linux/kmem: remove HAVE_ATOMIC64_T and kmem_alloc_used wrappers

Seems like we haven't set it since the SPL was pulled into the main ZFS
tree. In removing the define, I've taken the 64-bit version (ie the one
that _hasn't_ been running since back then) because it looks like its
closer to the intended width by the way its used.

Since the macros ar eno longer needed as a selector, pull those too.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Sponsored-by: https://despairlabs.com/sponsor/
Closes #17551

module/os/linux/spl/spl-kmem.c

@@ -302,13 +302,8 @@ spl_kmem_free_impl(const void *buf, size_t size)
 #ifdef DEBUG_KMEM
 
 /* Shim layer memory accounting */
-#ifdef HAVE_ATOMIC64_T
 atomic64_t kmem_alloc_used = ATOMIC64_INIT(0);
-unsigned long long kmem_alloc_max = 0;
-#else  /* HAVE_ATOMIC64_T */
-atomic_t kmem_alloc_used = ATOMIC_INIT(0);
-unsigned long long kmem_alloc_max = 0;
-#endif /* HAVE_ATOMIC64_T */
+uint64_t kmem_alloc_max = 0;
 
 EXPORT_SYMBOL(kmem_alloc_used);
 EXPORT_SYMBOL(kmem_alloc_max);
@@ -320,9 +315,9 @@ spl_kmem_alloc_debug(size_t size, int flags, int node)
 
 	ptr = spl_kmem_alloc_impl(size, flags, node);
 	if (ptr) {
-		kmem_alloc_used_add(size);
-		if (unlikely(kmem_alloc_used_read() > kmem_alloc_max))
-			kmem_alloc_max = kmem_alloc_used_read();
+		atomic64_add(size, &kmem_alloc_used);
+		if (unlikely(atomic64_read(&kmem_alloc_used) > kmem_alloc_max))
+			kmem_alloc_max = atomic64_read(&kmem_alloc_used);
 	}
 
 	return (ptr);
@@ -331,7 +326,7 @@ spl_kmem_alloc_debug(size_t size, int flags, int node)
 inline void
 spl_kmem_free_debug(const void *ptr, size_t size)
 {
-	kmem_alloc_used_sub(size);
+	atomic64_sub(size, &kmem_alloc_used);
 	spl_kmem_free_impl(ptr, size);
 }
 
@@ -595,7 +590,7 @@ spl_kmem_init(void)
 {
 
 #ifdef DEBUG_KMEM
-	kmem_alloc_used_set(0);
+	atomic64_set(&kmem_alloc_used, 0);
 
 
 
@@ -617,9 +612,10 @@ spl_kmem_fini(void)
 	 * at that address to aid in debugging.  Performance is not
 	 * a serious concern here since it is module unload time.
 	 */
-	if (kmem_alloc_used_read() != 0)
+	if (atomic64_read(&kmem_alloc_used) != 0)
 		printk(KERN_WARNING "kmem leaked %ld/%llu bytes\n",
-		    (unsigned long)kmem_alloc_used_read(), kmem_alloc_max);
+		    (unsigned long)atomic64_read(&kmem_alloc_used),
+		    kmem_alloc_max);
 
 #ifdef DEBUG_KMEM_TRACKING
 	spl_kmem_fini_tracking(&kmem_list, &kmem_lock);

module/os/linux/spl/spl-proc.c

@@ -82,11 +82,7 @@ proc_domemused(CONST_CTL_TABLE *table, int write,
 	if (write) {
 		*ppos += *lenp;
 	} else {
-#ifdef HAVE_ATOMIC64_T
 		val = atomic64_read((atomic64_t *)table->data);
-#else
-		val = atomic_read((atomic_t *)table->data);
-#endif /* HAVE_ATOMIC64_T */
 		rc = proc_doulongvec_minmax(&dummy, write, buffer, lenp, ppos);
 	}
 
@@ -315,18 +311,14 @@ static struct ctl_table spl_kmem_table[] = {
 	{
 		.procname	= "kmem_used",
 		.data		= &kmem_alloc_used,
-#ifdef HAVE_ATOMIC64_T
 		.maxlen		= sizeof (atomic64_t),
-#else
-		.maxlen		= sizeof (atomic_t),
-#endif /* HAVE_ATOMIC64_T */
 		.mode		= 0444,
 		.proc_handler	= &proc_domemused,
 	},
 	{
 		.procname	= "kmem_max",
 		.data		= &kmem_alloc_max,
-		.maxlen		= sizeof (unsigned long),
+		.maxlen		= sizeof (uint64_t),
 		.extra1		= &table_min,
 		.extra2		= &table_max,
 		.mode		= 0444,