locking/local_lock, mm: replace localtry_ helpers with local_trylock_t type

JIRA: https://issues.redhat.com/browse/RHEL-78202

Conflicts:
- conflicts due to already backported commit 7c34b72 ("memcg: drain obj stock on cpu hotplug teardown")

commit 51339d9
Author: Alexei Starovoitov <ast@kernel.org>
Date:   Wed Apr 2 19:55:14 2025 -0700

    locking/local_lock, mm: replace localtry_ helpers with local_trylock_t type

    Partially revert commit 0aaddfb ("locking/local_lock: Introduce
    localtry_lock_t").  Remove localtry_*() helpers, since localtry_lock()
    name might be misinterpreted as "try lock".

    Introduce local_trylock[_irqsave]() helpers that only work with newly
    introduced local_trylock_t type.  Note that attempt to use
    local_trylock[_irqsave]() with local_lock_t will cause compilation
    failure.

    Usage and behavior in !PREEMPT_RT:

    local_lock_t lock;                     // sizeof(lock) == 0
    local_lock(&lock);                     // preempt disable
    local_lock_irqsave(&lock, ...);        // irq save
    if (local_trylock_irqsave(&lock, ...)) // compilation error

    local_trylock_t lock;                  // sizeof(lock) == 4
    local_lock(&lock);                     // preempt disable, acquired = 1
    local_lock_irqsave(&lock, ...);        // irq save, acquired = 1
    if (local_trylock(&lock))              // if (!acquired) preempt disable, acquired = 1
    if (local_trylock_irqsave(&lock, ...)) // if (!acquired) irq save, acquired = 1

    The existing local_lock_*() macros can be used either with local_lock_t or
    local_trylock_t.  With local_trylock_t they set acquired = 1 while
    local_unlock_*() clears it.

    In !PREEMPT_RT local_lock_irqsave(local_lock_t *) disables interrupts to
    protect critical section, but it doesn't prevent NMI, so the fully
    reentrant code cannot use local_lock_irqsave(local_lock_t *) for exclusive
    access.

    The local_lock_irqsave(local_trylock_t *) helper disables interrupts and
    sets acquired=1, so local_trylock_irqsave(local_trylock_t *) from NMI
    attempting to acquire the same lock will return false.

    In PREEMPT_RT local_lock_irqsave() maps to preemptible spin_lock().  Map
    local_trylock_irqsave() to preemptible spin_trylock().  When in hard IRQ
    or NMI return false right away, since spin_trylock() is not safe due to
    explicit locking in the underneath rt_spin_trylock() implementation.
    Removing this explicit locking and attempting only "trylock" is undesired
    due to PI implications.

    The local_trylock() without _irqsave can be used to avoid the cost of
    disabling/enabling interrupts by only disabling preemption, so
    local_trylock() in an interrupt attempting to acquire the same lock will
    return false.

    Note there is no need to use local_inc for acquired variable, since it's a
    percpu variable with strict nesting scopes.

    Note that guard(local_lock)(&lock) works only for "local_lock_t lock".

    The patch also makes sure that local_lock_release(l) is called before
    WRITE_ONCE(l->acquired, 0).  Though IRQs are disabled at this point the
    local_trylock() from NMI will succeed and local_lock_acquire(l) will warn.

    Link: https://lkml.kernel.org/r/20250403025514.41186-1-alexei.starovoitov@gmail.com
    Fixes: 0aaddfb ("locking/local_lock: Introduce localtry_lock_t")
    Signed-off-by: Alexei Starovoitov <ast@kernel.org>
    Acked-by: Vlastimil Babka <vbabka@suse.cz>
    Acked-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
    Reviewed-by: Shakeel Butt <shakeel.butt@linux.dev>
    Cc: Daniel Borkman <daniel@iogearbox.net>
    Cc: Linus Torvalds <torvalds@linuxfoundation.org>
    Cc: Martin KaFai Lau <martin.lau@kernel.org>
    Cc: Michal Hocko <mhocko@suse.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Steven Rostedt <rostedt@goodmis.org>
    Cc: Vlastimil Babka <vbabka@suse.cz>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Signed-off-by: Gregory Bell <grbell@redhat.com>

Author: Gbell26

include/linux/local_lock.h

@@ -52,74 +52,32 @@
 	__local_unlock_irqrestore(lock, flags)
 
 /**
- * localtry_lock_init - Runtime initialize a lock instance
- */
-#define localtry_lock_init(lock)		__localtry_lock_init(lock)
-
-/**
- * localtry_lock - Acquire a per CPU local lock
- * @lock:	The lock variable
- */
-#define localtry_lock(lock)		__localtry_lock(lock)
-
-/**
- * localtry_lock_irq - Acquire a per CPU local lock and disable interrupts
- * @lock:	The lock variable
- */
-#define localtry_lock_irq(lock)		__localtry_lock_irq(lock)
-
-/**
- * localtry_lock_irqsave - Acquire a per CPU local lock, save and disable
- *			 interrupts
- * @lock:	The lock variable
- * @flags:	Storage for interrupt flags
+ * local_lock_init - Runtime initialize a lock instance
  */
-#define localtry_lock_irqsave(lock, flags)				\
-	__localtry_lock_irqsave(lock, flags)
+#define local_trylock_init(lock)	__local_trylock_init(lock)
 
 /**
- * localtry_trylock - Try to acquire a per CPU local lock.
+ * local_trylock - Try to acquire a per CPU local lock
  * @lock:	The lock variable
  *
  * The function can be used in any context such as NMI or HARDIRQ. Due to
  * locking constrains it will _always_ fail to acquire the lock in NMI or
  * HARDIRQ context on PREEMPT_RT.
  */
-#define localtry_trylock(lock)		__localtry_trylock(lock)
+#define local_trylock(lock)		__local_trylock(lock)
 
 /**
- * localtry_trylock_irqsave - Try to acquire a per CPU local lock, save and disable
- *			      interrupts if acquired
+ * local_trylock_irqsave - Try to acquire a per CPU local lock, save and disable
+ *			   interrupts if acquired
  * @lock:	The lock variable
  * @flags:	Storage for interrupt flags
  *
  * The function can be used in any context such as NMI or HARDIRQ. Due to
  * locking constrains it will _always_ fail to acquire the lock in NMI or
  * HARDIRQ context on PREEMPT_RT.
  */
-#define localtry_trylock_irqsave(lock, flags)				\
-	__localtry_trylock_irqsave(lock, flags)
-
-/**
- * local_unlock - Release a per CPU local lock
- * @lock:	The lock variable
- */
-#define localtry_unlock(lock)		__localtry_unlock(lock)
-
-/**
- * local_unlock_irq - Release a per CPU local lock and enable interrupts
- * @lock:	The lock variable
- */
-#define localtry_unlock_irq(lock)		__localtry_unlock_irq(lock)
-
-/**
- * localtry_unlock_irqrestore - Release a per CPU local lock and restore
- *			      interrupt flags
- * @lock:	The lock variable
- * @flags:      Interrupt flags to restore
- */
-#define localtry_unlock_irqrestore(lock, flags)			\
-	__localtry_unlock_irqrestore(lock, flags)
+#define local_trylock_irqsave(lock, flags)			\
+	__local_trylock_irqsave(lock, flags)
 
 DEFINE_GUARD(local_lock, local_lock_t __percpu*,
 	     local_lock(_T),