linux-kernel - [PATCH v3 02/15] perf: Split out mlock limit handling

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Message-ID: <20250812104018.541975109@infradead.org>
Date: Tue, 12 Aug 2025 12:39:00 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: tglx@...utronix.de
Cc: linux-kernel@...r.kernel.org,
 peterz@...radead.org,
 torvalds@...uxfoundation.org,
 mingo@...nel.org,
 namhyung@...nel.org,
 acme@...hat.com,
 kees@...nel.org,
 Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Subject: [PATCH v3 02/15] perf: Split out mlock limit handling

From: Thomas Gleixner <tglx@...utronix.de>

To prepare for splitting the buffer allocation out into seperate functions
for the ring buffer and the AUX buffer, split out mlock limit handling into
a helper function, which can be called from both.

No functional change intended.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Link: https://lkml.kernel.org/r/20250811070620.463634790@linutronix.de
---
 kernel/events/core.c |   77 +++++++++++++++++++++++++--------------------------
 1 file changed, 38 insertions(+), 39 deletions(-)

--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -6927,17 +6927,49 @@ static int map_range(struct perf_buffer
 	return err;
 }
 
+static bool perf_mmap_calc_limits(struct vm_area_struct *vma, long *user_extra, long *extra)
+{
+	unsigned long user_locked, user_lock_limit, locked, lock_limit;
+	struct user_struct *user = current_user();
+
+	user_lock_limit = sysctl_perf_event_mlock >> (PAGE_SHIFT - 10);
+	/* Increase the limit linearly with more CPUs */
+	user_lock_limit *= num_online_cpus();
+
+	user_locked = atomic_long_read(&user->locked_vm);
+
+	/*
+	 * sysctl_perf_event_mlock may have changed, so that
+	 *     user->locked_vm > user_lock_limit
+	 */
+	if (user_locked > user_lock_limit)
+		user_locked = user_lock_limit;
+	user_locked += *user_extra;
+
+	if (user_locked > user_lock_limit) {
+		/*
+		 * charge locked_vm until it hits user_lock_limit;
+		 * charge the rest from pinned_vm
+		 */
+		*extra = user_locked - user_lock_limit;
+		*user_extra -= *extra;
+	}
+
+	lock_limit = rlimit(RLIMIT_MEMLOCK);
+	lock_limit >>= PAGE_SHIFT;
+	locked = atomic64_read(&vma->vm_mm->pinned_vm) + *extra;
+
+	return locked <= lock_limit || !perf_is_paranoid() || capable(CAP_IPC_LOCK);
+}
+
 static int perf_mmap(struct file *file, struct vm_area_struct *vma)
 {
 	struct perf_event *event = file->private_data;
-	unsigned long user_locked, user_lock_limit;
 	struct user_struct *user = current_user();
+	unsigned long vma_size, nr_pages;
+	long user_extra = 0, extra = 0;
 	struct mutex *aux_mutex = NULL;
 	struct perf_buffer *rb = NULL;
-	unsigned long locked, lock_limit;
-	unsigned long vma_size;
-	unsigned long nr_pages;
-	long user_extra = 0, extra = 0;
 	int ret, flags = 0;
 	mapped_f mapped;
 
@@ -7063,38 +7093,7 @@ static int perf_mmap(struct file *file,
 		}
 	}
 
-	user_lock_limit = sysctl_perf_event_mlock >> (PAGE_SHIFT - 10);
-
-	/*
-	 * Increase the limit linearly with more CPUs:
-	 */
-	user_lock_limit *= num_online_cpus();
-
-	user_locked = atomic_long_read(&user->locked_vm);
-
-	/*
-	 * sysctl_perf_event_mlock may have changed, so that
-	 *     user->locked_vm > user_lock_limit
-	 */
-	if (user_locked > user_lock_limit)
-		user_locked = user_lock_limit;
-	user_locked += user_extra;
-
-	if (user_locked > user_lock_limit) {
-		/*
-		 * charge locked_vm until it hits user_lock_limit;
-		 * charge the rest from pinned_vm
-		 */
-		extra = user_locked - user_lock_limit;
-		user_extra -= extra;
-	}
-
-	lock_limit = rlimit(RLIMIT_MEMLOCK);
-	lock_limit >>= PAGE_SHIFT;
-	locked = atomic64_read(&vma->vm_mm->pinned_vm) + extra;
-
-	if ((locked > lock_limit) && perf_is_paranoid() &&
-		!capable(CAP_IPC_LOCK)) {
+	if (!perf_mmap_calc_limits(vma, &user_extra, &extra)) {
 		ret = -EPERM;
 		goto unlock;
 	}