bit_spinlock: __always_inline (un)lock functions

The compiler might decide that it is a smart idea to not inline
bit_spin_lock(), primarily when a couple of functions in the same file end
up calling it.  Especially when used in RMAP map/unmap code next, the
compiler sometimes decides to not inline, which is then observable in some
micro-benchmarks.

Let's simply flag all lock/unlock functions as __always_inline;
arch_test_and_set_bit_lock() and friends are already tagged like that (but
not test_and_set_bit_lock() for some reason).

If ever a problem, we could split it into a fast and a slow path, and only
force the fast path to be inlined.  But there is nothing particularly
"big" here.

Link: https://lkml.kernel.org/r/20250303163014.1128035-11-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Andy Lutomirks^H^Hski <luto@kernel.org>
Cc: Borislav Betkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Lance Yang <ioworker0@gmail.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Matthew Wilcow (Oracle) <willy@infradead.org>
Cc: Michal Koutn <mkoutny@suse.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: tejun heo <tj@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Zefan Li <lizefan.x@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 4 insertions, 4 deletions

diff --git a/include/linux/bit_spinlock.h b/include/linux/bit_spinlock.h
index bbc4730a6505..c0989b5b0407 100644
--- a/include/linux/bit_spinlock.h
+++ b/include/linux/bit_spinlock.h
@@ -13,7 +13,7 @@
  * Don't use this unless you really need to: spin_lock() and spin_unlock()
  * are significantly faster.
  */
-static inline void bit_spin_lock(int bitnum, unsigned long *addr)
+static __always_inline void bit_spin_lock(int bitnum, unsigned long *addr)
 {
 	/*
 	 * Assuming the lock is uncontended, this never enters
@@ -38,7 +38,7 @@ static inline void bit_spin_lock(int bitnum, unsigned long *addr)
 /*
  * Return true if it was acquired
  */
-static inline int bit_spin_trylock(int bitnum, unsigned long *addr)
+static __always_inline int bit_spin_trylock(int bitnum, unsigned long *addr)
 {
 	preempt_disable();
 #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
@@ -54,7 +54,7 @@ static inline int bit_spin_trylock(int bitnum, unsigned long *addr)
 /*
  *  bit-based spin_unlock()
  */
-static inline void bit_spin_unlock(int bitnum, unsigned long *addr)
+static __always_inline void bit_spin_unlock(int bitnum, unsigned long *addr)
 {
 #ifdef CONFIG_DEBUG_SPINLOCK
 	BUG_ON(!test_bit(bitnum, addr));
@@ -71,7 +71,7 @@ static inline void bit_spin_unlock(int bitnum, unsigned long *addr)
  *  non-atomic version, which can be used eg. if the bit lock itself is
  *  protecting the rest of the flags in the word.
  */
-static inline void __bit_spin_unlock(int bitnum, unsigned long *addr)
+static __always_inline void __bit_spin_unlock(int bitnum, unsigned long *addr)
 {
 #ifdef CONFIG_DEBUG_SPINLOCK
 	BUG_ON(!test_bit(bitnum, addr));