear_bit(nr, addr);
+}
+
 #ifdef __KERNEL__
 
 #ifndef set_mask_bits