From 533ffb67e3e8000a059bc9cc86d678b22888f550 Mon Sep 17 00:00:00 2001
From: Slobodan Predolac <spredolac@fb.com>
Date: Thu, 21 May 2026 14:11:26 -0700
Subject: [PATCH] Refactor arena ctl helpers

---
 src/ctl.c | 95 +++++++++++++++++++++++++++++++++----------------------
 1 file changed, 58 insertions(+), 37 deletions(-)

diff --git a/src/ctl.c b/src/ctl.c
index e048135a..592f764b 100644
--- a/src/ctl.c
+++ b/src/ctl.c
@@ -981,6 +981,21 @@ ctl_accum_atomic_zu(atomic_zu_t *dst, atomic_zu_t *src) {
 
 /******************************************************************************/
 
+static bool
+ctl_arena_ind_is_deprecated_all(size_t i, unsigned narenas) {
+	/*
+	 * Historical compatibility for treating arena.<narenas> as the merged
+	 * all-arenas entry.  New code should use MALLCTL_ARENAS_ALL.
+	 */
+	return i == narenas;
+}
+
+static bool
+ctl_arena_ind_is_all(size_t i, unsigned narenas) {
+	return i == MALLCTL_ARENAS_ALL
+	    || ctl_arena_ind_is_deprecated_all(i, narenas);
+}
+
 static unsigned
 arenas_i2a_impl(size_t i, bool compat, bool validate) {
 	unsigned a;
@@ -993,7 +1008,8 @@ arenas_i2a_impl(size_t i, bool compat, bool validate) {
 		a = 1;
 		break;
 	default:
-		if (compat && i == ctl_arenas->narenas) {
+		if (compat && ctl_arena_ind_is_deprecated_all(
+		    i, ctl_arenas->narenas)) {
 			/*
 			 * Provide deprecated backward compatibility for
 			 * accessing the merged stats at index narenas rather
@@ -2693,6 +2709,40 @@ label_return:
 	return ret;
 }
 
+static void
+arena_i_decay_all(tsdn_t *tsdn, unsigned narenas, bool all) {
+	unsigned i;
+	VARIABLE_ARRAY_UNSAFE(arena_t *, tarenas, narenas);
+
+	for (i = 0; i < narenas; i++) {
+		tarenas[i] = arena_get(tsdn, i, false);
+	}
+
+	/*
+	 * No further need to hold ctl_mtx, since narenas and tarenas contain
+	 * everything needed below.
+	 */
+	malloc_mutex_unlock(tsdn, &ctl_mtx);
+
+	for (i = 0; i < narenas; i++) {
+		if (tarenas[i] != NULL) {
+			arena_decay(tsdn, tarenas[i], false, all);
+		}
+	}
+}
+
+static void
+arena_i_decay_one(tsdn_t *tsdn, unsigned arena_ind, bool all) {
+	arena_t *tarena = arena_get(tsdn, arena_ind, false);
+
+	/* No further need to hold ctl_mtx. */
+	malloc_mutex_unlock(tsdn, &ctl_mtx);
+
+	if (tarena != NULL) {
+		arena_decay(tsdn, tarena, false, all);
+	}
+}
+
 static void
 arena_i_decay(tsdn_t *tsdn, unsigned arena_ind, bool all) {
 	malloc_mutex_lock(tsdn, &ctl_mtx);
@@ -2703,39 +2753,11 @@ arena_i_decay(tsdn_t *tsdn, unsigned arena_ind, bool all) {
 		 * Access via index narenas is deprecated, and scheduled for
 		 * removal in 6.0.0.
 		 */
-		if (arena_ind == MALLCTL_ARENAS_ALL || arena_ind == narenas) {
-			unsigned i;
-			VARIABLE_ARRAY_UNSAFE(arena_t *, tarenas, narenas);
-
-			for (i = 0; i < narenas; i++) {
-				tarenas[i] = arena_get(tsdn, i, false);
-			}
-
-			/*
-			 * No further need to hold ctl_mtx, since narenas and
-			 * tarenas contain everything needed below.
-			 */
-			malloc_mutex_unlock(tsdn, &ctl_mtx);
-
-			for (i = 0; i < narenas; i++) {
-				if (tarenas[i] != NULL) {
-					arena_decay(
-					    tsdn, tarenas[i], false, all);
-				}
-			}
+		if (ctl_arena_ind_is_all(arena_ind, narenas)) {
+			arena_i_decay_all(tsdn, narenas, all);
 		} else {
-			arena_t *tarena;
-
 			assert(arena_ind < narenas);
-
-			tarena = arena_get(tsdn, arena_ind, false);
-
-			/* No further need to hold ctl_mtx. */
-			malloc_mutex_unlock(tsdn, &ctl_mtx);
-
-			if (tarena != NULL) {
-				arena_decay(tsdn, tarena, false, all);
-			}
+			arena_i_decay_one(tsdn, arena_ind, all);
 		}
 	}
 }
@@ -2920,8 +2942,7 @@ arena_i_dss_ctl(tsd_t *tsd, const size_t *mib, size_t miblen, void *oldp,
 	 * 6.0.0.
 	 */
 	dss_prec_t dss_prec_old;
-	if (arena_ind == MALLCTL_ARENAS_ALL
-	    || arena_ind == ctl_arenas->narenas) {
+	if (ctl_arena_ind_is_all(arena_ind, ctl_arenas->narenas)) {
 		if (dss_prec != dss_prec_limit
 		    && extent_dss_prec_set(dss_prec)) {
 			ret = EFAULT;
@@ -2996,7 +3017,7 @@ arena_i_decay_ms_ctl_impl(tsd_t *tsd, const size_t *mib, size_t miblen,
 	extent_state_t state = dirty ? extent_state_dirty : extent_state_muzzy;
 
 	if (oldp != NULL && oldlenp != NULL) {
-		size_t oldval = arena_decay_ms_get(arena, state);
+		ssize_t oldval = arena_decay_ms_get(arena, state);
 		READ(oldval, ssize_t);
 	}
 	if (newp != NULL) {
@@ -3229,8 +3250,8 @@ arenas_decay_ms_ctl_impl(tsd_t *tsd, const size_t *mib, size_t miblen,
 	int ret;
 
 	if (oldp != NULL && oldlenp != NULL) {
-		size_t oldval = (dirty ? arena_dirty_decay_ms_default_get()
-		                       : arena_muzzy_decay_ms_default_get());
+		ssize_t oldval = (dirty ? arena_dirty_decay_ms_default_get()
+		                        : arena_muzzy_decay_ms_default_get());
 		READ(oldval, ssize_t);
 	}
 	if (newp != NULL) {